eBook Chapters

The current status of advances in fruit breeding is through the development of different scientific approaches augmented by ever-increasing knowledge and application of genetics, statistics and biotechnology. These innovative approaches very specific for a species in most of the cases, are the major tools of the fruit breeders to tackle the different objectives of fruit improvement programme at present Fruit improvement is a very slow process due to the long generation cycle varying from species to species, thereby reducing the chances of exploiting genetic recombination. Besides this factor, most of the fruit species are either highly heterozygous or polyploidy in nature. Due to this reason the asexual propagation of fruit plants is a conventional means while wide segregation occurs upon sexual reproduction. Such expectation is not unlikely because the types selected as commercial varieties are definitely to be vigorous ones, and a positive correlation exists between vigour and heterozygosity.

This discussion on breeding of fruit plants involves different aspect of the species concerned is so essential as well as fundamental that discussion of them must procede any consideration of breeding methods themselves. The plant species are grouped into two-self-pollinated and cross-pollinated. These two groups have emerged on the basis of pollination mechanism which plays significant role in the method of breeding application. To emphasize the difference in the reproductive systems of these two groups one should know the details about floral biology, mechanism of pollination control, reproduction by asexual and sexual means and self and cross-pollinated plants.

Transgenic crops, developed through genetic engineering techniques, have revolutionized modern agriculture by conferring novel traits that enhance yield, quality, and resilience. This chapter delves into the intricate interplay between the scientific advancements in breeding approaches for transgenic crops and the critical ethical concerns and regulatory frameworks that accompany them. The chapter begins by introducing the concept of transgenic crops and provides an overview of the diverse breeding techniques employed to manipulate plant genomes. These techniques include Agrobacterium mediated transformation, biolistic transformation, CRISPR-Cas9 (clustered regularly interspaced short palindromic repeats–associated protein 9) genome editing, RNA interference (RNAi), and site-specific integration methods. Each method is presented within the context of its potential benefits and limitations. The subsequent sections address the ethical considerations that arise from the creation and deployment of transgenic crops. The potential ecological and biodiversity impacts, cross-contamination risks with conventional crops, and issues related to patenting genetically modified organisms (GMOs) are explored. Furthermore, the chapter examines the ethical implications of genetically modified crops on human and animal health and questions surrounding the monopolization of seed resources. Looking to the future, the chapter outlines emerging breeding technologies and anticipates potential challenges in ethical consideration and regulation.

All hybrids and varieties perform better under conventional farming in response to excess use of chemical fertilizers and pesticides, which are harmful to humans, animals and environment. Hence, there is a need to develop varieties/hybrids exclusively for organic farming. Breeding aspects of organic farming include breeding tools/methods which are used to breed varieties/hybrids including testing and multiplication under organic conditions duly following the principles of organic farming as defined by IFOAM. These cultivars should have high nutrient use efficiency, resistance to diseases and pests, competitive ability against weeds, higher yield and stability across environments along with enhanced nutritional quality. This book chapter briefly discusses the aspects of breeding that are involved in generating cultivars suitable for organic farming.

1. Introduction

Currently, organic farmers rely heavily on conventionally developed and produced varieties. Nevertheless, in order to optimize their production under organic agriculture, it is necessary to develop cultivars that are more suitable for organic cultivation. According to some studies, the naturalness of organic agriculture should go beyond simply by avoiding chemical inputs and substituting natural and organic components during the transition from conventional to organic farming.

INTRODUCTION

The ultimate objective of forest tree breeding is to develop fast growing high yielding genetically improved superior strains in order to replace the wild natural forest stands so as to obtain higher forest productivity per unit area and time. A breeding programme, in fact, involves purposeful management of genetic variability present in a taxon. The variation is regulated through controlled mating. This obviously, needs detailed information on the nature and extent of genetic variation on one hand and equally on the reproductive biology of the species. A clear understanding of phenological behaviour, time of anthesis, time and duration of stigma receptivity, fertilization, mode of pollination, seed development etc. is necessary for attempting crosses between genetically different forms which is invariably involved in the breeding programmes. Although, tree breeding work has been done to a great extent on the temperate species (Devey et al. 2002; Murat et al. 2006; Gotzenberger et al. 2007), no serious efforts were made in the past on tropical forest species including Jatropha (Jatropha curcas), presumably due to the consideration that similar breeding methods may perhaps, be applied to the tropical trees as well. This, however, is not applicable, as the phenological and reproductive features are typical different to each species. It was in this background that the present research article was planned to collect information on floral biology, breeding behaviour and hybridization programme in Jatropha for subsequent application in its genetic improvement.

Crops plants are broadly classified into two groups based on their mode of reproduction viz. sexually propagated and asexually propagated. In sexually propagated crops seeds are the primary propagules and it is produced by the fertilization of male and female gametes. Whereas, asexual reproduction or clonal reproduction covers all those modes of multiplication of plants where normal gamete formation and fertilization does not take place and vegetative propagules are the means of reproduction. Since sexual reproduction involves meiosis, segregation and recombination, the creation of variation is a continuous process which is inevitable in these crops. On the other hand, in asexual propagation progenies are identical to the parent clones and they are genetically similar without any variation and they reproduce via mitosis. The most important vegetatively propagated food crops are potato, sugar cane, cassava, sweet potato, yam, plantain/banana, and fruit trees. Other crops with asexual propagations are some ornamentals, grasses, and forages.

Expression of genetic potential for growth and yield of a crop variety is directly dependent upon the environment comprising both climate (weather) and soil components. As discussed in the preceding chapter, the term ‘salt-affected soils’ encompasses a broad group of adverse but distinct soil conditions, namely, saline, alkali (sodic) and acid soils with further variations such as coastal and inland locations as well as arid and water-logged situations (Swaminathan 1977; Bresler et al. 1982). Factors limiting growth and yield of crop plants in various categories of problem soils are different and specific. Likewise, adaptive strategies evolved by plants to cope with the prevailing edaphic stresses, such as salt stress, also vary a great deal as indicated in Table 1. It is not unexpected therefore, that even varieties within a crop often show notable differences regarding tolerance to adverse soil conditions (Epstein et al. 1980; Devine 1982; Shannon 1984; Sayed 1985). Hence, it is essential that the breeder must understand the inherent charaderistics of the problem soil with which he is concerned and should also simultaneously appreciate that basically it is the sensitivity of crop variety, rather than the soil parameters per se, that essentially determines the occurrence as well as the magnitude of actual soil problem (Rana 1977). Since the degree of tolerance (adaptation) of crop varieties to different kinds of salt affected soils is genetically controlled, it is axiomatic that it can be improved through genetic manipulations by adopting suitable breeding procedures.

Introduction

Stress is any unfavorable condition for a plant’s normal growth and development. In the case of crop plants, such adverse conditions are caused by biological (biotic) and non-biological (abiotic) environmental factors. Abiotic stress is the negative impact of non-living factors on living plants in a specific environment. Usually, abiotic stress is unavoidable, and we can only go for its management.

The most basic stresses include:

• Extreme (high/low) temperatures

• Soil-chemical properties

• Water deficiency

• Excessive moisture

• Element toxicity or deficiency

A. Salinity

Salinity is a predominant problem affecting crop productivity. Over 800 million hectares of land on earth are saline. This accounts for more than 6% of the total land mass on earth. Salinity is a global problem and is prevalent especially in the arid and semiarid regions, where leaching of salts is poor due to low rainfall or irrigation. Brine-affected soil occurs due to natural causes such as weathering and deposition of oceanic salts (eg. recently tsunami in India). In addition, human interference with the environment such as deforestation and/or desertification has resulted in the rising of water table, thus increasing the salt concentration in the root zone. This excess salinity poses a threat to sustainable crop production.

A plant is said to be healthy or normal when it carries out its physiological functions to the best of its genetic potential. These normal functions include division, differentiation, development, absorption of water and mineral from soil and translocation of these throughout the plants, photosynthesis and translocation of photosynthetic product to areas of utilization or storage, the metabolism of synthesized compounds, reproduction and storage of food supplies.

A plant becomes diseased when it is disturbed by pathogen under certain environmental conditions which interfere with one or more of its essential functions. Diseased plant refers to any disturbance brought about by living organism under environmental factors, which interfere with normal function of plant or in other words when any organ and part of plant is not doing their work properly and when either the growth or reproduction is not going forward in natural or regular manner.

Crop production is challenged by abiotic and biotic stresses results in low yield and high production costs.

Magnitude and intensity of stresses are increasing dramatically due to climate change causing recurrent droughts, increased temperature (heat) and emergence of new diseases and pests.

Diseases of plants are produced by a variety of organisms from plant and animal kingdoms viz., fungi, bacteria, viruses, nematodes and insects. The diseases reduce total biomass (dry matter) production and consequently yield of the crop by general stunting, damage to the leaf tissues, fruits and seeds or by killing the plants. The degree of damage would depend upon the intensity of infection but both need not be proportional. One serious effect of disease is the disappearance from cultivation of otherwise excellent but susceptible varieties.

Vegetable crops have been found to be highly susceptible to biotic stresses from the disease causing microorganisms and insects-pests. The ability of pathogen and insect-pests to attack and proliferate in the host plant is highly specific. There are wide differences in the host plants in response to the attack by pathogens and insects. Although control of the diseases and insects by the use of chemicals is possible to certain extent but indiscriminate use of fungicides or insecticides over the crop has several disadvantages. Besides increasing cost involved in chemical control, residual toxicity of the chemicals such as fungicides, antibiotics and insecticides in food chain and development of resistance against pathogens and insect-pests to different chemicals are serious problems.

Genetic improvement of host plants conferring resistance to diseases and insect-pests is considered to be the best approach in the management of diseases and insect-pests, and this is more particularly true in case of vegetable crops. Indiscriminate use of chemicals in the vegetable sector has led to health hazard. This has resulted in switching towards organic vegetables. However, cost of production of organic vegetables naturally will not permit the common people to consume these products. Therefore, the best option is to induce resistance in the host varieties. The resistant varieties could in turn be an important component in the organic vegetable farming, thereby reducing cost of production to certain extent.

In general, disease means an impairment of health or a condition of abnormal functioning. Plant disease is an abnormal deviation from the normal physiological functioning of the plants their by it causes quantitative and/or qualitative losses. Disease may caused by biotic agents (infectious) like fungi, bacteria, viruses, viroids, phytoplasma, spiroplasma, fastidious bacteria, protozoa, nematodes and parasitic higher plants or abiotic agents (non-infectious) like extreme environmental factors includes temperature, light, soil moisture, atmospheric humidity, environmental pollutants, carbon-dioxide concentration, soil nutrient deficiency, acid rain, soil pH and herbicides. 

Plant diseases, in spite of the various measures adopted to control them, continue to be a major cause of crop losses. At times these losses have been so heavy that they have caused severe famines. Diseases are caused by a wide variety of organisms such as fungi, bacteria, viruses, mycoplasma and nematodes. The diseases may be partially or completely controlled by chemical, cultural and genetic methods. When no single method is effective in controlling a disease, integrated control constituting a combination of the three methods of disease control (chemical, cultural, genetic) may be effective. If host resistance alone is sufficient to check a disease, then it is to be preferred to other methods because it is the least expensive, has no adverse environmental effects and involves no specific action on the part of the farmer, even when only partial, genetic resistance supplements chemical control and makes it more effective in comparison with chemical control on a completely susceptible cultivar.

Many plant diseases have been successfully controlled by exploiting genetic resistance especially where differentiation in the pathogen with respect to resistance genes in the host is lacking. In some cases, even when pathotype differentiation occurs in the pathogen, genetic resistance in combination with other methods has given adequate control. Breeding for resistance to highly variable air-borne fungal pathogens has claimed much time and effort of plant breeders and success has often been transient. The reasons for the shortlived success have become clear from research during the last quarter of a century.

This chapter starts quoting first para of the book entitled Disease Resistance in Plants by Van Der Plank (1968). “In 1958 the American Phytopathological Society met to celebrate its Golden Jubilee and review the problems and progress in plant pathology during the 50 years, 1908 to 1958. J. C. Walker was elected to review the problems and progress in controlling plant diseases by host resistance, a fitting tribute to one who perhaps more than any other had contributed during those 50 years both to understanding of nature of resistance and to the practical application of resistance to problems in horticulture and agriculture. In his summary Walker wrote “By and large the development of resistant varieties must be looked upon as a continuing program. The potential variability of most pathogens (including viruses) will not permit any currently successful variety to remain so for an indefinite period”. This opening para tells the importance of breeding for resistance to diseases in crop plants on a continuous basis as the fight between host and the pathogen will go on and on.

In practical agriculture, resistance represents the ability of a certain variety to produce larger crop of good quality than an ordinary variety at the same level of insect population. During the 19^th Century, the French wine industry survived a major set-back largely due to the use of resistant root stocks imported from America and which still maintain their resistance levels against the beetle pest (Painter, 1951). Another important example of resistant variety is the U-4 variety of cotton possessing high level of resistance to the jassid, Emposasca spp. (Parnell, 1925). The excessive use of pesticide on oilseed crops needs to be minimized owing to several reasons: (i) most of the pesticides are lipophilic and are likely to be carried in the oil (ii) in a few cases like Brassica, leaves and inflorescence are consumed as saag (pot herb), (iii) the oilseed crops provide the raw material for the vanaspati industry, cosmetics, etc., (iv) many of the oilseeds and oils are directly consumed without further processing, and (v) the oil cakes are used as cattle feed. Thus there is an urgent need to exploit the non-pesticidal methods of pest control, among which the use of resistant varieties assumes a great significance. The details of each oilseed crops are given below:

Crop varieties are domesticated since civilization, and their continued cultivation depends on continuous breeding programmes for insect, disease and other stress resistance. World wide, insects and their associated problems cause threat to crop production. Many crops suffer from insects, which may be in the form of direct damage by feeding or indirectly by the transmission of diseases by insects as vectors. Until now, chemical crop protection is seen as the major way to combat these problems. However, insects develop resistance to the insecticides very quickly. Apart from controlling pest insects, insecticides also affect beneficial insects, such as predators and parasitoids of the pest insect, pollinators, and harmless fauna, thus upsetting ecological balance results in many unwanted problems. Hence, the best strategy is to prevent the problems that occur. The most economical and environmental friendly way of controlling the insect pests of crops would be through host-plant resistance (HPR). Resistant plants help farmers to grow crops with minimal use of chemicals. This will lead to a reduction in the cost of production, thereby increasing the profit margin for farmers and thus importance of breeding for pest resistance is manifested.

Genetic resistance is the more efficient and the more environmentally friendly way to protect crops against phytonematodes. Nematode management is complex, hence, the prevention of an initial phytonematode infestation in pathogen-free areas is of fundamental importance. However, after the entry of the nematode into an area, it is virtually impossible to eradicate because it is a soil-dwelling organism. In this regard, the genetic resistance of plants to nematodes is considered one of the most efficient and economically feasible methods to prevent production losses (Matsuo et?al?, 2012). Thus, breeding for nematode resistance is essential in crop management to obtain a high yield and stable production.

The immediate and long-term objective of modern plant breeding in all countries irrespective of the state of their advancement is increasing the availability of food to meet the calorie-protein requirement of their people. In the past, breeders have concentrated their efforts on increasing the yield of the important crop species. Better adaptation to local environmental conditions, high production and better resistance to the major pests and diseases have been among the priority goals of genetic plant improvement. Yielding ability and stability undoubtedly deserve high priority but enough attention also needs to be paid to improving nutritional characteristics of the plant produce for their maximum utilisation. Awareness of nutritional requirements and the optimal characteristics of crop products to be utilised as food and feed, therefore, becomes an important parameter of breeding effort.

The main source of food in the developing world is cereals which provides 45 to 85 per cent of the total calories and 50 to 80 per cent of the total protein requirements. The consumption of animal proteins, which are nutritionally well balanced, is low and costly and beyond the reach of the low income groups. On the other hand, plant proteins are cheaper to produce and easier to store and transport. All these factors go in favour of increasing the quantity and quality of cereal proteins in order to improve the dietary and nutritional status of the masses in the developing world.

Proteins are made up of about twenty different amino acids. For man, eight of these amino acids, valine, methionine, leucine, isoleucine, threonine, phenylalanine, lysine and tryptophan, are essential (EAA) for constituting a well balanced diet. In impioving the grain quality of cereals consideration should, therefore, be given apart from the content of carbohydrates, fats, minerals and vitamins in the grains, to improving the protein content as also the amino acid composition of the protein.

When conditions in the plant growing environment are less than the optimum, the plants experience stress which is broadly termed as abiotic stress. Major abiotic stresses impacting crop yield significantly are as follows (Grover et al., 2004; Acquaah, 2007):

Drought: This is the environmental condition caused by lack of adequate rainfall. This is also termed as water stress or desiccation stress. Effects of drought on crop plants are complex and variable and are greatly accentuated by a number of interacting factors. The onset of drought in general has been observed to reduce germination, emergence, hypocotyl length, water uptake and the mobilization of dry matter reserves even at the early growth stages. Drought stress causes a marked reduction in leaf area. Soil moisture availability at the seed germination, anthesis and at post-anthesis growth stages determines as to what extent production potential of crops would be expected in drought-prone situations.

The yield losses in field crops may be attributed to inadequate water availability at the critical growth stages. Crops therefore differ in their susceptibility of growth stages to water stress. Stress exposed plants immediately lower down relative water content (RWC) of their leaves, leaf water potential, osmotic potential. Turgor pressure may also be decreased unless plants have finally adapted to drought by opening of stomata again and improving the water potential. It has been reported that low leaf expansion rate at the early stage and accelerated leaf senescence accompanied by mortality of older leaves at later stage decreases total leaf green area.

29.1 Introduction

An environmental factor that interferes with the complete expression of genotypic potential of a crop is called stress. The stresses may be biotic (pathogens, insect-pests, etc.) or abiotic. The main abiotic stresses are drought, mineral deficiency/toxicity and heat or cold. The losses due to abiotic stresses can be minimized by:

Crop management: The degree of stress can be reduced by suitable agronomic/soil management practices, e.g., irrigation to relieve drought stress, soil amendments to reduce salinity.

Development of resistant cultivars: This offers the cheapest, easiest to apply and most eco-friendly approach to reduce losses due to any stress.

Indirect breeding: Evaluation of materials under stress often helps in identification of a resistant line that may become an important commercial cultivar.

???????Direct breeding: It is deliberate breeding of materials for stress resistance. When a genetically variable material is grown under the stress environment, selection can be based on survival, yield and other traits contributing to stress resistance.

Plant abiotic stresses are external and nonliving factors that have harmful effects on plants. A non-living factor must exert influence on the normal range of environmental variation to adversely and significantly affect the plant performance or the physiology of the organism. Abiotic stresses are the most harmful factors affecting the growth and productivity of crops worldwide, resulting in a yield reduction ranging from 10% to 100%. They are most harmful when occurring together with other abiotic stresses and their effect in yield will only worsen with the climatic changes experienced now and expected to be more severe in the future.

28.1 Introduction

The stress that is caused by biological agents or factors such as diseases, insect-pests and parasitic weeds is called biotic stress. The term disease can be broken into two words: “dis” (means negative, reverse or opposite) and “ease” (means comfort, or freedom from pain or discomfort). Hence, plant disease can be defined as any harmful alteration from the normal functioning of physiological processes. Diseases may be bacterial, fungal or viral. A wide range of insects infests various crop plants. The extent of damage caused to crop plants by various organisms is usually in the order fungi > bacteria > viruses > nematodes = insects. But the relative importance of these organisms varies to a great deal in different crops. Breeding of cultivars resistant to diseases and/or insect-pests is the cheapest, safest and most dependable means of limiting the losses due to them. Resistant cultivars form an important component of integrated management of diseases and insect-pests.

28.2 Breeding for Resistance to Biotic Stresses-Diseases

Agrios (1970) has defined disease as: “Disease is a series of invisible and visible responses of plant cells and tissues to a pathogenic microorganism or an environmental factor that result in adverse changes in form, function or integrity of plant and may lead to partial impairment or death of the plant or its parts.” The organism causing disease is called pathogen, while the plant affected by the disease is called host.

The principles underlying breeding for resistance to diseases are much the same as for other characters, except for one important difference, i.e., the diseases caused by pathogens are the product of interaction between two genetic systems, that of the host and that of the parasite. Both systems are capable of variation and evolution and affect the interaction between host and pathogen. Here the breeder is required to deal with the heritable traits of both the host plant and the pathogens invading it.

Biotic stresses include diseases and insect pests which cause serious damage to the crop plants and ultimately yield loss. Biotic stresses can be listed as follows:

• Diseases caused by pathogens which include fungi, bacteria, and viruses
• Insects
• Nematodes
• Parasitic weeds

Another category of stresses are called as abiotic stresses which are caused by environmental factors as:

• Water stresses (water logging, drought)

Introduction

Worldwide damage due to insect pest attack accounts for 15 per cent crop losses, despite the use of insecticides which represents over US $100 billion (Krattiger, 1997). The annual cost of insect control itself amounts to US $8 billion, thus warranting immediate and economical control measures. The crop varieties developed in the past 30 years were high yielders, but unfortunately had poor storage characteristics and were highly susceptible to pest damage. Insect-pests are capable of evolving to biotypes that can adapt to new situations, for instance they overcome the effect of toxic materials or bypass natural or artificial plant resistance, which further confounds the problem (Roush and McKenzie, 1987). Under these circumstances, provision of food to the rapidly expanding population has always been a challenge facing mankind. This problem is more acute in the tropics and sub-tropics, where the climate provides a highly conducive environment for a wide range of insects and necessitates massive efforts to suppress the population densities of different pests in order to achieve an adequate supply of food. In developing countries, the problem of competition from insect-pests is further complicated with a rapid annual increase in human population (2.5-3.0 percentage) against a meager 1.0 per cent increase in food production. In order to feed the ever expanding population, crop protection plays a vital and integral role in the present day agricultural production to minimize yield losses. Currently, the crop protection practice in agricultural systems relies exclusively on the use of agrochemicals, although a few specific cases do exist, where inherent varietal resistance and biological control have been successfully employed. The exclusive use of chemical pesticides not only results in rapid build-up of resistance to such compounds, but their non-selectivity affects the balance between pests and natural predators, and is generally in favour of pests (Metcalf, 1986).

Introduction

Within the very small portion of the plant kingdom that includes the world’s crop plants, the legumes are a large group second to the cereals as sources of human food. Legumes belong to the family leguminosae with a group of bacteria, Rhizobium, which is able to utilize atmospheric nitrogen. This symbiosis which occurs in the root hairs may be the key to the success of legumes worldwide distribution. The family leguminosae includes about 18,000 species, characterized by their fruits, which are pods, by their (usually) alternate, pinnate or trifoliate leaves (Cobley and Steele, 1976). The diversity in the family ranges from hardwood trees of the tropical rain forests to the herbs of temperate pastures.

Vegetables are considered protective foods and play an important role in human nutrition. These help to combat malnutrition and also diversify diets with variety of colours. The compounds imparting various colors to the vegetables are important antioxidants that also help to combat degenerative diseases like cancer. Over the years, vegetable sector has made an appreciable progress in terms of production and productivity and emerged as the better option to diversify agriculture, generate employment and enhance farmers’ incomes. The worldwide production of vegetables has doubled over the past quarter century and the value of global trade in vegetables now exceeds that of cereals.

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.

Horticulture, which includes fruits and vegetables, plantation crops, spices, flowers, and medicinal and aromatic plants, has proved beyond doubt its potentiality for gainful diversification. One of the significant developments is that, horticulture has moved from rural confine to commercial production. Recently horticulture has emerged as one of the best option of diversification for effective land use planning and to achieve inclusive growth. The achievement in the development of horticulture through crop improvement is laudable, as the sector now contributes more than 30 percent to GDP of agriculture and has maintained the growth rate of more than 5 percent during the last two decades.

Breeding objectives genetic resources and techniques for breeding

• There are countries that consume 100 to 150 kg yearly per capita while others which do not even make it to 10kg.
• Genetic variability is the raw material of the plant breeder.
• International network for the improvement of Banana and Plantain (1 NIBAP), Prance to conserve the available germplasm.
• Only pathogen gene-free planting material can be used for construction or distribution from the gene bank for further multiplication or utilization in any breeding program.
• Fruit breeders have therefore tended to utilize single gene variants in performance to polygenic variation.
• In general, for most commercial requirements, homozygous is inadequate by six or seven generations of selling (56 or 37).
• In the dominance hypothesis, it is assumed that the deleterious gene is normally recessive.
• The simplest approach for the selection of our breeders is mass selection.

Indian jujube (Ber) belongs to the genus Zizyphus and family Rhamnaceae having more than 600 species. The family includes trees with spine, shrubs and climbers. The original home of Ber is Myanmar and India. Many workers have tried to classify it on the basis of leaf, flowers and fruits characteristics. Some tried to divide into two groups i.e. having smooth leaves on both surfaces and having leaves downy beneath. Ber as a tree has been described it as small, much branched or a large shrub with dense spreading habit, bark dark gray, branches elongated, leaves with glabrous shining upper surface densely covered beneath with whitish hairy growth.

Ber has attracted sustained breeding attention owing to its wide adaptability, good quality and nutritive value. However, problems like poor shelf life, incidence of powdery mildew disease, fruit fly and fruit borer have hindered the extension of the area under this crop. In Chinese jujube, the problem of fruit cracking and ‘witches broom’ disease are the major hindrances in its cultivation. There are two major cultivated species viz., Ziziphus mauritiana and Ziziphus jujuba, which are widely distributed covering vast regions in Asia. The wild population found is heterozygous and extremely variable. As a result, many local selections were made, some of which have become widely recognized as cultivars. The success of any breeding programme depends on the extent of genetic variability in the source population. The assessment of variability is therefore a basic requirement of breeding programme. Since most of the plant characters of economic importance are governed by the group of genes and are highly influenced by environmental variation, it is difficult to judge whether the observed variability is heritable or due to environment. This necessitates optimizing of phenotypic variation into its heritable and non heritable components, so that the selection of parents

5.1. Characteristics of asexually propagated crops

Majority of them are perennials

Many of them show reduced flowering and seed set.

Invariably cross pollinated.

Mostly polyploids.

Many species are inter specific hybrids.

4.1. Synthetic varieties

Produced by crossing in all combinations, a number of lines that combine well with each other.

The genetic organization of cross pollinated crops are different from that of self pollinated crops, because of differences in the reproductive system. Open pollinated populations are heterozygous with free inter mating individuals, heterozygous at most of the loci. Heterozygosity is an essential feature of commercial varieties of out breeders. It is maintained during breeding or is restored at the end. Population improvement involves selection, generation after generation, with recombination of selected individuals. Its aim to increase the frequency of favorable alleles in the population. The improved forms may be used for commercial cultivation or as a base germplasm for the derivation of inbred lines. The list of cross pollinated plants is presented in Table 10.1. The factors that promote the cross pollination are dicliny, dichogamy, herkogamy, self-incompatibility and male sterility. The breeding methods which are commonly used in cross-pollinated crops are population improvement, hybrid and synthetic varieties.

Population Improvement

In cross pollinated crops heterozygosity must be restored in the end product of any breeding programme. It is classified into the following types:

3.1. Selection

To isolate desirable plant types from a population.

3.1.1 Progeny test

Evaluation of growth of plants on the basis of performance of their progenies

Real value of plant could be known by studying the progeny.

The prime object of plant breeder is to develop high yielding variety with superior characteristics. Selection is based on the phenotypes of the plants. Consequently the effectiveness of selection primarily depends on the degree to which the phenotype of plants reflects their genotype. These are all self fertilizing species. In these species development of seed take place by self fertilization. Hence self pollinated species are also known as autogamous species. Various plant characters such as homogamy, cleistogamy, chasmogamy, bisexuality etc. promotes self pollination. The self pollinated crops with their description are given in Table 9.1. The breeding methods used in self and often-self pollinated crops are discussed below:

Plant Introduction

Plant introduction consists of taking a genotype or a group of genotypes of plants into a new area or region or environment, where they have not being grown earlier. It is very simplest and fastest method of developing new variety. It is of two types:

Reproduction that does not involve the union of male and female gametes is known as asexual reproduction. Reproduction in which sexual organs or related structures take part but fertilization does not occur, or crops which are propagated asexually or by vegetative means are known as asexually propagated crops. Most of the fruit plants are propagated asexually which consist of large number of clones. Example: sugarcane, potato, sweet potato, banana, mango, citrus, pears, peaches, litchi, crops that propagates by asexual means. The procedure of selection used for asexually propagated crops is known as clonal selection, since the selected plants are used to produce new clones or superior clones can be isolated from local variety, introduced variety or inter crossed population.

Important breeding methods can be classified as follows:
    1.    Introduction
    2.    Selection
    a.    Mass selection: Done in self pollinated crops, cross pollinated crops and dioecious crops.
    b.    Individual plant selection: Done in self pollinated crops, cross pollinated crops (line breeding) without control of pollination, artificially self pollinated lines, dioecious plants and clonally propagated lines.
    3.    Hybridization
    a.    Crossing in self pollinated crops.
    b.    Single crosses, double crosses and synthesized varieties.
    c.    Varietal crosses.

4.1. Flower and flowering in pigeonpea

Growth habit: Primarily, there are two major growth types in pigeonpea. These are determinate and non-determinate. The determinate growth in the pigeonpea plants is characterized by flowers in bunches at the top of the canopy (Fig 17a). In this case the epical growing points are transformed in to reproductive buds and bunches of flowers appear on the top of the canopy. Such cultivars are not popular as the management of insects such as Helicoverpa and Maruca becomes very difficult. Most of the cultivated types belong to another growth category called as non-determinate. In such genotypes the apical growing points remain vegetative and the plants keep growing under favorable conditions and it results in tall canopy with many spreading or compact branches. The inflorescence in this case emerges from the axil of secondary and tertiary branches (Fig 17b); and hang sideways. These types show less susceptibility to insects due to non-clustering nature of flowers.

17.1 Introduction

Almond or badam is a high energy nut. Almond kernels contain lipids (52.2%), protein (20%), carbohydrate (20.4%) and water-soluble sugars (4.4%). Irrigation affects almond yield and quality. Almond quality is primarily genotype dependent. Maturity at harvest can also influence kernel quality.

Aonla has been regarded as a sacred tree in India. The tree is worshipped as mother earth and is believed to nurture humankind because the fruits are very nourishing. It is also known as Amrit phal. Aonla is mainly recognized due to its high nutritive, medicinal and therapeutic properties. It contains high amount of vitamin C (500-1500 mg/100 g), it is also rich in pectin, iron, calcium and phosphorous. Dried fruits of aonla can be is used in curing hemorrhage, diarrhea, chronic dysentery, diabetes, jaundice, dyspepsia, cough etc. Recently, aonla has gained more popularity in arid and semi-arid region of the country because of its hardy nature, prolific bearing capacity and ability to grow under various adversities as a remunerative crop (Shukla et al.2002). It may be an important fruit in future due to its high productivity, suitability in wasteland particularly salt affected soil and sandy soil of arid ecosystem. Aonla is the main ingredient of Chavanprash and Triphala powder which is used for curing different abnormalities. The fruit contains a chemical substance gallic acid and leucoanthocyanin which have antioxidant property.

12.1 Introduction

Aonla (also called Amla, Indian gooseberry) is a tropical and sub-tropical fruit. It is mainly recognized due to its high nutritive, medicinal and therapeutic properties. It contains high amount of vitamin C (500-1500 mg/100 g); it is also rich in pectin, iron, calcium and phosphorus. Dried fruits of aonla are used in curing haemorrhage, diarrhoea, chronic dysentery, diabetes, jaundice, dyspepsia, cough etc. Aonla is the main ingredient of Chavanprash and Triphala powder. The fruit contains gallic acid and leucoanthocyanin which have antioxidant property. Its cultivation is more common and widely grown in Uttar Pradesh, Gujarat, Rajasthan, Madhya Pradesh and Tamil Nadu.

14.1 Introduction

Apple is the most widely grown temperate fruit of the world. It is considered as King of temperate fruits. It is rich in carbohydrate, calcium, phosphorous, iron, potassium, vitamin B6 . Apple is rich in antioxidant, flavonoids and dietary fibre. It is recommended to reduce the incidence of dental caries. The phytonutrients and antioxidants may help reduce the risk of developing cancers, hypertensions, diabetes and heart disease. Apple is mainly used for table purpose. The various processed products are prepared from fruit, e.g., juice, jelly, preserve, canned slice, wine, concentrated juice, cider and powder. It is widely cultivated in Afghanistan, Armenia, Azerbaijan, Bhutan, China, India, Indonesia, Iraq, Iran, Israel, Japan, Jordan etc.

20.1 Introduction

Arecanut (or betel palm) is chewed as narcotic either alone or more commonly along with betel leaf. Its nut has medicinal and pharmaceutical properties. About 1/10th of world population has a habit of betel chewing. Nut contains polyphenol (11-18 %) which includes flavonols like catechin, epicatechin, leucocyanidin, fat (9-15%), polysaccharides (17-25%), fibre and protein (6- 7.5%) and some minerals like calcium, phosphorous and iron.

Banana is one of the oldest fruits and second largest growing fruit crop in the world. It is also known as the Adam’s Fig and Apple of Paradise. Unlike other fruits banana is an herbaceous fruit plant. Banana breeding started in Trinidad, West Indies in 1922 and in Jamaica in 1924 (Shepherd, 1994). The driving force for this breeding programme was to develop improved Fusarium wilt (Fusarium oxysporum F. sp. Cubense) resistant banana for export trade (Buddenhagen, 1990). In 1960 both the programmes were combined under the Jamaica Banana Board. United Fruit Company also started a small breeding programme in Panama in 1920s. In India hybridization work was started at Central Banana Research Station, Aduthurai, Tamil Nadu in 1949. Important banana growing states are Maharashtra, Karnataka, Kerala, Tamil Nadu, Andhra Pradesh, Orissa, Bihar, West Bengal and Assam. Now a days in some districts of Uttar Pradesh, Harichal cultivar of banana is cultivated at commercial scale. In South India banana is extensively used in all auspicious occasions such as wedding, festival and worship. Banana is a good table fruit, besides, the cultivar Nendran is used for cooking, it is also used for preparation of halwa, sweet and chips etc. Main bud or heart of banana bunches is also used as vegetable in India, Thailand, Philippines, Malaysia and Indonesia. Musa textiles is known for strong fibre quality.

4.1 Introduction

Banana (Musa spp.) is one of the oldest fruits and second largest growing fruit crop in the world. It is also known as Adam’s Fig and Apple of Paradise. Important banana growing states are Maharashtra, Karnataka, Kerala, Tamil Nadu, Andhra Pradesh, Odisha, Bihar, West Bengal and Assam. In South India, banana is extensively used in all auspicious occasions such as wedding, festival and worship. Banana is a good table fruit. The cultivar Nendran is used for cooking; it is also used for preparation of halwa, sweet, chips etc. Main bud or heart of banana bunches is also used as vegetable in India, Thailand, Philippines, Malaysia and Indonesia. Musa textiles is known for strong fibre quality. Ripe banana contains about 20% sugar (but no starch) and about 4.7% protein. Further, it contains vitamins A, B, C, D and E and minerals such as K, P, Ca and Fe.

Ber (chinese date, chinese fig or bore) is an important minor fruit of India. It is hardy fruit tree cultivated all over India and also known as poor man’s fruit. It is most widely cultivated in Punjab, Haryana, Rajasthan, Uttar Pardesh, Madhya Pradesh, Bihar, Gujarat, Maharashtra etc. Ber can do well even under marginal growing conditions and provides quality yields at low cost (Shukla, 1996). Fruits are mostly eaten fresh but the other forms, such as dried, candied, squash etc can also be prepared from ber. Stem bark, root and leaves have some medicinal values. Leaves of ber are used as fodder in dry regions. Ber tree (Ziziphus xylopyrus) is a host plant for rearing the Tachardia laccad a lac insect (Sharma and Kore, 1990).

11.1 Introduction

Ber (also called Indian Jujube, Indian Plum, Chinese Apple and Masau) is an important minor fruit of India. It is most widely cultivated in Punjab, Haryana, Rajasthan, Uttar Pradesh, Madhya Pradesh, Bihar, Gujarat, Maharashtra etc. Fruits are mostly eaten fresh but other forms, such as dried, candied, squash etc. can be prepared from ber. Stem, bark, root and leaves have some medicinal values. Leaves of ber are used as fodder in dry regions.

Cashewnut is an important delicious and dollar earning cash crop of India. This crop was remained neglected due to its poor yield potential and prolonged harvesting season. Cashew was introduced mostly for soil conservation purposes. In the beginning of the 20^th century cashew kernels gained importance in the international trade as edible nut and the crop began to be considered as having commercial value. Cashew is commercially grown for its kernels although cashewnut shell liquid (CNSL) and apples are also valuable by - products. It is considered to be the most important edible nut in the world trade (Ascenso, 1986). India is the largest producer and exporter of cashewnut in the world. Cashew kernel is the rich source of protein, carbohydrate, unsaturated fats and minerals like calcium, phosphorus and iron. Cashew proteins are complete with all essential amino acids. Fats of cashewnut are considered as complete, attractive, easily digestible and non fattening, it can be used by both olds and infants. The cashew apple juice is rich in vitamin C and it has some medicinal properties.

21.1 Introduction

Cashewnut or cashew is an export-oriented crop grown for its nuts, a true drupe. It is often referred to as ‘wonder nut’. It is highly delicious and nutritive. Its nutritional composition compares well with almond, hazelnut and walnut. The economic part is kernel which is a unique combination of fats (47%), protein (21%), carbohydrates, minerals and vitamins. Nutritionally it is equivalent to milk, egg and meat, it is good appetizer, an excellent nerve tonic, stimulant, body builder. India is the largest producer, processor and exporter; and second largest consumer in the world. Cashew is grown in Kerala, Karnataka, Goa and Maharashtra along the west coast and in Tamil Nadu, Andhra Pradesh, Odisha and West Bengal along the east coast.

Citrus constitutes a major group of fruits comprising of mandarins, oranges, lemon, pummelo, grape fruits, tangelo, trifoliate orange, citron, citranges etc. Despite of inter-specific and inter-generic hybrids, Poncirus and Fortunella also belong to genus Citrus. During its long history, citrus has given the world numerous varieties both by open pollination, bud sports and of recently by controlled pollination and artificial induction of bud variation. Citrus fruit cultivation lies between latitude 40 0N also 40 0S where conditions are neither cold nor moist and dry. India is considered to be the home of several citrus species and they are found growing wild in some parts of the country. Many types of citrus still remain unexploited by man and such types are considered as semi wild. The productivity of citrus plant in our country is very low which is 7.65 tonnes/ha as acompared to Spain, Italy and Japan where it lies between 17-35 tonnes/ha. Sweet oranges cover an area of 42.4 thousand ha with an annual production of 510.8 thousand tonnes (Ghosh, 1985).