eChapters

These are a broad group of plants that have evolved in situations characterized by very high day temperatures and low night temperatures with very low available moisture in the growing medium. Their plant body is modified to conserve moisture with physiological adaptations that help to reduce moisture loss considerably and to survive in hot desert situations or drought conditions. Stems, leaves and roots of these plants are fleshy and rich in watery mucus. The unusual morphological features that these plants have developed to enable them to survive in their harsh native habitats, set them apart from other plants and have given them rarity value when grown as ornamentals. They are hence displayed individually or grown in a rockery where a landscape of rocks and stones highlight their features and at the same time provide desirable contrast with other garden plants. Many members of Cactaceae, Crassulaceae, Aizoaceae, Euphorbiaceae, Asphodelaceae and Agavaceae belong to this group and are commonly referred to as rock garden plants.

Terrestrial or epiphytic members of the family Bromeliaceae that are grown in gardens for their unusually coloured and patterned leaves or showy inflorescences and fruits are referred to as ornamental ‘Bromeliads’. Being low growing, they are ideally displayed in containers or as epiphytes. They are sun loving, suckering in habit and have xerophytic adaptations. The leaves are tough and fibrous often with spiny margins and sheathing leaf bases that hold water. A grayish-white waxy or powdery coating often covers the lamina. Certain bromeliads have a water collecting depression at the center. Inflorescences are sunken, erect or reclining, with condensed or long and much branched stalks carrying colourful bracts and usually, less showy flowers. In many, the terminal leaves become brightly coloured at flowering. These and the floral bracts remain showy even after the flowers are shed.

Ornamental bromeliads popularly grown in gardens include the following:

Aechmea blanchetiana

Copper leaf bromeliad

Plants have strap like leaves that develop streaks of coppery red colour on the upper surface in bright sunlight.

Aechmea burle-marxii

Burle-Marx bromeliad

Pteridophytes such as ferns belonging to several families, selaginellas popularly called ‘club mosses’ belonging to Selaginellaceae and the Lycopods which resemble both these, belonging to Lycopodiaceae are shade loving plants adapted to cool and moist or hot and humid ecosystems of tropical to temperate climates. They are mostly epiphytic or lithophytic and are grown as foliage ornamentals in a fernery or in shaded areas in gardens. Many are favoured indoor plants.

Popularly grown ferns, lycopods and selaginellas of gardens are listed below:

Adiantum capillus-veneris

Adiantaceae

Common Maidenhair fern

Plants are shade loving bushy lithophytes and have delicate looking thin black stems carrying light green oblique-ovate fronds. They are pot grown as ornamental foliage plants.

Adiantum decorum

Syn. Adiantum raddianum

Adiantaceae

Maidenhair fern

Grasses, bamboos, sedges and rushes are plants that are being used increasingly in xeri-scaping and in marsh gardens for getting the benefits of their unusual foliage textures and colours. Their hardiness, stature and canopy frame make them more suited for specimen planting in gardens and landscapes.

GRASSES

Grasses are the most successful of monocots belonging to the family Poaceae that are found the world over. Low growing perennial grasses are used to make attractive lawns in gardens and to provide a desirable turf cover for various situations. A number of species belonging to various genera differing in leaf colour, shape and growth pattern are used for this purpose. Mixtures of different varieties of grasses are also used for making turf having desirable blends of textures and hardiness. Tall bushy grasses having a mound-like or fountain–like habit and fine to velvety surfaces are grown for their textural and architectural features in landscaping. Many are grown as specimen plants for their display value at flowering. In selecting grasses for gardens, their potentially invasive nature is to be taken into account and seed dispersal controlled by timely cutting.

Grass species that thrive in the hot and humid tropics are called warm-season grasses and include Bermuda grass, Carpet grass and St. Augustine grass. Cool season grasses that are adapted to temperate regions and thrive at temperatures of 10 to 20^oC include Blue grass, Fescues and Zoysia.

Ornamental plants that are adapted to an aquatic environment are commonly grown in water gardens and pools. They include those that are entirely submerged or floaters that are free living in the surface water or having roots anchored firmly in the ground beneath and marginal plants that thrive along the edges of water bodies and in shallow water. Spectacular flowering plants like the lotuses and water lilies to plants like the tape grass that are entirely submerged and grass like are grown in natural or structured fresh water habitats throughout the world. Many of these are also inhabitants of aquaria.

Some of the popularly grown water garden plants are listed below:

Acorus calamus

Araceae

Sweet Flag, Vayambu

Plants are rhizomatous herbs adapted to low lying and wet situations. The leaves are closely spaced, distichously arranged and resembling a fan, leathery, dark green, smooth and shiny. The inflorescence is a spadix that emerges from the middle of the terminal leaf. Plants are valued medicinally for their aromatic rhizomes and are also commonly grown as marginals of water gardens.

1.1 WHAT IS PLANT PROPAGATION?

Propagation of plant is defined as multiplication and perpetuation of new individuals from a selected plant having all the characters of the original one. It is the process of increasing the number of plants of a particular species or cultivar. It refers to the multiplication of an individual plant or group of plants, which have specific value to mankind. New plants or new individuals are required for establishing new plantings/new gardens/new orchards.

2.1 INTRODUCTION

Several propagation structures are helpful in propagation of horticultural crops. These structures are helpful for seed germination, rooting of cuttings, layering, grafting etc. and other hardening operations. The structures which facilitate propagation of plants are called propagation structures. Propagation structures are required for propagating plants by seed, cuttings and grafting.2.2

GREENHOUSE

Greenhouse is a structure covered with glass or polythene for protection against adverse climatic conditions as well as to provide optimum environment for growth of the plants. Greenhouse has been used long back by horticulturists as a means of forcing rapid growth of plants and extending the growing season particularly in colder areas. Plants are grown or cuttings are rooted in a greenhouse when the atmospheric condition does not permit for raising them in outdoor conditions. Modern greenhouses are equipped with regulatory mechanisms for controlling temperature, light intensity, air, humidity etc. Plants in green house are grown in the ground bed or bench type raised beds. The size of the greenhouses and dimensions of beds vary according to the need of propagators. Glass covered greenhouses are expensive but they have long life. However, for short-term benefits, plastic covered greenhouses can also be made. Plastic covered greenhouses are lighter than glass covered ones but there is increase in humidity is such houses, especially in winters, which results in undesirable water drops on the plants. It can however be overcome by making adequate ventilation. Polyvinyl chloride (PVC) has also been used in construction of greenhouses but it tends to darken pre-maturely in sunlight. In India, construction of temporarily low-cost poly houses is in fashion for raising nursery of fruit plant in off-season. Such low-cost greenhouses are constructed either on wood or metal framework and are covered with polyethylene sheet of 0.10 to 0.15mm thickness, which is resistant to ultra-violet rays. These houses are equipped with thermostat, cooler or an air conditioner or humidifier etc for rigid control on temperature and humidity. Greenhouses made from fibre glass sheet are more durable than the polythene houses, but are quite expensive. In greenhouses, two types of beds are used for raising seedlings. In greenhouses, the beds may either be prepared on ground itself or raised beds or bench type beds are used. Greenhouse structures vary from elementary home constructed to elaborate commercial installations.

3.1 INTRODUCTION

A nursery is a place, where seedlings, saplings, trees, shrubs and other plant materials are grown under intensive care and maintained until they are ready for final transplanting in the main field. The importance of the best quality planting material as an initial investment is a well-realized factor for persons engaged in horticulture field. So, nurseries have great demand for the production of plants, bulbs, rhizomes, suckers and grafts. But in general, good quality and assured planting material at reasonable price is not available in most of the cases. Nursery is the basic need of horticulture. Plant propagation techniques and practices is the core of horticulture nurseries. The planting materials for horticultural plantations are raised from seeds and vegetative parts. The difficulty of procuring seeds and their rising cost makes it necessary to find means to increase seedling survival and growth.

4.1 INTRODUCTION

The method of propagation in plants may be sexual or asexual. In sexual method of propagation, specialized reproductive cells called gametes are formed by the process of gametogenesis. Fusion of the male and female gametes leads to the development of an embryo and eventually the seed.

4.2 GAMETOGENESIS

The production of male and female gametes is known as gametogenesis. It occurs within microspores and megaspores. It involves only mitosis. It is of two types: (1) microgametogenesis and (2) megagametogenesis.

5.1 APOMIXIS

Apomixis is derived from two Greek words “Apo” (away from) and “mixis” (the act of mixing or mingling). It refers to the occurrence of an asexual reproductive process in the place of normal sexual processes involving reduction division and fertilization. During sexual reproduction, developmental steps occurring inside the ovule produce the female gametophyte (embryo sac) and following a double fertilization event give rise to embryo and endosperm structures. Apomixis can be best described as the reference to the asexual process. In some species, embryo sac is produced not as a result of meiosis and fertilization but by certain asexual processes. The occurrence of such asexual reproductive process in the place of normal seed reproductive processes of reduction division and fertilization is known as Apomixis. Such seedling plants produced in this manner is known as apomicts. ’’Apomixis’’ is used synonymously with ’’agamospermy’’ (Stebbins 1950), referring to the asexual production of seed.

Apomixis (asexual seed formation) is a phenomenon in which a plant bypasses the most fundamental aspects of sexual reproduction—meiosis and fertilization—to form a viable seed. Plants can form seeds without fertilization, and the seed genotype is consistent with the female parent. The development of apomictic technology would be revolutionary for agriculture and for food production as it would reduce costs and breeding times and also avoid many complications typical of sexual reproduction (e.g., incompatibility barriers) and of vegetative propagation (e.g., viral transfer). The application of apomictic reproductive technology has the potential to revolutionize crop breeding. Apomixis is widely distributed among higher plants. More than 300 species belonging to 35 families are apomictic. It is most common in Gramineae, Compositae, Rosaceae and Rutaceae. Among the major cereals maize, wheat and pearl millet have apomictic relatives. Apomixis is reproduction where only one parent passes genes to the offspring (King, 2006). Apomictically produced offspring are genetically identical to the parent (clones).The method is mostly seen in plants, especially flowering plants. Apomixis was defined by Hans Winkler (2008) as the replacement of the normal sexual reproduction by asexual reproduction, without fertilization. Propagation from cuttings or leaves, is not apomixis. Natural replacement of the seed by an asexual method is apomixis.

6.1 INTRODUCTION

The ultimate success of an orchard enterprise largely depends upon the quality and genuineness of planting materials as nursery plants are the foundation of the orchard. Fruit crops, mostly being perennial in nature, call for utmost care in selection of cultivar, quality planting material and adoption of right technology for mass multiplication of planting material. Mistakes committed during the initial establishment of orchards cannot be corrected and will cause serious damage to production and productivity. The variation of scion-wood and rootstock has great bearing on the productivity of an orchard. Thus, it is of immense importance having all plants carefully labelled or otherwise marked. Cuttings taken from the mother plant will grow to have the same genetic qualities as the original plant. This is why the plants resulting from these cuttings are called “clones”. When a stem cutting is taken from a mother plant, the piece of stem will produce new roots if it is properly hydrated. Additionally, some plants can be grown from leaf pieces, or leaf cuttings and these will produce both stems and roots.

Thus, the progeny trees are the basic component for the multiplication of fruit plants and ultimately deciding the quality and productivity of the fruit crops. Hence, it is necessary to stock the true to type and best quality progeny trees.

In asexual methods of plant propagation, plant parts are being used as propagating materials. The plant from which the plant parts are collected is known as mother plant. There is every possibility of transmission of disease or pest which is present in the mother plant to the progeny. The mother plants have to be maintained properly to obtain disease free planting materials so that multiplication of disease/pest can be prevented. Thus, there is a need for the establishment of mother plant block/scion banks.

7.1 INTRODUCTION

Grafting and budding are horticultural techniques used to join parts from two or more plants so that they appear to grow as a single plant. In grafting, the upper part (scion) of one plant grows on the root system (rootstock) of another plant. In the budding process, a bud is taken from one plant and grown on another. The practice of grafting can be traced back 4,000 years to ancient China and Mesopotamia. As early as 2,000 years ago, people recognized the incompatibility problems that may occur when grafting olives and other fruiting trees.

7.2 ROOT STOCK

The part of the graft that provides root system to the grafted plant is known as rootstock. It is, normally, raised by seeds in the seedbed and then, transplanted in the nursery bed for budding and grafting. Rootstocks are also raised in pots and polythene bags.

8.1 INTRODUCTION

Natural methods of vegetative propagation include strategies that the plants have developed for self-multiplication or perpetuation. Natural vegetative propagation is mostly a process found in herbaceous and woody perennial plants, and typically involves structural modifications of the stem, although any horizontal, underground part of a plant (whether stem, leaf, or root) can contribute to vegetative reproduction of a plant. In crops like ginger, turmeric, onion, garlic, gladioli, and dahlia etc. they continue to grow from buds that are present on the surface of the stem. In some plants, like sweet potato adventitious roots can give rise to new plants. In Bryophyllum and Kalanchoe, the leaves have small buds on their margins. On detachment from the plant, they are able to grow into independent plants and they may also start growing into free plants if their leaves were made to grow in the soil. In nature, vegetative reproduction occurs through underground stems, sub-aerial stems, bulbils, leaves and even roots.

9.1 INTRODUCTION

When a new individual arises from a somatic cell without formation of a seed, it is called vegetative propagation. Vegetative propagation occurs naturally (i.e., natural vegetative propagation) in many crops, and profitably exploited in horticulture using either conventional or biotechnological artificial techniques. We shall discuss conventional artificial vegetative propagation in this chapter including cuttings, grafting, budding, layering, suckering, etc. They have been widely used for commercial propagation of fruit trees and ornamental shrubs.

10.1 INTRODUCTION

‘Tissue culture’ is commonly used as a blanket term to describe all types of plant cultures, viz., callus, cell, protoplast, anther, meristem, embryo and organ cultures (George, 1993). It relies on the phenomenon of cell totipotency. The different techniques of culturing plant tissues may offer certain advantages over traditional methods of propagation.

Growing plants in vitro in a controlled environment, with in-depth knowledge of the culture conditions and the nature of the plant material, ensures effective clonal propagation of genetically superior genotypes of economically important plants. Micropropagation has become an important part of the commercial propagation of many plants (George and Sherrington, 1983; and Zimmerman et al., 1986) because of its advantages as a multiplication system (Pierik, 1997 and Razdan, 2003). Several techniques for in vitro plant propagation have been devised, including the induction of axillary and adventitious shoots, the culture of isolated meristems and plant regeneration by organogenesis and/or somatic embryogenesis (Williams and Maheswaran, 1986; and Gautheret, 1985).

Tissue Culture is becoming as an alternative means to vegetative propagation of plants. In vitro growing plants are usually free from bacterial and fungal diseases. Virus eradication and maintenance of plants in virus free stage can also be rapidly achieved in cultures (Sharma, 2016).

Food waste and loss is an enormous issue worldwide. The FAO states that ‘Hunger is still one of the most urgent development challenges, yet the world is producing more than enough food’, but a vast amount of what is produced gets lost on its way from the field to the consumer. According to the FAO, about 30% of cereals, 20% of dairy products, 35% of fish and seafood, 45% of fruits and vegetables, 20% of meat, 20% of oilseed and pulses and 45% of roots and tubers are lost or wasted. Postharvest food loss is defined as measurable qualitative and quantitative food loss along the supply chain, starting at the time of harvest till its consumption or other end uses. Food losses can either be the result of a direct quantitative loss, for example, during the process of harvest or transport or arise indirectly due to losses in crop quality such as undesired sprouting or water loss. Postharvest food loss consists of many factors, which have not changed much in the last 40 years and so postharvest food loss in general has not changed much. Figure 1 illustrates the main reasons for food loss along the supply chain and is based on ‘The food pipeline’ published by Bourne in 1977. Food loss is highest during storage due to pathogens (insects, bacteria and moulds), environmental conditions (e.g. rain, humidity, heat and frost), sprouting and quality loss (rancidity, water loss and saccharification) or animals (rodents and birds). Recently published data for Switzerland have shown that about 53%-55% of the initial fresh potato production and 41%-46% of the initial processing potato production are lost mostly due to pathogen infection, saccharification, water loss of tubers and early sprouting during storage (Buchholz et al, 2018).

Fruits, nuts and vegetables play a significant role in human nutrition, especially as sources of vitamins, minerals, dietary fibre, and antioxidants. Increased consumption of a variety of fruits and vegetables on a daily basis is highly recommended because of associated health benefits, which include reduced risk of some forms of cancer, heart disease, stroke, and other chronic diseases. Both quantitative and qualitative losses occur in horticultural commodities between harvest and consumption. Qualitative losses, such as loss in edibility, nutritional quality, caloric value, and consumer acceptability of fresh produce, are much more difficult to assess than are quantitative losses. Quality standards, consumer preferences and purchasing power vary greatly across countries and cultures and these differences influence marketability and the magnitude of postharvest losses. Postharvest losses vary greatly across commodity types, with production areas and the season of production. Losses of fresh fruits and vegetables in developed countries are estimated to range from 2 percent for potatoes to 23 percent for strawberries, with an overall average of 12 percent losses between production and consumption sites. In contrast, the range of produce losses in developing countries varies widely. Losses at the retail, food-service, and consumer levels are estimated at approximately 20 percent in developed countries and about 10 percent in developing countries (Adel A. Kader and Rosa S. Rolle, 2004 ). Overall, about one third of horticultural crops produced are never consumed by humans. Reduction of postharvest losses can increase food availability to the growing world population, decrease the area needed for production, and conserve natural resources. Strategies for loss prevention include use of genotypes that have longer postharvest-life, use of integrated crop management systems and good agricultural practices that result in good keeping quality of the commodity and use of proper postharvest handling practices in order to maintain the quality and safety of fresh produce.

Postharvest loss of fruits and vegetables is defined as “that weight of wholesome edible product (exclusive of moisture content) that is normally consumed by human and that has been separated from the medium and sites of its immediate growth and production by deliberate human action with the intention of using it for human feeding but which for any reasons fails to be consumed by human.” Not only quantity and quality but even the appearance of fruits and vegetables are affected, and their market value is reduced. Most ‘skin deep’ injuries such as ‘fly speck’ in apples do not affect the edible part. Some infections are not harmful as they occur on inedible parts and can be trimmed off before consumption ego Colletotrichum spots on the outer leaves of cabbage]. Fresh fruits and vegetables are perishable and highly prone to these losses because they are composed of living tissues. These tissues must be kept alive and health throughout the process of marketing. These are composed of thousands of living cells which require care and maintenance (Alao, 2000). The pathological rots are the most serious which is followed by mechanical injury. Pathological rots in combination with mechanical damage cause serious damage to the perishables. Environmental factors such as temperature, relative humidity and oxygen balance most especially during storage are also greatly responsible for damage also environmental conditions such as temperature and humidity are responsible for rendering fruits and vegetables susceptible for pathological attacks (Yahaya and Mardiyya, 2019). Fungi and bacteria are the major pathogens, which cause postharvest diseases in crops leading to about 30 % loss. Normally diseases will be more at improper temperature and relative humidity. Apart from causing disease, pathogens are also involved in ethylene production, which hastens the deterioration of the product.

Postharvest handling is the stage of crop production immediately following harvest, including cooling, cleaning, sorting and packing. The instant a crop is removed from the ground, or separated from its parent plant, it begins to deteriorate. Postharvest activities include harvesting, handling, storage, processing, packaging, transportation and marketing. Losses of horticultural produce are a major problem in the postharvest chain. The diseases which develop on harvested parts of the plants like seeds, fruits and also on vegetables are the postharvested diseases. The amount or extent of damage depends mainly on the pathogen(s) involved, on the condition of the products and the condition of storage. Major tips to avoid postharvest losses include Tips to avoid postharvest losses include assessing maturity, to check your water quality, to check water temperature, avoid injury, keep the produce cool and proper storage.

“Storage” means the phase of the postharvest system during which the products are kept in such a way as to guarantee food security other than during periods of agricultural production at the marketing level, to balance the supply and demand of agricultural products, thereby stabilizing market prices. Grain, which includes dry kitchen ingredients such as flour, rice, millet, couscous, cornmeal, and so on, can be stored in rigid sealed containers to prevent moisture contamination or insect or rodent infestation. For kitchen use, glass containers are the most traditional method. Maturity indices are the sign or indication the readiness of the commodity for harvest. It is the basis for determining harvest date. Postharvest losses occur between harvest and the moment of human consumption. They include on-farm losses, such as when grain is threshed, winnowed, and dried, as well as losses along the chain during transportation, storage, and processing.

In managing diseases of horticultural crops, pathogen quiescence has important implications in timing prophylaxis, the reduction of stresses that trigger the transition of quiescence to aggression, and managing the harvested crop to prolong quiescence to the point at which yield is no longer affected. The inception of pathogen quiescence and its maintenance on or within the host implies a dynamic equilibrium between the host, the pathogen, and their environment. Physiological and physical changes in the host, its environment, or both trigger changes in that equilibrium to permit the pathogen to resume aggression. Microorganisms lying on the host surface constitute a potential latent infection; as can be the case with Botrytis cinerea conidia that are prevented from germinating by antagonistic bacteria on leaf surfaces (William R. Jarvis, 1994). Quiescence can run the spectrum from the ungerminated spore; through symptomless, internal infections; to visible but nonexpanding lesions, such as ghost spot of tomato (Lycopersicon esculentum) to expanding lesions on banana caused by Colletotrichum musae and on avocado caused by C. gloeosporioides.

A latent, dormant, or quiescent parasitic relationship is a condition in which the pathogen spends long periods during the host’s life in a quiescent stage until, under specific circumstances, it becomes active. Epidemiologists might refer to the period from spore landing until the parasitized tissue produces new spores as a latent period (Dov Prusky, 1996). The term “period of quiescence” is referred to differentiate the quiescent parasitic relationship from the latent period. Quiescence can be enforced during the various processes of fungal attack, which suggests that quiescence may or could occur during any of the processes leading from fungal germination to colonization.

Mycotoxins are naturally occurring toxins produced by certain molds and can be found in food. The molds grow on a variety of different crops and foodstuffs including cereals, nuts, spices, dried fruits, apples and coffee beans, often under warm and humid conditions. Mycotoxins can cause a variety of adverse health effects and pose a serious health threat to both humans and livestock. The adverse health effects of mycotoxins range from acute poisoning to long-term effects such as immune deficiency and cancer. A scientific expert committee jointly convened by WHO and the Food and Agriculture Organization of the United Nations (FAO), called JECFA, is the international body responsible for evaluating the health risk from natural toxins including mycotoxins. International standards and codes of practice to limit exposure to mycotoxins from certain foods are established by the Codex Alimentarius Commission based on JECFA assessments.

Mycotoxins are toxic compounds that are naturally produced by certain types of molds (fungi). Molds that can produce mycotoxins grow on numerous foodstuffs such as cereals, dried fruits, nuts and spices. Mold growth can occur either before harvest or after harvest, during storage, on/in the food itself often under warm, damp and humid conditions. Most mycotoxins are chemically stable and survive food processing. Several hundred different mycotoxins have been identified, but the most commonly observed mycotoxins that present a concern to human health and livestock include aflatoxins, ochratoxin A, patulin, fumonisins, zearalenone and nivalenol/deoxynivalenol. Mycotoxins appear in the food chain as a result of mold infection of crops both before and after harvest. Exposure to mycotoxins can happen either directly by eating infected food or indirectly from animals that are fed contaminated feed, in particular from milk.

The potential for significant economic losses from decay caused by postharvest pathogens is greater than is often realized. Harvesting and handling, and the attendant costs for labor and postharvest chemical treatments, can increase the cost of fresh fruits and vegetables several fold from the field to the consumer. Therefore, any produce lost in storage is worth more economically than an equivalent amount lost in the field. Considering economics and the problem of world hunger, it is imperative to understand the importance of postharvest disease and to continually strive to reduce postharvest losses from pathogens. In recent years, many international organizations have identified the necessity of reducing postharvest food losses as an important worldwide goal. While postharvest losses vary from season to season, an average loss of 10% to 30% after harvest is an average estimate. Significantly higher losses are not uncommon in developing countries. The extent of these losses justifies increased research efforts in postharvest pathology (Carl E. Sams, 1994). Chemical treatments and irradiation have effectively reduced the number of microorganisms on various commodities. However, consumer fears associated with chemical residues and the effects of ionizing radiation on fresh produce are forcing the development of alternative protection methods. Also, many pathogens have developed resistance to several commonly used chemicals, while other decaycausing microorganisms currently cannot be controlled by chemicals. Therefore it is better to seek control strategies that will supplement or replace current disease control methods.

A wide variety of fungal and bacterial pathogens cause postharvest disease in fruits and vegetables. Some of these infect produce before harvest and then remain quiescent until conditions are more favourable for disease development after harvest. Other pathogens infect produce during and after harvest through surface injuries. In the development of strategies for postharvest disease control, it is imperative to take a step back and consider the production and postharvest handling systems in their entirety. Traditionally fungicides have played a central role in postharvest disease control. However, trends towards reduced chemical usage in horticulture are forcing the development of new strategies. Controlling or reducing disease relies on integrated crop and postharvest management, with attention to fungicide application, crop hygiene and nutrition, and the management of ripening, to optimise advantages conferred by the plant’s natural resistance factors that prevent and delay disease development. Agricultural production and food distribution systems have evolved over many years to a complex system which allows for nearly year-round supply of most fresh commodities through longterm storage and long distance shipments to consumers. The expectation of year round supplies has resulted in increased challenges for postharvest handling systems. The availability of fungicides for disease management likely played a major role in the evolution of our current system of food distribution (Mitcham, 1999). With the recent loss of registration of many postharvestfungicides and more expected under the Food Quality Protection Act (FQPA), as well as consumer pressure to reduce the amount of chemicals used on food, the challenge to maintain our current system of food distribution increases.

Postharvest food loss has been considered an unavoidable affliction since food storage first began. These losses are much more painful and costlier in terms of money and man-hours. Such losses due to plant parasitic nematodes, in particular, is severe in tropical regions especially in developing countries like India, where proper storage, transmit and marketing facilities are inadequate. In tropical agriculture, increase in production rate is generally low and, by itself, unable to keep pace with the requirements of the increasing population. Hence, such food shortage demands the need to reduce postharvest loss due to nematodes. Postharvest food losses also constitute a vast complex of physical and biological changes, which makes it very difficult to represent in a single figure. As suggested by different sources, an overall loss of at least 10 per cent occurs in the developing countries. However, the magnitude may range from negligible to cent percent in particular nematode species and crop.

In addition to causing direct losses individually, phytonematodes also favour the establishment of secondary, passive micro- organisms like fungi, bacteria, viruses etc. Nematodes cause mechanical wounds, which serve as avenue for the entry of secondary microorganisms (Ravichandra, 2008). This complex association results in severe damage to planting material.

Postharvest diseases due to nematodes can be managed through restricting the movement of infected planting material to uninfected areas; use of uninfected, healthy planting materials; use of treated planting materials; improvements in the cultural practices at the growing site; timely and careful harvesting; use of nematicides both at pre- and postharvest stages; employment of some physical means like heat, radiation etc; improved storage techniques and integration of these methods. By maintaining hygienic conditions during harvest, transportation, storage and packing most of the postharvest damage due to nematodes can be minimized. Of all the methods, however, regulatory measures like quarantine is more practical and effective in restricting the movement of nematode infected plant materials and contaminated soil into a state or country. Contaminated plant material should be treated (hot water or nematicides) to kill the plant parasitic nematodes before planting to prevent the further postharvest damage. These various measures are primarily aimed at either reduction or wiping out of stages of nematode from the site or protection of host from infection or creation of unfavorable host and/or environmental conditions for the nematodes.

Postharvest losses of fruits and vegetables are even higher and are estimated to be 40-50%. Postharvest fruit rotting are a major cause of those losses and are chiefly caused by fungal pathogens after fruit ripening. In a manner similar to foliar diseases that occur in the field, several factors as fungal pathogenicity, host response and environment determine the outcome of host resistance or susceptibility. However, in postharvest diseases fruit ripening is another major component that will determine fruit resistance. The molecular trigger induces the germ tube to differentiate an appressorium. It has been shown that excess nutrients over ride it and protein synthesis is not required once germination has occurred. Protein synthesis during conidium germination and appressorium formation on cellulose membranes were observed (Pathak, 1997). A specific polypeptide (95 kDa) was synthesized only when appressoria matured (a period lasting from 12-24 h after germination). This molecule is involved in the synthesis of the melanin precursor, Scytalone.

Appressoria grown in the presence of cyclohexamide do not mature nor they subsequently differentiate a penetration peg. Appressorium maturation involves the formation of melanin. It has been shown that melanization of appressoria is necessary for formation of a successful penetration peg. The melanin appears to give the appressorium mechanical strength, but pigmentation is only one factor required for penetration competent appressoria. At restrictive temperatures, pigmentation of conidia of C. lagenarium mutants could be restored with dihydroxyphenylalanine without restoration of appressorial competence. Non-pathogenic mutants have been used to determine factors important for pathogenicity. Cutinase production was essential for penetration of papaya fruits. The cutinase produced during infection of papaya fruit by C. gloeosporioides has been purified and characterized as a glycoprotein of 24 kDa. Polyclonal antibodies raised against this enzyme do not cross react with cutinase from Fusarium so/ani, and lesions do not develop when papaya fruits are inoculated with spore suspensions containing the antibody preparation.

Introduction

At the time of inception of CPRI, in the year 1949, India used to produce 1.54 million tonnes potatoes from 0.234 million ha area at an average productivity level of 6.58 tonne/ ha. As per the first advance estimate of the NHB, the potato production in India during 2018-19 was 52.5 million tonnes from 2.18 million ha area at 24 tonnes/ ha productivity. The potato production, area and productivity increased over 7 decades by 34, 9.3 and 3.7 times, respectively. ICAR-CPRI has been adequately recognised by the nation on several occasions for this stupendous contribution. However, potato in India still has to transform from simply a vegetable supplement to serious food security option. Ability of potato to produce highest nutrition and dry matter on per unit area and time basis, among major food crops, made FAO to declare it the crop to address future global food security and poverty alleviation during 2008. Rising number of working couples, rapid rate of urbanization, enhanced tendency of eating out of home, higher disposable income levels of people and important place of potato in fast food items, create an ideal situation for expansion of potato consumption in the near and distant future.

A perusal of various R&D efforts and outcomes in the field of agriculture in general and, more specifically the potato, reveals that “Business as Usual” scenario would not hold much longer. We have to anticipate and get ready to tackle much more complex and diverse future challenges in our respective fields. As the time lag between research and development efforts and the final application/ adoption of the output may stretch over decades, a long term vision and blueprint of action plan is highly important. This chapter attempts to envisage long term state of affairs of potato industry in India and formulate a strategy to fulfil national needs through a well-documented plan to tackle anticipated challenges.

INTRODUCTION

Potatois an important crop for food and nutritional security of India. Itis mainly grown as rabi crop and 90 per cent of itscultivation is confined to northern Indo-Gangetic plains comprisingthestatesof UttarPradesh, WestBengal,Bihar, Punjab and Haryana. Due to climate change, the main potato season is likely to be warmer than the rest of the seasonsof the year and will affect seriously the potato production in India. Climate change is defined by Intergovernmental Panel on Climate Change (IPCC) as a plausible future climate thathas been constructedfor explicitusein investigatingthepotential consequences of climate change. It is the difference in climate over a period of time (with respect toa base line or a reference period) and corresponds to a statistically significant trend of meanclimate or itsvariability persistent over along period of time. Climate change may be due to both natural aswell asanthropogenic factors. Reference periods are typically of three decadesused as climatological baseline period in impacts and adaptation assessments to Global climate model. The future climate minus baseline climate are used for model scenario comparison of most climate variables. Typically a number of fixed time horizons in the future are produced from model output.For example 2020 (2010-2039), 2050 (2040-2069), 2080 (2070-2099). Future climates are estimated through models, called global circulation models, or global climate models (GCM). GCM simulations are carried out by means of a large set of heavy computations. The IPCC TAR reported 7 GCMs for developing climate scenarios while IPCC FAR reported 21 different GCMs.

INTRODUCTION

Potato belongs to a genetically diverse genus Solanum having nearly 235 tuber bearing species. These speciesform a polyploid series ranging from diploids (2n=2x=24)tohexaploids (2n=2x=72), with12 asthebasic chromosome number. There is also arichdiversity within the cultivatedspecies of potato and they were initially grouped under six different species. Later studies, however, recognized those species as land race populations of S. tuberosum, with the eight groups: Ajanhuiri, Andigenum, Chaucha, Chilotanum, Curtilobum, Juzepczukii,Phurejaand Stenotomum(Spooner & Salas, 2006). Thisrich genetic diversity of the species is available in the Andean mountain where potato originated. In India,however, it was quite natural that genetic variability within the locally available material will be meager since, it was introduced here only about 400 years ago. On the contrary, more than 500 differentvarieties existed in India by 1940. This paradoxical situation was primarily due to assigning different local names toasingle variety in different parts ofthe country. The available local varieties in India consisted of both early introductions belonging to either pure Solanum tuberosum ssp. andigenum or their hybrids with S. tuberosumssp.tuberosumas well as later European introductions belonging to S. tuberosum ssp. tuberosum.

INTRODUCTION

India has emerged as second highest producer of potato in the world, after China. The crop has been identified as the most important crop for ensuring food security for the developing countries, and a highly nutritious food providing more calories, vitamins and nutrients per unit area of cropped land than any other staple food. The crop has witnessed phenomenal increase over the seven decades of potato research in India. For a crop which was introduced in the country only in the early 17^th century, and was neither adapted, nor its staple food, the remarkable increase in potato production and productivity is an exceptional achievement of breeding this temperate introduction into the present day potato cultivars.

BREEDING REQUIREMENTS

The table potatoes introduced in India were adapted to long photoperiods of up to 14 hours and crop durations of 140-180 days allowing them to be cultivated only in the hilly regions of India. The unique and diverse agro-climatic condition of the country, comprising of contrasting conditions in the Indian plains, where potato could be grown in the winter months necessitated breeding efforts to develop the potato varieties suitable for the sub-tropical plains and the other potato growing regions. The winters in sub-tropical plains have short photoperiod (with about 10-11 hours sunshine) and the crop duration is limited to 90-100 days because of short and mild winter. Further constraints on photosynthetic activity due to early morning fog, posing a strong limitation on tuber bulking. This is followed immediately by a long hot summer period, which coincides with the post-harvest storage period of potato, creating challenging storage problems. The rapid degeneration of seed stocks, with concomitant decrease in yield due to accumulation of viral diseases and tuber storage and utilization in hot and humid climate thus needed to be addressed, in priority. Besides, these southern, north Bengal and Sikkim hills and the plateau offer agro climatic area specific problems related to the biotic and abiotic stresses prevalent in the regions. Moreover, the unique reproductive biology of the plant made it possible to flower only under the long day conditions of the hills, where hybridization was initiated at Kufri (Shimla), Himachal Pradesh. However, during the initial years, it was not possible to evaluate the breeding progenies in the warmer sub-tropical plains due to the quick degeneration of hill bred progenies and dormancy of hill potatoes.

INTRODUCTION

Potato (Solanum tuberosum L.) is 3^rd most important noncereal food crop in the world, after rice and wheat, and popularly known as ‘the king of vegetables’. Potatoes are considered as a nonfattening, nutritious and wholesome food, which supply important nutrients to the human diet. Tubers contain significant concentrations of vitamin C and essential amino acids. Potatoes can be consumed in many ways, including baking, boiling, roasting, frying, steaming, and microwaving. It is integral part of food and traditional cousins and likely to find more importance in the dietary habit. Potatoes are either consumed directly or they are processed to give products such as chips and French fries, mashed and canned potatoes. Besides being important in human diet, potatoes are also used as animal feed and as raw material for starch and alcohol production. Potato was an occasional dish of the affluent class at the time of independence but now it is the most abundantly consumed horticulture based food by the poorest of the poor in the country. At present about 68% are utilized for table purpose, 7.5% for processing; 8.5% for seed and remaining 16% produce goes waste due to pre and postharvest handling.

INTRODUCTION

Potato (Solanum tuberosum L.) is the most importantnon-grain food crop of the world and is central to global food security, offeringhigher yields in calories per acre thanany grain.More than 2 billion people worldwide are estimated to be dependent on potato for food, feed or income. Global potato breeding concentrates on the objectives of increasing the yields through resistance to various biotic and abiotic stresses along with improving quality traits but the cultivated potato is an auto-tetraploid (2n=4x=48), clonally propagated, highly heterozygous, and suffers acute inbreeding depression. All these characters complicate genetics/genomic studies as well as breeding efforts to improve important traits such as disease/pest resistance, processing quality and nutritive value.This has lead to the need of high quality, well annotated genome sequence of potato along with high resolution mapsfor aiding the identification of allelic variants for important agronomic traits in potato. Multiple linkage maps have beenconstructedfor potato usingvarious molecularmarkers like RFLPs, AFLPs and SSRs in an effort to develop markers for marker assisted breeding and facilitate map based cloning. These earlierefforts got unequivocal boost when an internationalcollaborationof13countriesviz.Argentina, Brazil,China, Chile, India, Ireland, The Netherlands,New Zealand, Peru, Poland, Russia, the United Kingdom and the United States came together to form the Potato Genome Sequencing Consortium (PGSC) with aim to decipher the potato genome (Xu et al., 2011). The potato genome sequence has provided a major boost to gaining a better understanding of potato trait biology, underpinning future breeding efforts. This would greatly help in enhancing the breeding techniques by implementing the genome assisted methods for imparting the greatertolerance to various biotic and abiotic stressesand ultimately increasing the yields. The knowledge of the complete genome sequence is an invaluable resource for the identificationof genes and variant/novel alleles of genes for everytrait ofinterest to potato breeders. This is very much required for feeding the ever burgeoning global population.

INTRODUCTION

Potato is a vegetatively propagated crop mainly through tubers. Seed is the costliest input, which constitutes nearly half of the production cost. Due to the high cost of seed, seed replacement rate is low, which results in build up of various tuberborne diseases.To maintain high tuber yield, multiplication is done through “Seed Plot Technique” (SPT), which involves seed production in low aphid pressure period to minimize transmission of viruses and also adopt a set of cultural practices aimed at minimizing disease spread. The production of healthy seed tubers through SPT is expensive and the low rate of tuber multiplication (normally 68 times) provides only a limited quantity of quality tubers. Further, the low aphid areas suitable for producing healthy seed in the country lie in the northern plains and high hills (> 1800 m above mean sea level). Changing climate scenario is likely to shrink the window for potato cultivation and increase pathogen/vector attacks across the country thereby seriously limiting quantity and quality of seed in the country. An alternative technology of true potato seed (TPS) or use of botanical seed has shown great potential for producing both diseasefree healthy (quality) and cheaper planting materials for commercial potato production. This chapter describes the classical TPS technology and two novel potential TPSbased technologies in potato propagation.

INTRODUCTION

Potato is a highly versatile crop grown in varying environmental conditions viz. plains, hills and plateau in India. It is grown under short days (SD) in the plains in autumn season and under long days (LD) during summers in hills. Therefore, the pattern of growth, duration of crop as well as the yield varies according to the environment. Besides, the potato cultivars differ from each other in relation to their morphological characters, response to the environmental factors and finally in yield and the dry matter accumulation. The biochemical reasons for such variations are not clear, but it seems that genetically determined differences in the synthesis of growth regulators such as auxins, cytokinins, gibberellic acid (GA) and abscissic acid (ABA) play an important role and their proportion at different growth stages affect the growth and development and thus, the yield of the cultivar (Minhas and Singh, 2003).The present chapter deals with the physiologicalfactors, which determine the growth, development and yield of potato crop.

INTRODUCTION

Potato (Solanum tuberosum L.) is one of the major food crops whichrecorded total globalproduction of 388.1million metrictonnes(mt) in 2017-18. Out of the major staple food crops, potato production (388.1mt) is exceeded only by maize (1077.98 mt), wheat (761.88 mt) and rice (494.88 mt) (FAOSTAT, 2017). According to the three years (2012-2014)averages,globally, India ranks 3^rdin area and 2^ndin terms of production nextto China. Thenutritional quality, high productivity and acquiescence for inclusion in intensive cropping systems of this shortduration crop reflects its great potentialin modern agriculture to feed theexponentiallyrisingpopulationin the developingcountries. But, theintensive cultivation of potato crops urges increased use of fertilizers, pesticides and other chemicals leading to high input costs with plateauingyields. Blanket dose of fertilizers as well as imbalance use of nutrientsnot only increases the cost of farm inputs but also degrades soil condition and causes severe environment pollution. Indiscriminate use of insecticide as well as fungicide is verycommon in potato crop which contaminate the environment and deteriorate product quality. Therefore, the chemical inputs need to be optimised based on actual requirement of the crops for sustainable crop production. Furthermore, potato production is associated witha high tillagepractices, number of tillage operation would depend on soiltype, previous crop etc.

INTRODUCTION

Agricultural biodiversity is the basis ofglobal food security. Wide variety of crops, soil and cropping systems are nurtured by human culturaldiversity since times immemorial. Potatois a majorfood crop which is widely acknowledged now. It is consumed by the world’s largest population than any othervegetable, produces more calories and protein per unit of land and time than any other food crop.Potatohas much potentialfor sustainable, non-chemical farming, fits well with many crop rotations,and does very wellwith naturalfertilizers. Over the years chemical based farming has started experiencing reduced production and increased costs, orboth (Singh et al.,2011 and Sreenivasa et al., 2010). Monoculture of crops such as rice, wheat and cotton etc., depletes topsoil of nutrients and reduces diversity of beneficial microbes leading to reduced soil productivity. It is finally making the crop plants vulnerable to parasites and pathogens. Environmental pollution caused bychemical fertilizers and pesticides is posinga serious threat worldwide (Doranet al., 1996). Healthy soil is the foundation upon which sustainable agriculture is built. Farming practices differ mainly based on soil inputs and crop protection measures (Devarinti,2016).Thusthere is growinginterestinorganicallyproducedproducts and farmers are shifting from conventional to organic farming. In India, Sikkim is the firststate where completelyorganic farmingis adopted. Farming practices differ mainly based on soil inputs and crop protection measures (Devarinti, 2016) in different regions. Different types of farming based on use of natural products are described in the chapter.

INTRODUCTION

Control of weeds below economic threshold level in potato crop is a substantial component of crop management strategy for achieving optimum productivity. In our country, potatoes are raised eitherin assured irrigation or as rainfedcrop with comparatively heavy doses of fertilizers. Therefore, weedsarebound to become menaceduringactive cropgrowth period of this cropand theseundesired plants needs to be controlled in early stages of crop growth by adopting several techniques. Current scenario of crop production is different from past due to manyreasons. Farm holdings are becoming smaller day-by-day and majority of potato growers are small and marginal farmers. They have limitedcapacity for purchase of inputs and farm machines. They need economical, efficient and easier to adopt weed control technologies.Farm labour is also costly nowin many regions as they are migrating towards cities and industrial townships. This scenariobecomes more complex as weeds would be major challenge due to global warming, which is slowly changingclimatesof potato growingregions in India.Theconcern forenvironmentalissuesemphasizeuponadoptingsystems and integrated approach for managing weeds in such away that thesedo not reducethe potato and system productivity (CPRI, 2014).

INTRODUCTION

Information is power in the present age of rapid technological innovations; since information technology (IT) empowers people. IT emerged as the major driver of growth in all walks of life during last quarter of 20^th century and is currently in a steady growth trajectory. It encompasses almost all human endeavors including agriculture. IT can facilitate agriculture in two broad ways; (i) as a tool for direct contribution to agricultural productivity and (ii) as an indirect tool for empowering farmers to take informed and quality decisions which will have positive impact on the way agriculture and allied activities are conducted. Precision farming extensively uses IT to make direct contribution to agricultural productivity. The indirect benefits of IT in empowering Indian farmer are significant and remains to be exploited. The emerging scenario of a deregulated agriculture under WTO has brought about a greater ‘need’ and urgency to make IT an integral part of decision making by agriculture sector. The changing environment faced by Indian farmers makes information not merely useful, but necessary to remain competitive. The farmer urgently requires timely and reliable sources of information inputs for taking decisions. At present, the farmer depends on trickling down of decision inputs from conventional sources, which are slow and unreliable. Besides, the personnel who work for the welfare of Indian farmers, such as extension workers, do not have access to latest information, which hinders their ability to serve the farming community effectively. IT will constitute the primary resource in agri-clinics, agri-business centers, kisan call centers, agri-nukkads, etc. that have been launched by Government of India and other organizations to ensure inclusive growth. Potato is an input-intensive crop and IT will have a special role in making its cultivation more productive and profitable.

INTRODUCTION

Potato ranks third among the major food crops after wheat and rice in the world. It is most important and versatile food of the world. India is second largest potato producer next to china.Potatois bulky and watery in nature and requires lot of energy for production and processing. It is a shortduration crop of 90-120 days, having highest yield per ay per unit area as compared to other major crops. Being a relatively short duration crop in the plains of India, its mechanization assumes a special importance in order to accomplish various farmoperations inverylimited time foritshigherproduction.Manualproduction of potato is time consuming and tedius job, it requires about 1600-2000 man-hours per hectare. With the rising cost of production and depleting energy reserves, increase in crop productivity with minimum input of energy and cost one of the paramount concerns (Garg and Singh 2002). Sustenance of agriculturalproductivitygoes handin handwith mechanization of differentfarm operations, which aims at achieving timeliness of operations, efficientuseof inputs safety and comfort of farmers, reduction in cost of produce and drudgery of farmers (Verma et. al, 1992).With the emergence of new crop rotations and enhanced cropping intensity, many farmers experience scarcity of time and labour. Mechanization plays an important role in timely completing farm operations involved in potato production. It implies a resource management strategy to increase productivity and economic returns. Efforts have been made at various levels to mechanise both production and processing. Various mechanical tools, implements and machinery have been developed for land development, fertilizer application, planting, weeding, harvesting, preparation for storage and on-farm processing of potato (Singh and Gulati 2014).

INTRODUCTION

Potato is an important horticultural food crop which has the potential to meet food demand of the fast growing human population across the world, including India. This is going to be the future food crop for the millions especially in the third world countries. However, this crop is highly prone to wide range of diseases and pests that are considered to be the main bottle neck in potato production across the globe. Amongst the biotic stresses, late blight caused by oomycete Phytophthora infestans (Mont.) de Bary has historically been an important disease of potatoes and tomatoes worldwide. In the mid 1800, late blight caused widespread crop failures throughout Northern Europe including Ireland where it was responsible for the Irish famine. Since then, it has spread far and wide and now occurs wherever potatoes are grown. Losses due to P. infestans have been estimated to € 12 billion per annum of which the losses in developing countries have been estimated around € 10 billion per annum (Haverkort et al., 2009). In India, average annual losses to the tune of 15% have been estimated which amounts to 7.95 million tons of potatoes (Current production is 53 MT). Disease appears every year in epiphytotic form in hilly regions whereas in the plains, although it usually appears every year but its intensity is low (traces to 25%). It is only in few years that it assumes epiphytotic form leading to crop losses to the tune of 40%. Recently, late blight has become a serious problem in kharif grown potatoes and tomatoes in Karnataka state (Sharma et al., 2015). Phytophthora infestans is considered as re-emerging pathogen due to regular emergence of its novel strains with increased virulence and its appearance in new locations with surprising intensity. Management of this devastating pathogen is challenged by its remarkable speed of adaptation to control strategies such as genetically resistant cultivars.

INTRODUCTION

Potatois theworld’s most importantnon-grain foodcommoditythatranks fourth as main food crop in the world after rice,wheat and maize. The crop is grown inmorethan 100 countries, mainly in Asia (195.67 million tons)and Europe (121.76 million tons)(yieldin 2017 as per FAOSTAT, 2019). Because of its efficiency in producing high dry matter, energyand edibleprotein per unit area per unit time, it holds promise for food security in the scenario of ever growing world population. The full potential of this crop however, can onlybe realized if diseases and pests are kept under control, especially in asubtropical country like India, wherethe weather is highly conducive for a number of pathogens.

A number of soiland tuber borne diseases are known to affectthe potato crop causing heavy yield losses. These diseases not only reduce quality and market value of the producebut also spread to new un-infested fields through infected seed potato tubers. Diseasessuch as black scurf, common scab and powdery scab disfigure potato tubers and reduce their market value whereas dry rot, charcoal rot and softrot spoilthe harvested produce during transitand storage. Potatowart is a serious disease which once established is difficult to eradicate and thus require quarantine measures. Bacterial wilt or brown rot of potato is another serious disease which is likely to threaten potato cultivation with the rise in globaltemperature and requires immediate attention.

Potato is becoming a more and more important foodstuff in the world and therefore, its cultivation is expanding fast especially in developing countries. This intensivecultivation, in fact, has led to the emergence of diseases in certain areas where they were of less importance in the past. For instance common scab, known to be a minor disease about2-3 decades ago, is now emerging as serious problem in many potato growing areasof the country including Indo Gangetic plains. Similarly brown rot/bacterial wilt which was endemic in mid hills and plateau region, has now become a limiting factor for potato cultivation in many areasin Madhya Pradesh, West Bengal, north eastern region and in Kumoan hills of Uttrakhand. Sclerotium wilt on the other hand has shown upward trend in plateau region especially in Karnataka. This is because the dynamics of pathogens keeps on changing over time and space and also with the changing farming practicesof a region. Many such new diseases are likely to emerge in a big way in future also, hence warrants regular and careful monitoring. In the following pages, the majorsoiland tuberbornediseases are discussed with special reference to India.

INTRODUCTION

Potato (Solanum tuberosum L.) is afflicted by many kinds of viruses and their various strains belonging to different taxonomic groups (Table 1) throughout the world resultingin declinein yieldand tuber quality. Exact estimation of yield and economic losses caused by potato viruses depends on a number of factors mainly strain of the virus, variety, seasonand growingconditions etc. Generally crop losses ranges between 5 to15 per cent if all plants are secondarily infected with PVX and PVS; 15-30 per cent for 100 per cent secondary infection of PVYnand 40-70 per cent due to PLRV. Besides, in Europe and North America Potato spindle tuber viroid (PSTVd) is wellknown to reduce yieldssignificantly (16-64 per cent) dependingon the viroid strain/potato varietyand warmweather (Singh, 1988). Thesevere strains of Potato virus Y (PVY)and Potato leafroll virus (PLRV) have the potential to reduce yield up to 80 per cent, while mild viruses like Potato virus X (PVX), Potato virus S (PVS)and Potato virus M (PVM) can cause up to 30 per cent yield loss in infected plants. Atospovirus Groundnut bud necrosis virus (GBNV) causing severe stem/leaf necrosis disease in plains/plateaux of central/western India heavily infects the early crop of potato. Similarly, a whitefly transmitted begomovirus Tomato leaf curl New Delhi virus-potato (ToLCNDV) known to cause apical leafcurl disease in India, has become a serious problem in North Indian plains.

The viruses can be mechanically transmitted with plant sap, by contact and with seeds. Infectedtubers, whitefly and aphid vectors are importantfactors for the transmission of the virusesin nature. Potatoviruses are transmitted by aphids in two ways. The viruses are either non-persistent (stylet-borne) or persistent and circulative (they are ingested and persist in the aphid throughout its life cycle). The most common persistent and circulative virus affecting potatoes in India is PLRV. Common non-persistent or stylet-borne viruses are PVY, PVA, PVS and PVM. Control of circulative viruses by insecticides is highly effective, which is not the ease with stylet borneviruses. Sustainable potato production is possible only if the virus incidenceis kept under check especially in sub tropics where the weather is highlyconducive both for vectors and the common viruses. In thischapterthe major viruses and viroidof potato including symptomatology, diagnostics and their management have been discussed.

INTRODUCTION

Insect pests cause variable and complex problems for potato farmers. Insect pests account for 16% of the crop losses of potato worldwide, and reductions in tuber yield and quality can be between 30% and 70% for various insect pests. India has a greatdiversity of insect pests that attack potato. Thesepests can damage potato plants by feeding on leaves, reducing the photosynthetic area and efficiencybyattacking stems, weakeningplants and inhibitingnutrient transport, and by attacking the potato tubers destined for consumption orfor use as seed. In India, approximately 60 billion rupees (US$1.2 billion)worth of potato tubersare lost annually due to pest damage, which accountsfor 10–20% of total production (Chandel et al., 2013). The potato pests are grouped into soil pests, foliage feeders, sap feeders, and storage pests. Inseed production, aphids and whiteflies are of greatest concern. In ware production, the key pests may be insects which attack tubers, such as tubermoth, whitegrubs, and cutworms. In some situations, foliage feeders suchas noctuid moths and coccinellidbeetles are also important.The Potato cyst nematode (PCN) (Globodera spp.) and root knot nematodes (RKN) (Meloidogyne spp.) are amongst the most economicallyimportant nematode pests of potato. Cyst nematodeshave amazing adaptation for long term survival in the soil, even in the absence of a suitable host whichmakesthemchallenging to the farmers, scientists and policy makers. They are subjected to stringent quarantine and/or regulatory procedures, wherever they occur and presents a serious threat to domestic and international commerce in potatoes. RKNs are prevalent all over the world and can cause significantcrop loss in both warmand cool climatic conditions, depending on their species. In this chapter, the current information on biology, ecology and management of the major potato pests is discussed in the Indiancontext.

INTRODUCTION

India is the second largest producer of potato in the world contributing about 12.52%of production from 11.29 % area under potato with an average yield of 22.31 t/ha. Potato is grown in almost allthe states in India under diverse agroclimatic conditions. About 90% of the total potato area is located in the subtropical plains, 6% in the hills and 4% in the plateau region of the peninsular India. Indo-Gangetic plains account for about 76% of the potato area and about 87% of the potato production in the country. Availabilityof assured qualityseed is the most important production constraint in all the potato growing regions of the country.

Seed is the basic vital input in agriculture and its timely availability in adequate quantity as per demand decides the strength growth of agricultural economy in the country. Seed has played a very important role in India’s green revolution and shallcontinue to be the importantcomponent in the days to come. There is a saying “as you sow, so shall you reap”, which traditionally relates to the quality of seed determining the production, has been the wisdom of our forefathers. The traditional farmers’ practices are to save their own seeds generally selected from healthy plants from fields which are freefrom diseases pests, harvest them separately, clean, cure and then store in containers and inspect regularly for any kind of damage; or they get quality seed from other seed producing farmers onbarter basis, indicating thereby the importance of seed in their production system.

INTRODUCTION

Potato production in India has shown a steady increase in the past, presently making the country second largest potato producer in the world. As per the latest available data, during 2018-19, approximately 52.5 million metric tons of potatoes have been produced (NHB, 2019). Increase in production, often resulting in gluts at harvest, has led to several post-harvest problems like storage and proper utilization of the produce. About 90% of the potato crop in the countryis harvested during January-February in the Indo-Gangetic plains comprising the states of Punjab, Haryana, UP, Bihar, West Bengal, MP and Gujarat where the harvest is followed by rising temperatures of hot and dry summer, and further by warm and humid rainy season. Since potato tubers contain about 80% water, under such circumstances, a semi-perishable commodity like potato, cannot be stored for more than 3-4 months without refrigeration because of very high losses due to shrinkage, sprouting and attack by microorganisms.

Therefore, potatoes are mostly stored in refrigerated cold stores maintained between 2-4^oC and 90-95% relative humidity (RH). Low temperature storage has advantages of natural control of sprout growth, low evaporative losses and minimum risk of diseases and pests. These conditions are ideal for storage of seed potato but these cause cold-induced sweetening leading to excessive accumulation of sugars in most of the potato cultivars making them unfit for processing due to browning in chips. Also, such tubers are less preferred for consumption because of sweet taste. Hence, potatoes meant for processing are either stored under non-refrigerated conditions for short term or stored at 10-12^oC with the use of some sprout suppressant like CIPC (isopropyl N-(3chlorophenyl) carbamate) to minimize the accumulation of reducing sugars. The chips produced from such tubers are light in colour.

Potato processing on the other hand is essential to sustain the increasing potato production in the country and to provide proper remuneration to the cultivators. Potatoes can be processed into a variety of products. Potato chips, French fries and dehydrated chips are the most popular processed potato products in the organized and unorganized sectors. The present chapter deals with postharvest management of potatoes in terms of dormancy and sprouting issues and storage technologies for seed, table and processing potatoes. Besides, areas suitable for growing processing potatoes in the country, potato processing scenario in the organized and unorganized sectors are also discussed.

INTRODUCTION

Potato plays a vital rolein foodsecurityworldwide. It is the third most important food crop, afterrice and wheat. It is a nutrient-rich crop which provides more calories,vitamins and nutrients per unit area than any otherstaple crops. FAO declared potato as the crop to address future global food security and poverty alleviation during2008. In Indian agriculture, potatoplays a very important role as it alone contributes about 21 percent of the total vegetable area and 26 percent of total vegetable production of India (DAC&FW, 2017a). As per FAOSTAT data for the year 2017,India with48.6 million t is ranked second in potato productionin the world, onlybehind Chinawith 99.2 million t (Figure 1).

Precision farming is also known as precision agriculture. A farmer is not only expected to produce more for the increasing population and his family but save and protect the fragile environment while practicing it. Advanced technologies with appropriate and exact inputs such as precision farming can take care better of environment. Precision farming is right farming operations at right time leading to maximize profit. Every farming activity performed with precision by doing the right thing, in the right place, in the right way, at the right time and with right technology leading to maximize profit is known as precision farming. It is an efficient, eco-friendly and accurate management of agriculture inputs such as water, seed, fertilizers, pesticides and harvesting tools and machinery to maximize profit and reduce waste. The basic concept of precision farming is to match agricultural inputs and operations as per crop (variety/hybrid/cultivar) and agroclimatic conditions with accuracy to their better use efficiency. Perfection (nothing requisite is wanting) in farming is the key to precision farming.

Precision farming is based on global positioning system (GPS). The unique character of GPS is precision in time and space. Its use is spreading to all farm operations. Precision farming is an integrated information and production based farming system that is designed to increase long term, site specific and whole farm production efficiency, productivity and profitability while minimizing, waste and unintended impacts on the environment. This concept of precision agriculture is based on observing, measuring and responding to inter and intra field variability in crops.

Farm management strategy is the key to precision agriculture that uses integrated smart technologies such as sensors, GIS, GPS, satellite radars, drones, IoT (Internet of things) and data analytics to develop informed crop production and management decisions. The field variations are precisely measured with the help of technologies to optimize applications of inputs such as manures, fertilizers, pesticides, bio-agents and water use to increase crop yield at minimum cost. The aim of precision farming is to increase productivity, decrease production costs and minimize the environmental impact of farming.

It is a common knowledge that most of the farmers apply irrigation water until all the points in the field are fully wetted and covered with a thin sheet of water. Studies have indicated that a significant (20-25%) amount of irrigation water is lost during its application at the farm due to poor farm designing and unevenness of the fields. This problem is more pronounced in the case of rice fields. Unevenness of fields leads to inefficient use of irrigation water and also delays tillage and crop establishment options. Fields that are not levelled have uneven crop stands, increased weed burdens and uneven maturing of crops. All these factors tend to contribute to reduced yield and produce quality which reduce the potential farm income. Effective land levelling is meant to optimize wateruse efficiency, improve crop establishment, reduce the irrigation time and effort required to manage crop.

Reasonably levelled agriculture fields has advantage over uneven and undulating crop fields as unevenness of the soil surface has a significant impact on the seed germination, crop stand and its yield. Traditionally land levelling was being done throughout India by bullock drawn plough or tractors and applying different devices for levelling the field by visual assessment e.g. on small plots with hoes, or with draft animals and equipment such as ploughs and bars or scrapers or grading. Equipment such as grading blades and hydraulically operated levellers mounted on wheels are used with tractors. More advanced and sophisticated levelling equipment is operated with a laser emitter, a laser sensor or receiver, and a scraper pulled by a tractor. After the desired level or slope of the field and/or the difference of the high and low spots have been surveyed, the emitter is set to send a rotating laser beam creating a plane of laser light above the field surface. The laser light is used as the levelling reference. It directs the hydraulic system of the moving tractor and scraper, and thereby controls the levelling. Hence, laser levelling or laser land levelling is levelling the crop field within certain degree of desired slope using a guided laser beam throughout the field.

Sowing of Seed: It is a process of planting seeds of crops in well prepared or no till field or nursery beds/pots for raising crops in following methods:

Methods of Sowing: The sowing method is determined by the crop to be sown and resources on the disposal of farmer. There are 6 sowing methods which differ in their merits, demerits and adoption. Those are:

1.Broad casting

2.Broad or Line sowing

3.Dibbling

4.Transplanting

5.Planting

6.Putting seeds behind the plough.

Seedling:A seedling is a very young plant that grows from a seed. When the moisture, light, and temperature conditions are correct, the seedling’s development begins with seed germination and the formation of three main parts:

1.Radicle - Embryonic root

2.Hypocotyl - Embryonic shoot

3.Cotyledons - Seed leaves.

In vegetables and annual ornamental crops where generally seed size is small they are germinated in nursery beds or in plug trays indoor (greenhouse) or outdoor(field), hardened before transplanting.

Sapling: A sapling is a young tree, say more than 1 year and less than 3 years’ old. In the life cycle of trees, a seedling converts into a sapling as the next stage of development. It is nearly one-meter tall and generally remains to be known as a sampling until its stem reaches 7 centimetre in diameter. The time period of this stage depends upon the particular species of a tree. In vegetable and annual ornamental crops seedlings generally are one month to 40 days old. Older than this, seedlings do not give better yields on transplanting. Very young seedlings exhibit larger mortality on transplanting.

Transplanting: Transplanting or replanting is the technique of moving a plant by uplifting from one location to another. From nursery beds seedlings or saplings are shifted and planted either in the field or greenhouses for commercial growing. Seedlings are uprooted if grown in soil medium. They are transplanted with growing medium. Uprooted seedlings take time to establish at a new place and face transplanting shock- time taken by roots to establish contact with the soil or growing medium.

In soil culture, also known as in-ground culture, crops are raised on level ground as well as in raised beds. Soil culture is more often used in growing vegetables (e.g., tomatoes, lettuce, cucumbers, and peppers) rather than ornamental crops such as herbs, roses, freesia, and foliage plants as well as popular with smaller commercial and organic growers. The soil should be well drained, fertile, have a medium to light texture and be high in organic matter. The soil in a greenhouse should be worked as deeply as possible to break any existing hardpans or those that may have developed because of repeated traffic over the area. Fumigation or pasteurization of the soil is a must before each crop or at least once a year. This will help to destroy disease, nematodes and weeds. If soil is steamed, hold it at 180 degrees F (82°C) for 4 hours. Production techniques used in soil culture are similar to intensive crop production methods used in the field. Although soil is readily available at most places where a greenhouse is located most commercial growers, no longer rely on soil culture in the greenhouse as they did ealier. Some of the reasons include insect and disease pressures and costly fumigation.