eChapters

Introduction

Plants are often subjected to unfavorable environmental conditions – abiotic factors, causing abiotic stresses - that play a major role in determining productivity of crop yields but also the differential distribution of the plants species across different types of environment. Some examples of abiotic stresses that a plant may face include decreased water availability, extreme temperatures (heating or freezing), decreased availability of soil nutrients and/or excess of toxic ions, excess of light and increased hardiness of drying soil that hamper roots growth. The ability of plants to adapt and/or acclimate to different environments is directly or indirectly related with the plasticity and resilience of photosynthesis, in combination with other processes, determining plant growth and development, namely reproduction. A remarkable feature of plant adaptation to abiotic stresses is the activation of multiple responses involving complex gene interactions and crosstalk with many molecular pathways.

Introduction

According to FAO estimates, about 50% total geographical area in India is under various degraded hazards and about 2.1 million ha of land is getting degraded and deforested annually (Sehgal et al., 1998). Out of that underground water in arid and semi-arid areas is saline or sodic in nature. While spices, medicinal and aromatic plants may be a boon for these areas, which not only withstand under adverse conditions but also could be productive and helps in mitigating these problems. However, other crops are remain less or unproductive in these areas.

Introduction

Under arid and semi-arid regions of the world, major problems are salinity, alkalinity and calcareousness, which seems to further aggravate with changing climate scenario. Besides, most of the developing countries lies in this zone with flanging population resulting from shrinking of land resource and good quality of irrigation water. Globally area under saline/sodic soils is about 953mha covering 8% of the land surface. Resent estimates indicate that 6.7 mha area in India is affected by soil salinity and alkalinity and about 25% of ground water are sodic and/or saline in the country. There are two important approaches for utilizing saline alkali or calcareous environment. The first one is to modify the environment so as to suit the plant or modifying the plant and the second one is to substitute the plant species so as to suit the environment. However, second option is cost effective and most sustainable.

Introduction

The hot arid region of the country is spread over nearly 31.7 million hectare land area in different states. The major part of hot arid region of the country lies in western Rajasthan (19.62mha) followed by North-western Gujarat (2.16mha). The major natural constraints in arid vegetable production comprise of very low and variable rainfall (100-450mm), very high potential evapo-transpiration rate, intense solar radiation (320-619/cm²/day), high wind velocity (20km/hr), high infiltration (9cm/hr), extremes of temperature (0 to 48^ºC), low relative humidity, high soil salinity, very deep ground water, etc. These bio-physical constraints reduce the productivity of cucurbits many fold. Despite  several constraints, the hot arid areas of western Rajasthan offers very good opportunity for cultivation of cucurbits like, watermelon, muskmelon, longmelon, bottle gourd, ridge gourd, tinda, summer squash, cucumber, etc.

Introduction

The hot arid zones of the country are spread over 32 million ha in the state of Rajasthan (61%), Gujarat (20%), Andhra Pradesh (7%), Punjab (5%), Haryana (4%), Karnataka (3%) and Maharashtra (0.4%), in addition to the cold deserts in the states of Jammu and Kashmir and Himachal Pradesh which are characterized by hostile agro-climate and fragile eco-system. In Rajasthan, the hot arid zone covers 12 district of whole western Rajasthan. It covers the 61 % area of the Rajasthan State and characterized by an annual rainfall between 100 – 500 mm with a coefficient of variation (CV) varying from 40 – 70 per cent; low and erratic rainfall combined with extremes of temperature (450-500 cal/cm2/day); low relative humidity; high potential evapo-transpiration value ranging from 1600 mm in eastern part and 1800 mm in western part of the region.

Continuous vegetable cultivation year round in the limited available land, without adopting crop rotation practices induces stress, which leads to low vegetable crop productivity. These conditions apart from building up soil-borne pathogens will also lead to other deleterious factors such as temperature extremes, flooding, drought, salinity, heavy metal contamination, insufficient nutrient uptake, soil pH stress, etc. causing severe crop loss. To overcome these abiotic stress conditions, grafting is an environmentally friendly technique for reducing losses in production in solanaceous and cucurbitaceous vegetable crops. The cultivated area of grafted Solanaceae and Cucurbitaceae has increased tremendously in recent years because the objective of grafting has been greatly expanded (Lee et al., 2010) to reduce infections by soil-borne pathogens and to enhance the tolerance against abiotic stresses.

Introduction

In-spite of environmental, bio-physical and resource constraints in most parts of Rajasthan, the state can be classified into three distinct agro-climatic zones namely hot arid, semi-arid and sub-humid  from horticultural perspective. These diverse zones have excellent vegetable production potential with wide range of crops, varied opportunities and resource utilization. The extremes of high (March–October) and low (December–January) temperature conditions together with associated abiotic stresses in the hot arid and semi-arid regions limit the choice of crops and their genotypes, quality of produce and productivity. Vegetable exploitation with adaptive and native crop-plant species is generally found to be potential and stable under arid to semi-arid agro-climatic conditions of the state that receive 150–650 mm of rainfall and having abiotic stresses due to climatic variations, drought, frost, hot and cold winds, soil and water quality.

Rajasthan is the largest state covering about 34.2 million hectare geographical area of the country, of which 27.1 million ha (79 %) is under arid and semi-arid sub-tropic hot climate and spread over 21 districts. The land-scape of Aravali range provides boundary for arid western, semi-arid eastern and sub-humid to humid areas of the state. In-spite of several environmental restrictions and bio-physical constraints in most of the parts, the state can be classified into three distinct agro-climatic region i.e. hot arid, semi-arid and sum-humid from horticultural perspective. On the basis of research experiences and SWOT analysis over last two decades for R&D road-map of Rajasthan Horticulture, the classified zones have excellent vegetable development potential with wide and varied opportunities of crops and utilization of resources.

Introduction

Date palm (Phoenix dactylifera L., Family: Palmaceae) also known as Khajoor, Kharek is an ancient important fruit tree of semi-arid and arid regions of the world. It grows well under poor desertic soils due to its hardy plant characteristics and deep root system. It is also one of the most suitable fruit trees to grow under saline irrigation conditions. It is well known fact that date palm has its feet in the water and its head in sun. It requires dry hot climate for growth, development and maturity of fruits. In arid region, crop production is a risky preposition where date palm cultivation contributes in achieving food security, high nutritive value food, crop diversification, desertification control, income generation and foreign exchange earnings. It can be grown at such places where adequate irrigation facility is available besides dry hot climatic conditions (Chandra et al., 1992; Singh and Dhandar, 2007).

Introduction

High population pressure has forced us to plough 46% of our country area for food production. The present productivity of 12.36 tones/ha of fruits needs to be raised to 40.0 tones/ha by using N, P₂O₅, K₂O with other inputs, since recommended ratio is 0.75:0.50:1.00. To achieve this target, the present day requirement of 0.67 million tones N, 0.46 million tones P₂O₅ and 0.91 million tones K₂O has been raised to 1.07, 0.58 and 1.14 million tones, respectively in order to supply the recommended ratio of fertilizers to an area of 3.65 million ha growing fruits (Yadav, 1999). Similarly in vegetables, the present production level of 13.41 tones/ha to be raised to 40 tones/ha requires 1.25 million tones of N, P₂O₅ and K₂O combined at the ratio of 1.33: 0.88 and 1.00.

Introduction

Canopy management is the manipulation of tree canopies to optimize the production of quality fruits. The canopy management, particularly its components like tree training and pruning, affects the quantity of sunlight intercepted by trees, as tree shape determines the presentation of leaf area to incoming radiation. An ideal training strategy centers around the arrangement of plant parts, especially, to develop a better plant architecture that optimizes the utilization of sunlight and promotes productivity. Light is critical to growth and development of trees and their fruits.

Introduction

Today, increasing attention is focused upon the impact farming practices, are having on the environment and there is an increasing emphasis on more sustainable methods of crop production. Systems need to be adopted that are more sensitive to environmental issues, genetic diversity, wildlife and their habitats and in some cases the social structures of rural communities. Furthermore, consumers around the world are more sophisticated and critical than in the past, demanding to know how and what has been used to produce their agriculturally derived products. These issues can be taken up as three main challenges: 1) to improve food security, rural livelihoods and income; 2) to satisfy the increasing and diversified demands for safe food and other products; and, 3) to conserve and protect natural resources. Several scientific advancements have been made in the field of agriculture to address these challenges.

Introduction

The term cropping system refers to cropping patterns used on a farm and their interactions with farm resources, other farm enterprises, and available technology over a fixed period. The fruit based cropping system includes different fruit crops as major component on particular field for a fixed period through intercropping or multistory cropping. Intercropping is growing of two or more crops together on same piece of land simultaneously with definite row arrangements to utilize farm resources efficiently. Multistory/Multitier cropping refers to growing together of  crops of different heights at the same time on the same piece of land and thereby using land, water and space in an efficient and economic manner.

Land, a non-renewable resource, is central to all primary production systems. Over the years, the country’s landmass has suffered from different types of degradations. Land degradation can be defined as lowering of land productivity due to the deterioration of land’s physical, chemical and biological condition. Physical land degradation is due to water erosion, wind erosion, compaction, crusting and water logging and chemical degradation is due to the processes of salinization, alkalization, acidification and nutrient depletion. Biological degradation is due to the reduction of soil biota and organic matter, degradation of vegetation and impairment of activities of microflora and fauna. Land degradation is steadily increasing due to the growing pressure on land and unsustainable land use. Land degradation and the associated loss of soil productivity and quality is of great concern both from food production and environmental conservation point of view. An ever-increasing population created enormous pressure on land resources.

Introduction

Soil test-based fertility management is an effective tool for increasing productivity of agricultural soils that have a high degree of spatial variability. However, major constraints impede wide scale adoption of soil testing in most developing countries. In India, these include the prevalence of small holding systems of farming as well as lack of infrastructural facilities for extensive soil testing (Sen et al., 2008). Under this context, GIS-based soil fertility mapping has appeared as a promising alternative.

Introduction

The climatic elements such as solar radiation, temperature, precipitation, humidity, evaporation, evapotranspiration and wind velocity affect growth and development of saplings. These climatic factors are not favourable for successful propagation of various horticultural crops in arid region. The main climatic features of Indian hot arid agro-ecosystem is high wind speed, sand storm and high temperature during summers up to 48-50oC  and during winter season temperature falls to the 2-3^°C, low atmospheric humidity i.e. 20-30% during maximum period of the year. Moreover the relative humidity goes down to below 10 per cent during summer months.

Introduction

Origin of Water Bodies and Hot Arid Regions (Thar Desert) 

The origin of the hot arid regions (Thar Desert) is a controversial subject. Some consider it to be 4000 to 10,000 years old, whereas others state that aridity started in this region much earlier. Another theory states that area turned to hot arid zones (desert) relatively recently: perhaps around 2000 - 1500 BC. Around this time the Ghaggar-Hakra ceased to be a major river. It now terminates in the desert but at one time was a water source for the Indus Valley Civilization centre of Mohenjodaro. It has been observed through remote sensing techniques that Late Quaternary climatic changes and neotectonics have played a significant role in modifying the drainage courses in this part and a large number of palaeochannels exist.

Introduction

Water is the driver of life/ liquid of lift or elixir of life for flora and fauna. It plays an important role in plant as it constitutes about 35-95% part of plant. Water is a mode of transportation of nutrients from roots to shoots and vice-versa, a thermal regulator of temperature inside the plants, source of hydrogen for the reaction of CO₂ for photosynthesis and is essential for maintaining turgidity and servility of plants. Water is required for agriculture as well as for other sectors (domestic, industries, etc) and the demand of water is increasing alarmingly.  Presently agriculture consumes over 80 per cent of total water consumption in India. The country is endowed with many perennial and seasonal rivers. The river, low ever 71 per cent of water resources is concentrated in 36 % of the geographical at area. Water resource of India, population in per capita water ability and estimates of water needs are given below.

Land and water resources are central to agriculture and rural development, and are intrinsically linked to global challenges of food insecurity, land degradation , poverty, climate change adaptation and mitigation that affect the livelihoods of millions of rural people across the world. Current projections indicate that world population will increase from present figure of 6.9 billion to 9.1 billion in 2050. As a result, the world food demand will increase. Since, both land and water resources, the basis of our food production, are finite and already under heavy stress, so future agricultural production will need to be more productive and more sustainable at the same time. The largest contribution to increases in agricultural output will most likely come from intensification of production on existing agricultural land. This will require widespread adoption of sustainable land management practices, and more efficient use of irrigation water through enhanced flexibility, reliability and timing of irrigation water delivery. The prevailing patterns of agricultural production needs to be critically reviewed.

The hot arid regions are spread over about 31.7 million ha area mainly in the States of Rajasthan, Gujarat, Andhra Pradesh, Punjab and Haryana, which inhabit on an average 61 persons per square km making up a population of nearly 20 million people. The Indian arid zone is characterized by high temperature and low and variable precipitation which limit the scope for high horticultural productivity. However, these conditions greatly favour development of high quality production of fruits such as date palm, ber, pomegranate, citrus, aonla, bael, grapes, guava and in vegetables such as cucurbitaceous crops, spices and some medicinal plants. The optimized technologies and inputs could increase the existing low productivity. It is now realized that there is a limited scope for quantum jump in fruit and vegetable production in the traditional production areas. The amelioration of the extreme conditions is also considered vital for life support to the inhabitants of this area.

Introduction

The arid region of India, constituting 12 m ha area  which occurs dominantly in the northwestern part of the country. The state of Rajasthan accounts for highest area (61%) followed by Gujarat (19.6%) Punjab (5%) and Haryana (4%) of the total geographical area of hot arid ecosystem. These areas experience an annual rainfall between 100-500 mm with the coefficient of variation 40-70 per cent. The mean annual rainfall in the western Rajasthan varies from less than 100mm in extreme western part of the Jaisalmer district to more than 400 mm in eastern part of the region. The high temperature during summers as high as 48^ºC and low in winters up to –3^ºC. High wind velocity  (10-13 km /hr) and high annual  evapo- transpiration  (1527 mm /year)  again gives a great threatening to the arable cropping in this region. The vagaries of monsoon in terms of its occurrence and distribution during the season has a wide variability >48 per cent with 30-35 days of average rainy days per year.

A key question facing agricultural scientists in the 21^st century is how to produce sufficient amounts of food, feed and farm income while protecting and improving environmental quality (Robertson and Swinton, 2005). Intensive soil tillage, mismanagement of land, water and fertilizers had severe negative economic, environmental and social consequences (Foley et al., 2011; Godfray and Garnett, 2014; Tilman et al., 2011). Presently depletion and / or degradation of natural resources (land, water, and biodiversity), decreasing farm profitability, low input use efficiency (fertilizer, water, energy, pesticides, and labor), environmental pollution (soil, water, air), climate change and scarcity of farm labour are threatening the sustainability of crop production systems.

Introduction

Agricultural research and development in the past 50 years has primarily focused on increasing productivity through intensification of input use to  maximize grower income and  minimize hunger and food shortage (Andow et al., 2009). The full environmental costs of this policy such as water and soil pollution, soil and resources impoverishment (Tegtmeier & Duffy, 2004), only recently became apparent, and this awareness has led to the beginning of a change in philosophy away from purely production-oriented practices towards those that are more environmentally sustainable (Alexanian, Metera, & Schuler, 2009). In addition, agriculture and its interactions with the natural environment have begun to emerge more strongly in political, economic and social agendas reflecting the increasing importance of sustainability to consumers. Consumers are now demanding food that are of high quality, locally produced, regionally specialized, organic, fairly traded, and are humanly and ethically produced. Achieving all or some of these goals with fewer resources is now the objective of modern sustainable agriculture (Mason, 2003).

The Indian arid zone is characterized by high temperature, low and erratic rainfall which limits the scope for high crop productivity. However, these conditions greatly favour the development of improved quality in a number of fruits such as date palm, ber, aonla, bael, pomegranate, kinnow, lasoda and in vegetables such as cucurbits, legumes and solanaceous crops, spices, flowers, medicinal and aromatic plants. The existing low productivity could be increased by following improved new technologies and inputs. It is now realized that there is a limited scope for quantum jump in fruit and vegetable production in the traditional production areas.

Abstract

Forestry in India is very important for its wood, fuel and many non-wood products which were being used from ancient times by our forefathers for different personal and commercial use. Farmers face lots of problem in forestry because of its long gestation period, dependence on nature, bulkiness of outputs, season oriented production, perishable in nature, lack of processing centres for value addition at farm and intermediate levels, price fluctuation of forestry products, forced sale/distress sale of tree growers, low wage rate to workers in forestry activities and farmers in sufficient knowledge on market information. Establishment of institutional setup to promote forestry is urgent in the recent times.

Abstract

Intellectual property has increasingly assumed a vital role that we are witnessing today with the rapid pace of technological, scientific and medical innovation. Moreover, changes in the global economic environment have influenced the development of business models where intellectual property is a central element establishing value and potential growth. In India several new legislations for the protection of intellectual property rights (IPRs) have been passed to meet the international obligations under the WTO Agreement on Trade-Related Aspects of Intellectual Property Rights (TRIPS). Forest seed of economic importance and the non-timber forest products (NTFPs) play a very important role in the country’s economy.

Abstract

Forests are the second largest land use after agriculture in India covers around 24% of the geographical area. The key tree species like Teak, Sal, Shisham etc are commonly used for timber purposes however the species like Eucalypts, Acacias, Poplar, Melia and Leucaena are mainly used under agroforestry system in India. The most of the genetic material (seed/planting stock material) used in forestry sector in India is obtained from unspecified sources, from stands, natural or planted, which are neither classified nor managed specifically for seed or planting stock material production.

Abstract

People dealing with forest tree seeds are very much concern with the collection and supply of pure and quality seed. Assessing genetic purity of tree seed is always a challenge. Besides, studying tree diversity and tree improvement are also the key components of forestry. With the discovery of DNA based molecular markers these tasks have been made easier and authentic. So, the basic concepts behind different molecular markers were the principal concerns of this chapter. It has been focused here about the pros and cons of the markers along with their applicability. The application may be expanded towards hybrid seed testing and even to clonal forestry.

Abstract

The forest cover has declined at an estimated rate of 3-3.5% per annum due to huge deforestation in many countries during last decades. Being the prime necessity for forest regeneration, importance of quality seed management and its handling procedures have been genuinely recognized for greater interest of the environmental stability throughout the world. Growing of new trees and forests would play a major role to save the future world particularly under the present scenario of climatic change and this implies an increased demand of quality forest reproductive materials.

Abstract

In afforestation and reforestation programs, seed has become a valuable commodity and its collection, identification, handling, processing, testing, storage and certification requires prudent planning. The research and development in seed science and technology have made significant progress in recent years. The quality of seed has been the subject of increasing interest among Forest Managers and the Scientists. Not every seed is suitable for sowing. Sometimes, the seeds do not develop into normal plants or the plants produced do not produce the expected harvest. This manuscript reviews, the progress made to-date in the forest tree seed germination and highlights future line of action.

Abstract

Seed is the most important input component for productive forestry. Large quantities of quality seed are needed every year to raise the nursery stock for propagating the desired plant species.  Commercially important species like Dalbergia sissoo, Eucalyptus tereticornis, Pinus roxburghii and Populus deltoides have become more important. Superior genetic qualities of seed have profound positive impact on growth rates and productivity of plantations and quality of the produce. To save and multiply the entire lot of valuable forest plants it is very essential to preserve and multiply those plants for which special type of nurseries are to be established. There is necessity to have special techniques and methods to meet the demand of seed and only hi-tech nurseries can satisfy this type of demand.

Abstract

Insect pests, fungi, bacteria and other injuries are found in all types of environment and affect the growth, production and survival of both plants and animal species in one way or other. Similarly a large number of insects belonging to different orders, families and genera feed on pods and seeds in natural/ during storage and cause injuries. Regeneration failure in several broad leaved and conifers in India and other countries by heavy insect attack in the natural stands at the time of inflorescence and seed formation and on the ground after seed shedding causes heavy loss to number of afforestation programmes. Several methods like chemical, cultural, natural and biological are available for reduction in loss caused to seeds by insects. Generally, earlier the control measure, the smaller the destruction. Forest seeds can be stored safely by taking some precautions before their final storage, viz. inspection of the seeds for their moisture content, visual examination of cleaning method, scanning through soft X-ray technique, thermotherapy or treatments with chemicals, etc. The present chapter has covered review regarding damage caused to seeds by different insect pests and their management options.

Abstract

On average 13 million hectares of the world’s forests disappear every year due to different reasons. Among them forest diseases is one of the prominent factor. Seeds of soft wood and hardwood trees are attacked by fungi and other microbes.  Seed-borne pathogens of wood trees affect nursery seedlings and reduce seed germination and seedling vigor. The micro-organisms that are mostly associated with tree seeds are fungi, bacteria and to a lesser extent viruses. There are many mechanisms by which tree seeds acquire pathogens. Indeed, both the occurrence and severity of many seed-borne fungi, is often traced to the mishandling of fruits, cones or seeds. The majority of pathogens associated with forest tree seeds are fungi, producing only or predominantly the asexual (anamorph) stage (Deuteromycetes).

Abstract

The drive of planting trees is increasing because the values of trees and forest are being appreciated in all over the world. In most of the countries good quality tree seed is not readily available for a number of reasons especially in forestry sector. Though providing the best conditions for crop growth and health is the foundation of seed quality, the factors that can have the most important effect on seed viability and vigor are harvesting, extraction, cleaning, transportation, and storage because it is easy for seed to become damaged at any of these stages. Ex situ conservation through long-term storage of seed is possible for a significant proportion of higher plants. Long-term seed storage serves as a safe and relatively inexpensive method of plant genetic resources conservation.

Abstract

The availability of the quality seed is the first and the most important requirement which is of great relevance in tree improvement programme. Unlike agriculture, the forestry seeds have great variation in size, shape, dormancy, viability, moisture content, etc. It needs special techniques for collection, handling, processing and storage of the seeds of the large number of forest species. A strong commitment to improving tree seed technology is required for full utilization of seed supplies with the help of recent advances in seed physiology. Substantial improvements have occurred as a result of seed technology research offering the potential for major advances in traditional seed production and distribution systems.

Abstract

Although  people have harvested seeds and fruit from trees for centuries, only after World War II, the science and theories of forest genetics begin to be seriously applied to and practiced in operational forestry around the world. The genetic improvements, or gains, need to be captured, packaged, and mass produced so that these gains could be deployed in operational forestry systems. This can be accomplished through seed orchards which is a link between tree breeding and silvicultural activities. Seed orchards are by far the most frequently used sexually reproducing forestry production populations in the world. Apart from the genetic improvement, seed orchards are also used for the production of seed that is well adapted to specific environments. Seed orchards can be categorized according to the generation of breeding or the type of plant material used.

Abstract
Better seed production technology is vital to furnish quality seed of improved varieties. Trees are generally propagated from seeds and the suitability and quality of the seeds have a big effect on the success of the plantations, afforestation and reforestation programmes raised from them. It must be stressed that good seed implies seed which is both of high viability and vigour and is genetically well suited to the site and to the purpose for which it is planted. The use of sound seed from stands of high inherent quality is widely recognized as the best means of ensuring fast-grown and healthy plantations capable of yielding high quality wood. Quantity, as well as quality, of seed production is important. Seed quality depends on factors like source, time and techniques of harvest, processing and storage practices. Unlike agriculture, the forestry seeds have great variation in size, shape, dormancy, viability, moisture content, etc.

Abstract

Knowledge of  seed biology is crucial for proper management of  seed sources as well as the handling of seeds. In broadest sense seed technology includes the development of superior crop plant varieties, their evaluation and release, seed production, seed processing, seed storage, seed testing, seed certification, seed quality  control, seed marketing and distribution and research on various aspects. Vegetative propagation has also become popular for the propagation of some tree species, but seed propagation remains the principal mode of propagation in both the temperate and the tropical region. Forest plantations are a powerful tool in the continuing efforts of foresters to increase productivity per unit area apart from mitigating the climate change and global warming issues. Hence to improve the existing stock in terms of yield, quality, disease resistant and desired traits, seed technology can play a major role in providing quality genetic material.

Okra/Ladies finger/Bhindi
1. Leaf blight/Spot
Pathogen
Cercospora abelmoschi Ell. & Ev.
Symptoms
The fungus grows as shooty to dark olivaceous, ectoparasite covering entire leaf lamina. Pathogen initiates as small isolated fungal growth on lower side of leaf but very soon it spreads on both sides. Pathogen reduces severely the photosynthesis area. Infected leaves fall down very quickly after dropping and rolling. It causes severe loss in seed production crop as well as in the late sown crops.

1. Damping off
Pathogen
Pythium spp
Phytophthora spp
Fusarium spp
Sclerotium spp
Symptoms
It is a term used to describe the damage caused by various fungi to the seed and emerging seedling in the reduced plant stand and sometimes it is so serious that  resowing becomes inevitable. Major symptoms are the failure of the seedlings decay or sudden death of the emerged seedlings roots and lower stems of emerged seedlings become soft and watery and may be reddish brown in colour.

Cauliflower, Cabbage and Knol khol
1. Leaf spot
Pathogen
Alternaria brassicae (Berk.) Sacc.
Symptoms
Alternaria leaf spot usually appear in early stage in cauliflower while at later stage symptoms in cabbage appear as circular light brown spot in leaves. Concentric rings are clearly visible on the spots. In older plants on leaves, petioles and stem, brown to black circular to slightly elongated spots appear.

Tomato
1. Damping off
Pathogen
Pythium aphanidermatum
Fusarium spp.
Sclerotium spp.
Symptoms
Damping off is the most important disease of tomato. Several seed and soil borne fungi can kill before the tender redical and plumule establish in the nursery bed. The pre emergence damping off and seed rotting is the usual cause of poor seedling stand. This type of damping off causes hidden loss but the post emergence damping off is more serious problem. Seedlings get infected near the soil line (collar region) after emergence and give wire stem symptoms. The tissue become soft, water soaked and weak causing the seedlings fall over and later on they die. The entire action is so fast that leaves remain green but they are unable to stand further.

Vegetables
Peas
1. Rust
Pathogen
Uromyces fabae (Pers.) de Bary
Symptoms 
The fungus produces characteristics rust pustules on the host. Pustules are mostly found on the leaf blade, though often they may be found on the petiole and stem of pea plants. The sori are small, roundish, open, and powdery as well as brown coloured. In severe infections, the leaf may wither, resulting in considerable damage to the crop. As the plants near maturity, the fungus produces the telial stage on the host.

1. Damping-off
Pathogen
Pythium aphanidermatum (Edson.) Fitz.
P. debaryanum                  
Rhizoctonia solani Kuhn.
Fusarium spp.
Sclerotium spp.
Symptoms
Damping-off of onion seedlings occurs in two stages:
    (i)    Pre emergence
(ii)    Post emergence
In pre emergence stage, plumules are killed before they reach the soil surface. They may be infected, killed even before the hypocotyls have broken the seed coat.

Microbial inoculants in agriculture, horticulture and forestry can be defined as preparations containing strains of microorganisms which can augment the microbiological process such as nitrogen fixation, phosphate mobilization, excretion of growth promoting substances, decomposition of organic wastes, biocontrol of insect pests and diseases etc. Thus they become an important component of sustainable agriculture. Microbial inoculants are based on renewable sources available in soil and nature and are low cost input and eco-friendly. These inoculants carrying the microorganisms when applied to soil/plant promote plant growth and productivity.

Sustainable agriculture or organic farming wherein biological inputs are maximum and chemical inputs are minimal, is drawing the attention of farmers across the world including India. For replacing chemical fertilizers, which supply plant nutrients by organic manure, the basic requirement is the availability of raw material i.e. the organic matter or biomass that can be decomposed to organic manure. The question that is often asked is what are the different sources of available biomass and how much of it is available? Different sources of biomass can be categorized as

Herbicides are the chemical substances used to kill weeds, i.e., unwanted plants that compete with crop plants for soil nutrients. Chemical herbicides are the most effective immediate solution to most weed problems. Use of chemicals, however, can be harmful to wildlife, to the environment and to humans. Chemicals are also expensive, and weeds develop resistance to the chemicals. For these reasons, there is now a move toward alternative methods of controlling the weeds. One of the most promising is biological weed control, which involves using one living organism to control the activities of another organism.

The adoption of modern agricultural technologies has culminated into serious problems of pesticide resistance in major pests, resurgence in minor pests, elimination of populations of natural parasites, predators and pollinators, environmental pollution, pesticide residues in food chain and health hazards. World Health Organization (WHO) estimates one million pesticides poisoning cases and 20,000 deaths every year globally. This is due to high pesticide residues in food chain including cereals, pulses, vegetables, fruits, milk and milk products (including mother’s milk), fishes, poultry, meat products and water. Twenty five per cent of Indian food products contain pesticide residues above tolerance level compared to only 1.2% globally.

Emphasis of present day agriculture is to produce more with lesser land, water and man power. Apart from natural calamities like drought, flood etc., biotic stresses like pests, diseases and weeds also influence the crop productivity greatly. Sixty to eighty per cent of the total crop losses are attributed to the devastations caused by pests and diseases. Farmer’s income in recent years is decreasing gradually due to increased cost of inputs particularly in plant protection. The excessive dependence on chemical pesticides leads to the development of resistance in insect pests and pathogens, out breaks of secondary pests and pathogens / biotypes and occurrence of residues in food chain. To avoid this situation the concept of Integrated Pest Management (IPM)/ Integrated Disease Management (IDM) approach should be considered on top priority.

The rhizosphere is the narrow zone of soil surrounding the root that is under the immediate influence of the root system. This zone is rich in nutrients when compared with the bulk soil, due to the accumulation of a variety of organic compounds released from roots by exudation, secretion and deposition. Organic compounds released by plant roots include amino acids, fatty acids, nucleotides, organic acids, phenolics, plant growth regulators, putrescine, sterols, sugars and vitamins. Because these organic compounds can be used as carbon and energy source by microorganisms, microbial growth and activity is particularly intense in the rhizosphere.