eChapters

Definitions
 
    •    Toxicology: Knowledge (or science) of poisons, including their chemical properties, identification, biological effects, and the treatment of conditions they cause.

    •    Poison: Any solid, liquid, or gas that, when introduced into or applied to the body, can interfere with the life processes of cells of the organism - by its own inherent chemical properties - without acting mechanically and regardless of temperature.

    •    Poison = Toxicant: The term poison is now used less often. Reason: Historical application of the term (malicious) vs. a compound used as a feed additive, agricultural, or other chemical - manufactured to fulfill a perceived human need.

We may study the nutrient metabolism in a better way as explained in the following summarized form in Table 1.

Historical Development of Soil Science/Agriculture

Francis Bacon (1561-1624 A.D.): Found the water as nutrient of plants.

Van Helmont (1577-1644): Give the ideas about the role of soil as a simple source of water and minerals for the plants.

Section-A : Write True / False

Q.1 The moment generating function (m.g.f) of a random variable X (about origin having the probability function f (x) is defned as

Abstract

Rural women play a vital role in farming system operations and contribute substantially in the physical aspect of farming, livestock management, postharvest and allied activities. Around 43% of the agricultural labour force of developing countries is composed of women dependency. India has achieved self sufficiency in agricultural production, but a considerable amount of production gets spoiled in every year due to inadequate post-harvest management, processing, infrastructure and skill. To uplift the livelihood and economic conditions of the rural women there is an urgent need to impart trainings for skill development regarding the value addition of horticultural crops. This offers tremendous opportunities for women occupation but also inculcate entrepreneurial characteristics in them. Trainings and skill development are useful for rural women as they can add more value to the seasonal fruits and vegetables and generate varieties of products namely Pickle, Murabbaa, Chutney, Jam, Sharbat etc. These efforts enhance their family income by around 30-40 thousands per annum as they fetch more prices of raw produce after processing. Moreover during peak production times glut only promote produce and profit loss. Instead of direct marketing of their produce they can do value addition of their produce and then sell them in market, it not only increases the value of their products but the prices also enhance by many folds. After giving training to rural women, they are motivated to go for self marketing of their produce at domestic and village level. Similar way these trainings can transform the life style and income level of farming families comprehensively.

Introduction 
Augmented energy demand as well as impacts of employment of fossil coals on human health and environment, stresses and imposes the need to lessen the use of conventional fuels or replace them. Equally, global warming has stretched to a distressing level due to many diverse anthropogenic actions leading to increased pollution. The alternate energy sources are desirable that might be the conspicuous and sustainable approach of enabling environmental remediation, besides meeting the global energy call (Grosser et al 2016, Kanchanasutha et al 2016). A potential solution is generation of Biofuels, either conventional biofuels produced from agricultural crops or advanced biofuels produced from wastes, inedible crops or forestry products (Sreedevi Sarsan et al 2021). Advanced biofuels production especially by the utilization of agricultural and animal wastes using new technologies and processes are gaining increased interest among researchers and general public all over the world. Food waste, municipal trash, animal waste and other wastes can all be utilised as feedstocks to create biogas, a clean and sustainable energy source and thus may be the ideal replacement for traditional energy sources. The raw biomass may be converted into fuel products like biogas by briquetting, gasification, and anaerobic digestion, among other processes (Deepanraj et al 2015). In comparison to landfills, incinerations, and composting processes, anaerobic digestion (AD) is suggested as an inexpensive and environmentally benign technique for the generation of renewable energy (Van Forest et al 2012; Nishio et al 2007; Capson-Tojo et al 2016; Xu, F et al 2018; Cha, M et al 2020). The production of energy-rich biogas and alleviation of issues related to the removal of organic waste are all achieved by anaerobic digestion (AD) of organic solids (Sonakya et al 2001). This is since AD is a highly energy-efficient and ecologically benign technique. In an atmosphere devoid of oxygen, the AD system uses anaerobic microbes to transform the naturally occurring substances in the biomass into biogas. The primary byproduct of AD, biogas, has a methane content of roughly 50-70% by volume and 30- 40% atmospheric carbon dioxide (CO2) when feedstocks are digested under anaerobic circumstances, with small levels of hydrogen sulphide (H2S) (0.1-3% v/v), humidity, and other trace pollutants also present (Sahota et al. 2018). The generation of biogas is known to be influenced by factors such as waste types, pretreatment procedures, the microorganisms or enzymes added, operation circumstances and design of the digestors (Mao et al 2015).

Introduction

Spectral signature: A spectral signature is the unique pattern of reflection and emission of a target at different wavelengths. This difference helps to classify remote sensing images based on the spectral signatures of different objects.

Electromagnetic (EM) spectrum: The EM spectrum is the range of all types of EM radiation. Some examples are visible light from a lamp, radio waves from a radio station, microwaves, infrared light, ultraviolet light, X-rays, and gamma rays.

Spectral response patterns: A spectral response pattern is the amount of energy that an object reflects or emits at different wavelengths. It shows how the object interacts with the EM radiation.

Generation system of seed multiplication is nothing but the production of a particular class of seed from specific class of seed up to certified seed stage. The choice of a proper seed multiplication model is the key to further success of a seed programme. This basically depends upon,

• The rate of genetic deterioration
• Seed multiplication ratio
• Total seed demand (Seed replacement rate)

ABSTRACT

Of the total production of the crop yield, only 63 per cent is available for human consumption. The remaining is lost in more or less equal proportions to weeds, pests and diseases. Prior to genetic engineering, the exchange of DNA material was possible only between individual organisms of the same species. In the field of agriculture for instance, farmers have continuously modified naturally occurring species through seed selection and controlled breeding. With the advent of the recombinant DNA technology, it has however been possible to identify specific genes associated with desirable traits in one organism and transfer those genes within and beyond the boundaries of species into other organisms.

1. Genes for herbicide resistance

Modern agriculture has developed a range of effective herbicides to tackle the effects of weeds on crop yield. Some of the most useful of these are broad-spectrum herbicides because they are active against a wide range of weeds. However, these can only be used at times when the crop is not itself vulnerable to herbicide action. The development of herbicide-resistant crops therefore offers the opportunity to spray crops at the most effective time to kill weed species without damaging the crop plants. By definition, herbicides are much more toxic to plants than to animals. Therefore, it is not surprising that they generally affect ‘plant-specific’ biological processes. The herbicidal activity of many herbicides has been found to result from the specific inhibition of a single enzyme/protein. The following are four distinct strategies for engineering herbicide resistance: i. Overexpression of the target protein, ii. Mutation of the target protein, iii. Detoxification of the herbicide, using a single gene from a foreign source and iv. Enhanced plant detoxification.

Random Mating

Random mating occurs when each female gamete has an equal chance of being fertilized by any male gamete of the same plant or with any other plant of the population and, furthermore, there is an equal chance for seed production. It is not possible to achieve true random mating in plant breeding because selection is involved. Consequently, it is more realistic to describe the system of mating as random mating with selection. Whereas true random mating does not change gene frequencies, existing variability in the population or genetic correlation between close relatives, random mating with selection changes gene frequencies and the mean of the population, with little or no effect on homozygosity, population variance, or genetic correlation between close relatives in a large population.

Acid soils are found in India in about 93 million hectares ( Table 1) and they occur in the Himalayan region, the great Indo-Gangetic and Brahmaputra plains, peninsular plateau and uplands and the coastal plains including island eco-systems under varying environmental conditions of landscape, geology, climate and vegetation. Conditions which are conducive for the formation of acid soils, such as high rainfall coupled with high temperature encouraging intense weathering and loss of alkali and alkaline earth metals with a simultaneous accumulation of iron and aluminium hydroxy compounds or the formation of free acidic substances in the humid forest foot hill regions, exist in some region or other in almost all the states in India.  A soil with pH less than 7.0 is deemed as an acid soil (Soil Survey Staff,1951). However, for characterization and classification, acid soils may be defined as those having pH less than 5.5 in 1:1 water extract (Soil Survey Staff, 1999).

Horticulture deals with the art, science, business and technology of cultivation and management of horticultural plants. The word Horticulture is derived from two Latin words viz. ‘Hortus’ (means garden) and ‘Culture’ (means growing). Horticulture is an aesthetic science that deals with cultivation of fruit, vegetable, spice, plantation, medicinal, aromatic and flower crops. There is a vast therapeutic use of horticulture wherein gardening and aroma therapy are used to deal with new age maladies like depression and various addictions.

In ancient times, huge gardening spaces to grow large number of fruits, vegetables and flowers were available and these areas were demarcated with the help of high walls. This enclosed area was referred to as garden. This led to the term garden culture. The land area is decreasing due to industrialization and population growth, at the same time, there is a drastic increase in demand for horticultural produce. To meet the increased demand for horticultural produce and to cope up with the space constraints, multitier cropping systems, vertical gardening and other intensive cultivation practices are being resorted to. Hence, horticulture may also be described as the “Practice of growing and manipulating plants in a relatively intensive manner”.

Presently, fruits, vegetables, flowers and ornamentals are grown not only within the home premises, but also in large quantities on a commercial scale. In other words, many horticultural crops throughout the world are grown primarily as business enterprises. Thus, horticulture has two aspects in general i.e., the amateur and the professional. In addition, with the establishment of horticultural experiment stations as an integral part of colleges and universities, comparatively a large amount of scientific information on the behaviour and cultivation of horticultural plants and products is freely available. This information or literature, constitutes the science of horticulture, and the application of this scientific information constitutes the “Technology of Horticulture.” Thus, present day horticulture may be defined as the science and technology of production, processing and merchandising of fruits, vegetables, flowers and ornamentals where each crop has its own science and technology. Consequently, horticulture may appear differently to different people. To a teacher, professor, research scientist, extension official and landscape architect, it is an applied science and a profession, while to a commercial producer, wholesaler, a retailer of horticultural products, or to the manufacturers or seller of horticultural products, it is a business. It is also a fascinating hobby for connoisscur.

The narrow sense heritability estimates were high for days to first flowering, plant height at first flowering, number of leaves at first flowering, plant height at maturity, productive tillers per plant, boot leaf area, 100 grain weight, grain length and grain L/B ratio. These characters may be controlled by additive genetic variance. This indicated that the individual genotype can be evaluated readily from their phenotypic expression. Simple selection would more effective in the sets of materials exhibiting greater additive genetic variability and desirable mean performance. Thus, it merit selection in the next generation. On the other hand, the remaining traits may largely be controlled by non-additive genetic variance or the number of genes controlling these traits may be more, or these traits may largely be influenced by a large number of modifiers or might be largely influenced by environment. As the effects of the environmental variance were generally low, the observed low heritability for the above traits might be due other factors other than environment. These traits are hard to improve by selection. It necessitates progeny testing.

The relative magnitude of different gene effects and an understanding of the mode of inheritance of complex quantitative traits have a direct bearing on the method of hybridization and selection which should be adopted in a specific breeding programme. Useful biometrical methods have been developed by the Birmingham group of scientists, to analyse the genetic architecture in organisms, through the use of first and second degree statistics obtainable from the true breeding inbreds, their first generation crosses and the different types of segregating progenies (Mather, 1949; Hayman, 1958; Gamble, 1962; Mather and Jinks, 1971). Since then this method has been widely used in the genetic analysis of various crops.

Generation of new genetic variability through recombination breeding followed by appropriate selection procedure is one of the key factor for crop improvement. Gain in selection is restricted by correlated response of agronomically desirable as well as undesirable characters. There is a host of examples in various crop species where genes for desirable agronomic traits have been found to be closely linked with those governing undesirable characters (Murthy, 1971; Clegg et al., 1972). Such close linkages delay the realization of the full recombination potential in many crops. The biparental mating or the disruptive mating scheme, finds its importance in the improvement of autgamous speice,s because it increases the probabilities of obtaining useful recombinants as compared to selection without intermating (Hanson, 1959; Jensen, 1970).

In contrast to classical pedigree breeding, random mating population could produce large amounts of variability. This variability can be maintained in the population by the use of recurrent intermating, while the population is improved by selection. According to the standard breeding methodology in self-pollinated crops selection for quantitative characters are generally taken up in early segregating generations. For characters like yield, selection is continued till the material becomes homozygous. Such characters are controlled by large number of genes and a very large population has to be raised to make selection effective. Since most plant breeders could never grow the theoretically required size of population, the recombination is highly restricted. It is likely that many of the valuable genes may be practically lost in the process of advancing the material by continued selfing the generations. Andrus (1963) suggested crossing of selected sibs in early generation for reassembling the genes capable of functioning in a balanced polygenic system.

Eswaran (2007) made genetic analysis of six parents and their 30 hybrids of Okra with the method of analysis proposed by Hayman (1954b). He estimated the various genetic parameters viz., _D?, _F?, H?₁, H?² and Ê as well as the various genetic ratio. The results are presented in Tables 69 and 70.

The estimates of _D? were significant for seven out of ten characters studied. This indicated that the component of variation due to additive genetic variance was important for days to seedling emergence, number of first fruiting node, height of first fruiting node, plant height, days to first picking, number of fruits per plant and fruit weight. These characters could be improved by resorting to simple selection. The estimates of H? ₁and H? ₂were positive and significant for almost all the characters studied. It indicated that there were unequal frequency of alleles i.e., u ¹ v at all the loci, in this context, ‘u’ refers to the frequency of alleles which increase the mean expression of the character and are situated at loci which exhibited dominance. On the other hand, ‘v’ corresponds to the frequency of alleles at loci that decreases the expression of the character. Further proof for the unequal distribution of the alleles over loci was obtained

Among the different biometrical methods available, triple test cross analysis is one of the most efficient designs currently available for investigating the genetic structure of populations. It provides a test of epistasis and in its absence it gives independent and equally precise estimates of additive and dominance genetic components (Mather and Jinks, 1982).

11.1. Statistical analysis

Triple test cross

Jinks and Perkins (1970) method was applied to detect epistasis and estimate additive and dominance components of genetic variance.

Abstract

Genetic analysis of yield and yield components in tomato (Lycopersicon esculentum Mill.) was worked out by using half diallel mating design. The good general combiners observed were Solan Vajr, FT-5 and UHF-265 for plant height; UHF-107 and UHF-260 for days to first picking; Solan Vajr for number of fruits per cluster; FT-5, EC-191536 and UHF-120 for average fruit weight; Solan Vajr, UHF-265 and FT-5 for harvest duration and FT-5 and Solan Vajr for marketable yield per plant. The best three specific combiners for marketable yield per plant were EC-191536 x Solan Vajr, BL-342-1 x FT-5 and UHF-107 x EC-191536. Hayman’s approach revealed non-allelic interaction in the expression of number of fruits per cluster, number of fruits per plant and marketable yield per plant. Preponderance of non-additive gene action was observed with dominance towards tallness, delayed first picking, more fruits per cluster, longer harvest duration and higher marketable yield, while involvement of complimentary epistasis was indicated in the inheritance of average fruit weight and number of fruits per plant.

Introduction
Aquaculture, the farming of aquatic life like fish and shellfish, has become essential for global food supply. It helps meet the rising demand for seafood, supports countless livelihoods, and promotes sustainable development. As wild fish populations dwindle due to overfishing and environmental damage, aquaculture provides a sustainable way to ensure food security and economic growth. Monosex culture, the practice of raising only one sex of a species, is particularly useful for fish like tilapia and prawns, where one sex grows faster and more efficiently. By focusing on single-sex populations, aquaculture can boost production, simplify management, and increase overall yield. Monosex culture is important because it can improve profits while protecting the environment
Historical Development of Monosex Practices
The development of the monosex culture began in the mid-20th century when scientists started to investigate ways to control the sex ratios of fish populations. Early methods focused on selective breeding to improve traits like growth rate and size. Over time, advancements in genetic manipulation and hormonal treatments have revolutionized the field, allowing for more precise control over sex determination. Hormonal treatments like 17 alpha methyltestosterone for sex reversal in tilapia during the 1970s, significantly improved production efficiency. The development of genetic technologies, such as chromosome manipulation and CRISPR, has further propelled monosex culture into mainstream aquaculture practices. Today, monosex culture is recognized as a cornerstone of sustainable aquaculture, with ongoing research aimed at refining techniques and addressing ethical considerations associated with genetic interventions.

In genetic studies it is necessary to distinguish two causes of correlation is chefly pleiotropy, though linkage is a cause of transient correlation, particularly in populations derived from crosses between divergent strains. Pleiotropy is simply the property of a gene whereby it affects two or more characters, so that if the gene is segregating it causes simultaneous variation in the characters is affects. For example, genes that increase growth rate increase both stature and weight, so that they tend to cause correlation between these two characters. The degree of correlation arising from pleiotropy expresses the extent to which two characters are influenced by the same genes. But the correlation resulting from pleiotropy is the overall, or net, effect of all the segregating genes that affect both characters. Some genes may increase both characters, while others increase one and reduce the other the former tend to cause a positive correlation the latter a negative one. So pleiotropy does not necessarily cause a detectable correlation. The correlation resulting from environmental causes is the overall effect of all the environmental factors that vary; some may tend to cause a positive correlation, others a negative one.
Genetic correlation
Hazel (1943) introduced this statistic and is defined as the correlation between the additive genetic values of two traits. When two traits are considered together we have three population parameters:

ABSTRACT

Though the genetic control of sex determination is being explored in several animal systems, no much information is available on the genetic basis for sex specificities in dioecious or sexually polymorphic plant species. Date palm is a unique member of the family Palmaceae which exhibits dioecy. Here we report the sex-specific variation in the genomic DNA of male and female date palms as revealed from an extensive study conducted with palms representing different date palm growing regions of the Kingdom of Saudi Arabia. The genomic DNA content in females was less than 60 per cent compared to those of the male genotypes. Polymerase chain reactions carried out to amplify different segments of the alcohol dehydrogenase (AdhA) gene from the date palm genomic DNA yielded two DNA fragments each in the female genotypes where as the same primers amplified a single fragment in male plants. Genomic Southern analysis of Eco R1 restriction digests showed RFLP between the male and female genotypes with the male plants showing a single hybridization signal of approximately 14 kb size and the females showing six additional bands of varying molecular weights. The results of our investigations reveal the potential of molecular biology in differentiating the sex in date palm at DNA level. Further research is needed to develop DNA markers that will help to unequivocally identify the sex of dioecious plants at the seedling stage.

Plant breeding is essentially a technology. Any technology will stand the test of time if it is based on sound concepts. In the case of plant breeding, the concepts are provided by the science of genetics.

Plant productivity in its broad sense requires consideration of not only yield but also of a number of its direct and indirect components. For example in groundnut, besides pod yield, shelling percentage, 100-kernel weight and oil content are components relevant to defining productivity. A number of physiological (like biomass, leaf area, specific leaf weight), morphological (like days to flowering, number of branches, number of mature seeds), nitrogen-fixing, (where relevant, for example, number of nodules, nodule mass, nitrogenase activity) and such other characters influence yield directly or indirectly.

Yield and most yield contributing characters are quantitative in nature. A quantitative character is one which shows continuous variation. In contrast, qualitative characters like flower colour and seed coat colour show, in general, discrete variation and are controlled by fewer genes with major effects. A quantitative trait, however, is governed by many genes. The range of values of a quantitative character is described by a continuous distribution, usually assumed to be a normal distribution. The distribution is specified by the two parameters: mean and variance.

Plant breeding is the purposeful manipulation of characters in plants to create new genotype with a set of desired characters. Hence, it may basically be referred to as designed manipulation of the heritable variation for the character concerned. Living organisms possess the remarkable capacity to convert the non-living materials into living staff, which results in movement, growth, metabolism and reproduction, and thus continuity of living organisms from one generation to the next is accomplished. The continuity of life through transmission of characters is the subject of the study of heredity, while the resemblances and differences between individuals of the same or different generations is the concern of the study of variation. These two universal processes of continuity and of change, which are referred to as “Heredity” and “Variation” are primary consequences of all organisms. Organized study of these two biological processes is the science of Genetics.
Plant breeding, which may be termed as evolution of plant type directed by the will of mankind, is basically the process of selection of character(s) from heritable variation. Desirable heritable variations can also be induced through some genetic consequences like, hybridization, segregation, mutation, changing the number of chromosomes, etc. So frame of plant breeding lay on three basics:

Biochemical reactions are mediated by enzymes and all enzymes are proteins. Proteins are polymers of subunits (monomers) called amino acids which are often termed as ‘residues’. Each amino acid has an amino group (NH ) at one end and a carboxyl group (COOH) at the opposite end. 20 different kinds of amino acids occur naturally in proteins. Each enzyme consists of a certain number of amino acids in a precisely ordered sequence. The blueprint for making proteins is coded in the nucleotide sequence of DNA. The number of nucleotides which code for an amino acid is termed a codon. There are 20 common amino acids but only four different nucleotides. Obviously a singlet code (one nucleotide coding for one amino acid) could code only for four amino acids. A coding sequence of two nucleotides for one amino acid or a doublet code would produce 4₂ = 16 possible coding combinations or codons and this arrangement is not sufficient to take care of 20 amino acids. A codon size of three nucleotides for one amino acid or triplet code seems more likely as it produces 4₃ = 64 possible codons as illustrated in Table 43.1 (Strickberger, 1968).

11.1 Introduction

In chapter 10, we have discussed the different types of variation, namely, genetic, environmental and genotype × environment interaction variations. We have also learnt how to estimate the phenotypic variance and its components including genotypic (also called genetic), environmental and g × e interaction variances from trial data. Now in this chapter, we shall discuss on the genetic components of polygenic (quantitative) variation and its implications on breeding strategies.

11.2 Genetic Components of Polygenic Variation

In this chapter whenever we call genetic variation, we mean polygenic (quantitative) variation, and we know that variation is usually measured in term of variance. However, variation, variability and variance are almost used synonymously. The genetic variance has been classified into different components by various workers. Fisher (1918) divided genetic variance into three components: additive, dominance and epistatic (interaction) variances. Wright (1935) classified genetic variance into two components: additive variance and non-additive variance (dominance and epistatic variances). Mather (1949) classified genetic variance into two components: heritable fixable variance (additive variance and additive × additive epistatic variance) and heritable non-fixable variance (dominance variance, and additive × dominance and dominance × dominance epistatic variances). Later, Hayman and Mather further divided the epistatic variance into three categories: additive × additive, additive × dominance and dominance × dominance.

Abstract

Most of the sorghum accessions are landraces, and much of the cultivated area of sorghum is under local land races. The local land races are highly adapted to specific environmental conditions and are useful sources of genetic variation. Under the present investigation one hundred and two local land races of sorghum collected from different geographical origins were evaluated during kharif 2010 and kharif 2011 in order to assess the genetic diversity. The analysis of variances showed highly significant differences among the accessions for all the characters studied.

ABSTRACT

India is the largest producer of banana, contributing to 17.3 per cent of the global production. In Kerala, it is the leading fruit crop, being cultivated in an area of 99,412 ha with an annual production of 7,31,650 tonnes. Biodiversity in the cultivars of banana, which consist of triploids, is complex especially in Nendran. Nendran belonging to Musa AAB plantain subgroup is the leading banana cultivar of the Kerala. in Kerala, several landraces are available, cultivated in different parts, known in different local names. Twelve Nendran ecotypes of banana belonging to AAB genomic group were collected from Banana Research Station, Kannara, Banana Nursery Farm, Palode and Instructional Farm, College of Agriculture, Vellayani to ana lyse genetic divergence using RAPD marker and morphological traits. Out of the forty one decamer primers screened for RAPD analysis, 34 could produce amplification. Twenty five primers showed high level of polymorphism. Finally, six of the most promising primers viz., OPA-01, OPA-03, OPA-13, OPB-04, OPB-10 and OPB-12 were used for RAPD analysis. Statistical analysis for the morphological traits and RAPD marker were conducted using the software programme NTSYS pc version 2.02e. The matrix average taxonomical distances (similarity coefficient) among the ecotypes ranged from 0.59 to 1.00 in RAPD profiles and morphological profiles (dissimilarity coefficient) ranged from 2.82 to 11.21. In the dendrogram (RAPD profiles), Koonoor Ethan showed the maximum genetic divergence. Quintal banana and Zanzibar came under a single clusters at a distance of 0.79 and clustered together at a distance of 0.82. Both the ecotypes showed next higher genetic divergence among the Nendran ecotypes. In the case of morphological traits, the same trend could be observed. Koonoor Ethan showed the maximum genetic divergence at a distance of 11.21 and Quintal banana showed next higher genetic divergence at a distance of 9.11. Koonoor Ethan, Quintal banana and Zanzibar were distinct ecotypes among the Nendran ecotypes of Kerala

Abstract

The genetic divergence among 249 germplasm lines of maize was assessed by D2statistics based on nine parameters at Agricultural Research Station, Karimnagar. The germplasm lines were grouped into eleven clusters. Clusters I and II were the largest clusters with 73 and 79 genotypes, respectively. The highest inter cluster distance was observed between cluster X and XI followed by cluster V and XI indicating more variability in the genetic makeup of inbreds included in these clusters. Cluster V showed highest mean values for grain yield/plant and ear length. Cluster XI had the lowest mean values for plant height and ear height and these two characters showed maximum contribution towards total divergence among different characters. Based on inter cluster distances, inter crossing among the genotypes belonging to cluster V, IX, X and XI has the chance of getting high yielding hybrids with higher heterosis.

Genetic architecture of a population is the result of prolonged natural selection. The populations which exist in diverse environments might have been strongly diversified genetically. So, it is necessary to understand the extent and rates of genetic divergence existing between the diversified forms or types. Genetic diversity may be available in improved germplasm or it may exist only in genetically inferior stocks.

Genetic divergence among the parents is important in self pollinated crops because a cross involving genetically diverse parents is likely to produce high heterozygous as well as heterotic effect. In such a cross, more variability could be expected in the segregating generations due to the accumulation of the genes of both the parents. Genetic divergence, as one of the criteria of selection of parents is considered in plant breeding as early as 1962 (Murthy et al., 1962; Timothy, 1963). Later, Joshi and Dhawan (1966), Murthy and Arunachalam (1966), Arunachalam et al. (1984) and Lefort-Buson (1987) also stated that for exploiting heterosis as a means of increasing production, it is necessary to have parents of maximum divergence. The more diverse the parents, more is the chance of pronounced heterotic effects and increased spectrum of variability in the segregating generations.

The availability of statistical tools to quantitatively measure the genetic divergence between two or more populations and the relative contribution of individual characters to the total divergence have permitted to trace the evolutionary patterns in some crops such as rice and tobacco and in choosing the parents for hybridization in crop plants (Rao, 1958; Blackith, 1960; Morishima and Oka, 1960; Murthy et al., 1962). Among the several statistical methods developed for measuring the divergence between the populations, multivariate analysis (D² statistic) developed by Mahalanobis in 1936, has been found to be a potent tool. Mahalanbobis’s D² statistic is an effective tool in quantifying the degree of divergence at genetic level and provides a quantitative measure of the association between geographic and genetic diversity based on generalized distance. It is now known that the estimates of genetic divergence are also influenced by environments and seasons. Therefore, if the divergence analysis is conducted in a number of seasons and parents are selected on the basis of consistent divergence over the seasons, the problem of influence of seasons on divergence analysis can be largely overcome.

Abstract

Genetic diversity of thirty two rice genotypes from different states of India was evaluated through Mahalanobis’s D2statistic under integrated fertilizer management for fourteen yield and quality characters. The genotypes were grouped in to seven different clusters. Cluster I had nine genotypes. Three genotypes each were included in cluster II, cluster IV and cluster VII, whereas six and seven genotypes in cluster III and cluster V, respectively while the cluster VI had only one genotype. The results revealed that the geographic diversity might not always be related to genetic diversity. Kernel length after cooking, days to maturity and kernel breadth contributed maximum towards divergence indicating their importance in choice of parents for the hybridization programme.

Date palm (Phoenix dactylifera L. Family-Palmaceae) also known as Khajoor or 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, which can be easily grown under saline conditions. Date palm grows as much as one feet per year, and as high as 80-100 feet under favorable environment. It is well known fact for date palm that its feet in the water and its head in sun. It requires dry hot climate for growth and development of fruits. In arid region, crop production is 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, other climatic requirements (Chandra et al, 1992, Singh et al, 2007). The date tree has religious significance. The fruits are used during holy month of Ramzan by Muslim peoples. As Saudi Arabia is principal producer of date palm in the world, the palm tree is incorporated in the national emblem of Saudi Arabia to represent vitality and growth

In recent years, we are just experiencing a surplus production in cereals and oil seeds leading to self-sufficiency through green revolution and yellow revolution. However, shortage in the production of vegetables has drawn the attention for increasing the cultivation of vegetables to provide food and nutrition security.

Vegetables are being cultivated over an area of 49 million hectares with the production potential of 487 million tonnes in the world. This accounts for 2.85 per cent of total cropped area in the world. India is the second largest producer of vegetables next to China, sharing nearly 12 per cent of the total world output (Joshi and Shukla, 1997). Vegetables occupy nearly 8.02 million hectares with the production potential of 133.10 million tonnes in the year 2009 in India (Anonymous, 2009).

Bhendi (Abelmoschus esculentus (L.) Moench) is an important member of family malvaceae and commonly known as okra or ladyfinger in India. It is one of the most ancient and traditional vegetable crops grown in tropical and subtropical regions of the world (Martin and Ruberte, 1978). Bhendi is originated from tropical Africa with 2n = 8x = 72 or 130 or 144 chromosomes and is an allopolyploidy in nature (Joshi and Hardas, 1956; Suresh Babu, 1987). Martin (1982) reported that it behaves as a diploid. Under the genus Abelmoschus, there are 30 species in the old world and four in the new world (Joshi et al., 1974). Out of them, Abelmoschus esculentus, is the only species known to be cultivated. Bhendi is being raised in India in an area of 0.44 million hectares with an average production of 4.52 mt with the productivity of 10.27 t/ha (Anonymous, 2009).

Introduction

India is the largest producer of pulses in the world, both in quantity and variety. But, presently, India is one of the largest importer of pulses. India imported pulse grains upto a tune of approximately 4000 crore rupees during 2006-07. It accounts for about 20 per cent of the total import bill during 2006-07. This is because of the green revolution (quantum jump in cereal production) accompanied with changes in the infrastructures and incentives including input supplies and price support systems in favour of major cereals. It altered the traditional cropping pattern against pulses with decades of emphasis on research as well as production in superior cereals coupled with a near total neglect of the rainfed areas, pulses were driven out of not only the irrigated areas, but also the rainfed farming and were relegated to the marginal lands. Further more, the weak infrastructural support for input supply, credit and marketing in the rainfed areas, the traditional home of pulses, also adversely affected the prospects for pulses. A vicious circle of low input use and low output thus got built in. Lack of processing and marketing facilities in pulses also contributed its share to the woes of pulse growers. The increasing shortage of pulses, resulted in the need for more and more import which, in turn has dampened the speed of rejuvenation of pulses sub-sector of agriculture sector.

The net per capita availability of pulses has fallen from 60.7 (1950-51) to 33.4 g (1991-92). On the contrary, the daily per capita availability of cereals has registered an increase from 334.2 (1950-51) to 443 g (1991-92). It leads to increase in the pulses/cereal ratio from 0.18 to 0.08 g i.e., by 55 per cent. This is despite the increases of 24.36 per cent in area; 61.71 per cent in production and 29.93 per cent in production. It is significant to note that almost all these increases had taken place during 1950-51 to 1960-61. The area, production and yield of pulses have either stagnated or declined since then. This stagnation of pulse production and productivity should be viewed seriously not only from the point of security and quality of food for our people, especially the poor and the rural population, but also from the soaring import bill, imbalance and distribution in the cropping pattern and resource allocation among various sub-sectors of agriculture.

The Coconut palm is a monotypic species of the family Arecaceae, under the tribe Cocoideae. It is considered as an important commercial crop in more than 18 countries in the world. The palm provides food, drink, shelter and also supplies raw materials for a large number of industries. Every part of the palm is utilized for some economic purpose or another. Hence, it is referred to as ‘Tree of Wealth” or the “Tree of Life” (Satyabalan, 1993). It is native of South East Asia. Genetic diversity has become one of the keywords of scientists who are concerned about the sustainable management of different tree crops. Genetic diversity plays an important role in tree breeding, because hybrids between populations of diverse origin, generally display a greater heterosis than between closely related parents (Zobel and Talbert, 1986). The present study was formulated to identify divergent parents for future breeding programme.

Two hundred and fifty genotypes of coconut cultivar Chawghat green dwarf, distributed in the two districts of Kerala viz., Kottayam and Pathanamthitta were evaluated for nut yield per plant during June-July, 2000. Seventy five genotypes, which had single tree nut yield of more than population mean ± 2 SE were selected as per the method outlined by Ledig (1974). These 75 genotypes were observed for 10 nut and endosperm characters in two seasons (years), during June-July 2000 and 2001.

Each tree was considered as a single genotype. Thirty nuts from a single tree were collected and divided into three replications (Chauhan and Kanwar, 2001; Thirugnanakumar, 2006a, b). Observations were recorded on 10 nut and endosperm characters viz.,1) oil content (%), cold percolation method; (Kartha and Sethi, 1957), 2) weight of unhusked nut (g), 3) weight of husked nut (g), 4) diameter (polar) of the husked nut (cm), 5) diameter (equatorial) of the husked nut (cm), 6) thickness of husk (cm), 7) husk: nut ratio, 8) thickness of meat (mm), 9) weight of kernel (g) and 10) weight of copra (g). The mean values so obtained were subjected to statistical analyses, in Randomized Block Design, as suggested by Chauhan and Kanwar (2001) and Thirugnanakumar et al.(2006a, b). The D² estimates were made following Mahalanobis (1936), as described by Rao (1952). Clusters were prepared following Tocher (Rao, 1952).

Gamboge tree Garcinia gummi-gutta (L.), is a member of the Clusiaceae family. It is a botanical cousin of Garcinia indica Choisy. It is a cross pollinated crop. It is called as Kodumpuli in Kerala. It is native of Tropical Asia. It thrives best in the ever green forests of Konkan, stretching from southward to the Kerala coast and Western Ghats upto 1800 m min the Nilgiris (CSIR, 1956). In Kerala, majority of the populations occur naturally in the central districts of Kerala, of different altitudes ranging from sea level to 200 m.

It is one of the potential under-exploited fruit crops. Now, it is gaining momentum for its commercial, industrial and medicinal importance. The dried rind is sold in the market at the rate of Rs. 200 per kg (Muthulakshmi et al.,1999). It is used as a food preservative, spicy source with astringent taste. It is meant for its good flavour, taste and keeping quality. The fruits are too acidic and cannot to eaten raw. The dried rind has unique use in fish curries for imparting its delicate flavour (Sarah, 1998). Dried rind can also be used for polishing gold, silver and coagulating rubber latex. Hydroxy citric acid (HCA) is a very rare natural components being extracted from the rind and is marketed in the name of ‘citrin’ and ‘citrimax’. It has high export value and fetches considerable foreign exchange. In foreign countries, it is used as a herbal medicine against cardiac diseases and for weight management through blocking fat synthesis. The derivatives of acid are potent metabolic regulators of obesity. The unique acid, lowers the blood lipids such as cholesterol and triglycerides by triggering the fatty acid oxidation in the liver through thermogenesis.

Introduction

The nature and magnitude of genetic variability present in the genetic stock afford the plant breeder, information to formulate a purposeful breeding programme for crop improvement. The association and the influence of yield components with yield, their heritability and genetic advance would characterise the various steps in the breeding programme in achieving the aim of the breeder. Studies on these lines in various crops have hastened the realization of crop improvement in general.

India grows a variety of pulse crop which probably no other country in the world grows. These are multiple utility, energy high crops as they provide protein for human consumption, green nutritious fodder and enrich soil fertility through biological nitrogen fixation. Vigna radiata (L.) Wilczek, commonly known as greengram or mungbean, is the most widely distributed of the six cultivated Asiatic Vigna species.

The current breeding approaches to yield improvement in greengram are based on the recognition that this crop have lost a large part of their genetic variability in the process of adaptation to stress environment. This variability must now be regenerated.

The foremost need for this purpose is the collection of germplasm from different parts of the world and the organisation of a very intensive hybridization programme, using diverse genetic stocks as parental lines. Selection of parents for hybridization based merely on geographic diversity can no more be a suitable criterion. The importance of genetic diversity has long been appreciated by crop specialists. Such an analysis will eventually help to choose desirable parents for hybridization and evolve superior genotypes.

Jack bearing the largest edible fruit in the world, is a tropical evergreen tree belonging to the family Moraceae. Previously, it was known as Artocarpus integrifolia.It is an indigenous fruit crop, probably originated in Western Ghats of India (Santapau, 1966) and is widely cultivated in South Asia, East Indies and other warm areas of both the hemispheres. Jack tree is commonly grown in Burma, Malaysia and Brazil. It is hardly recognized as a commercial fruit crop in India even though it is widely distributed in Southern states viz,. Kerala, Tamil Nadu, Karnataka and Andra Pradesh. It is also cultivated in other states like Assam, Bihar, Orissa, Maharashtra and West Bengal. It is an invariable component of Kerala’s homesteads and also grown as a shade crop in coffee, arecanut and cardamom plantations. It is also grown as a standard crop in pepper plantations. The crop has got a rare distinction of being used as the staple food of Kerala tribals and also in some African countries like Uganda.

The mango is one of the choicest fruit crops of tropical and sub-tropical regions of the world. Its popularity and importance can easily be realized by the fact that it is referred as ‘King of fruits’ in the tropical world. India ranks first, both in area (2.51 million hectares) and production (15.02 million tonnes) of mango and it contributes to 42.1 per cent of world’s mango production. Presently, India is home to more than 1000 mango cultivars differing in taste, aroma, size, fibre content and pulp characteristics.

Though more than 1000 mango cultivars are reported, only 25-30 are of commercial importance. Most of the important cultivars are not amendable to hi-tech cultivation practices and do not meet the requirements of modern horticultural production systems like precocity in bearing, dwarfing, regularity in bearing with high yield, resistant to diseases, pests, physiological disorders and good keeping quality. Hence, breeding attempts to develop an ideal mango variety would be dwarf, regular bearer with medium size fruits (250-300g). Additionally, it should be highly tolerant to various fungal and bacterial diseases. A variety suitable for pickling is also gaining the attention of the breeders. An ideal pickling type should have high acidity, high fibre, good texture and characteristic raw mango flavour.

The first and foremost step in developing an ideotype is to explore the vast diversity and systematic characterization for utilization in the breeding programme.

Considering the importance of conserving the available gene pool, systematic exploration works are being carried out by National Institute like Indian Institutes of Horticultural Research (IIHR, Bangalore), National Bureau of Plant Genetic Resources (NBPGR, New Delhi) and others to collect and conserve the germplasm in Field Gene Banks. Recently, in addition to the traditional germplasm conservation methods, cryopreservation is also gaining importance especially in the conservation of nuclear gene (pollen parent) diversity for future breeding.

Utilizing the conserved germplasm in the breeding programme requires precise information on the genetic relationships within such germplasm. Information on the genetic distance among the germplasm accessions will also help to avoid the duplicates, widen the genetic base of the core collections and ultimately help in preserving the valuable diversity.

Pomegranate is one of the popular fruit crops of tropical and sub tropical in India and enjoys high reputation for its dietetic and medicinal properties. The fruit is native of Iran and is extensively cultivated in Mediterranean countries like Spain, Morocco, Egypt, Iran, Afghanistan. It is also grown to a lesser extent in Myanmar, China, Japan, India and U.S.A.

The area under pomegranate cultivation has increased several folds in the recent past after the introduction of soft seeded varieties. Out of 30,000 hectares under this crop in India, Maharashtra state alone grows over eighty per cent of area with an average production of 8000 kg ha^-1 (Mote et al.,1992). The export of pomegranate fruits was 1790.3 tonnes in 1991-92 valued at rupees 215.3 lakhs which was more than two fold over the previous year’s export earnings (Chadha, 1994). The utility of the crop is gaining importance and at present new orchards of pomegranate are being planted on large acreage. Because of its versatile adaptability, hard nature, low maintenance cost, steady and high yields, fine table and therapeutic values, better keeping quality and very good export potential, there is greater scope for extending its area and increasing the production especially in the hot and semi arid regions of India.

In pomegranate, market preference is for the attractiveness of the fruit which are exhibited through better size, colour with bold and deep coloured arils besides possessing high juice-content. However consumers prefers the softness of the arils with low acidity. While, there are number of cultivated types available with these desirable characters, there are hardly cultivar having a combination of all or atleast a majority of them. Pomegranate improvement work, therefore has to be oriented towards the production of soft seeded type with other desirable characters (Phadnis, 1974).

Rice (2n = 24) is an annual grass (family: Graminae) with terminal panicles bearing the grains. It originated in Asia between the fourth and fifth millennia B.C. A substantial portion of the people in south and Southeast Asia and the southern part of China are depending on rice as staple food (Chang, 1976). Rice is planted in the most diverse environmental conditions of any major food crop, from sea level to around 3000 m altitude and from 30°S to 49°N. Temperature and day lengths are therefore quite diverse in the rice growing areas. Rice is also grown under water regimes ranging from dry land to deepwater fields where water may reach 5 m depth. The wide geographical distribution of rice and its early history of cultivation have resulted in the development of a great diversity of varietal types (Vergara, 1985).

Rice has been used as food by man for over 10,000 years and has fed a great number of people for a longer period than has any other crop. “Rice is life” for almost four billion people of the world contributing over 20 per cent of the total caloric intake of human population (Chaudhary and Tran, 2001). Rice is cultivated in 113 countries and on all continents except Antarctica and it is the staple food for 17 countries in Asia and the pacific, eight countries in Africa, seven countries, in Latin America and the Caribbean and one in the near east (IRC, 2003).

Globally rice is grown in around 155 million ha occupying one tenth of arable land, with an annual production of 579 million tonnes of rough rice (Iiyas Ahmed, 2003). The average productivity of 3.89 t ha^-1 of rice provides a per capita. Consumption of 100 to 240 kg per year across the globe. Over 90 per cent of the world’s rice is produced and consumed in Asia and more than half of it from India and China exploiting maximum arable land. More than two billion people obtain their 80 per cent calorie from rice and its derived products from 90 per cent of world’s rice area (FAO, 1999). Rice based on production systems and their associated post harvest operations employ nearly a billion people in rural areas in developing countries (IRC, 2003).

In recent years, we are just experiencing marginal surplus production in cereals leading to self-sufficiency through green revolution. However, the shortage of production in edible oils has drawn the attention for the increased cultivation of oil seeds, and increased productivity per unit area to provide sustainable food and nutrition security (Swaminathan, 1989).

The importance of oil seeds cannot be over emphasized in the Indian economy. Oilseed occupied nearly 19 million hectares, next only to food grains, in 1986-1987. Yet, the domestic production in the country has lagged far behind the increasing demand for edible oils, necessitating a massive import of edible oils which lead to the drain of the valuable foreign exchange. The total import bill on edible oil has increased from 1.41 per cent in 1970-71 to 3.05 per cent in 1986-87. Even then, the annual per capita availability of edible oils registered only a nominal increased from 3.5 kg to 5.9 kg during the same period, against the nutritional norm of 14 kg (Suresh Pal, 1989). Due to the concerted efforts made through the ‘Technology Mission on Oilseeds’, oil seeds production reached a peak of 178.9 lakh tonnes during 1988-’89 in India (GOI, 1990a). This is an impressive achievement in Indian Agriculture, to reduce the bill on the import of edible oils from 4.11 per cent (1987-’88) to 2.58 per cent (1988-’89) (Gill, 1990). Further efforts in increasing oilseeds production definitely will go a long way in drastically reducing the present import bill.

Among the oilseed crop, sesame (Sesamum indicum L.), “The Queen of Oil Seeds”, is one of the important ancient and traditional crops occupying third position in terms of acreage on the oilseeds map of the country. It is commonly known as Gingelly, Til, Benniseed and Simsim. It is an important source of edible oil for the nutritional refugees of most part of the world, especially for India. The oil is rich in oleic and linoleic acid. In addition, it serves as a good source of proteins, vitamins and minerals (Nagaraj, 1990). Its high keeping quality deserves special mention.

ABSTRACT

The investigation aimed at to examine the diversity among nineteen wild and cultivated germplasms of the genus Vigna namely, V. trichuriensis, V. hainiana, V. radiata, V. aconitifolia, V. minima, V. sinensis, V. radiata var. sublobata, V. radiata var.setulosa, V. umbellata, and allopolyploid of BR3x T9 at DNA level follwing Random Amplified Polymorphic DNA (RAPD) technique. Ten random decamer primers were used in amplification reactions, five of that were reproducible and clear. The five primers constituted 55 bands of, which 9 are polymorphic. The similarity index based on 0 and 1 matrix of banding was calculated and dendrogram following UPGMA was constructed. The germplasms formed altogether 4 clusters on the basis of 0.375 linkage distance. The first and second cluster consisted of single genotype of V. hainiana. and V. minima respectively. The third cluster comprised wild and cultivated types of V. sinensis. The 4th cluster on the otherhand, consisted of genotypes belonging to V. radiata, V. radiata var. sublobata, V. mungo, V. radiata var. setulosa, V. trichuriensis and allopolyploid of BR3 and T9. The wild forms of different species were found to exist in the same cluster as their cultivated form. The three mungbean genotypes namely B105 (V. radiata), B1 (V. radiata) and BR3 (V. radiata )are crossable within themselves and they belonged to the cluster -IV.The intercluster cross between different clusters would like to generate new genotypes with wide variability. Based on limited range of accessions tasted in the present investigation, the approach holds promise for the classification of Vigna germplasm, identification of Vigna and marker assisted breeding in Vigna.

Introduction

Genetic resources are the building blocks for new varieties. The Indian gene centre is floristically extremely rich. Most of the tropical and sub-tropical fruits believed to have originated from Hindustan and Indo Malaya-Region. Hindustani gene centre possess a rich diversity of 152 crop plants distributed in different agro-ecological regions of India (Arora, 1985). The Indian sub-continent is one of the centers of origin and diversity of vegetables crops. Around 80 species of major and minor vegetables occur in wild forms (Choudhury, 1967, Seshadri 1987). Among the 118 genera belonging to the Cucurbitaceae family Cucurbita, Cucumis, Citrullus and Lagenaria genera are of great importance. There is tremendous genetic diversity within the family, genera and even within species level. The adaptation range varies from tropical and subtropical regions to extreme arid desert and in temperate regions from Tarai belts to higher altitudes. Extreme germplasm collections are maintained at different centers of the world which represents valuable resources for breeding even in wild form, primitive cultivars, landraces/ folk varieties/ farmer’s selection in a much localized pockets. Now we have very good strains for highly nutritive value, multiple disease resistant and extended shelf lives from our local material through intensive breeding.

Indigenous plant germplasm are adapted component of plant biodiversity. Such adapted components are more valuable resources either as a cultivar or as a parental line in hybridization programme. It might be also a putative material for biotechnological treatment for tolerance to biotic, abiotic factors or nutritional and quality components. Indigenous germplasm can be basically of two types, one which has been domesticated and subjected to human intervention, the other one may be called wild plants or wild relatives and still in the process of evolution without the human intervention. Biochemically the cucurbits are characterized by bitter principles, called cucurbitacins. Great variety of cucurbits contains bitter principle in portion of the plant at some stage of development. Cucurbitacins are tetracyclic triterpenes having extensive oxidation level. Bitter principals found in roots differ from those in fruits. Seedlings specially radicals contains cucurbitacins which are considered primary. The pollen also carries bitter principles and hence when bitter pollen fertilized non-bitter ovule the resulting fruit will be bitter known as metaxenia effect. Cucurbits are consumed in various forms i.e. salad (cucumber, gherkins, longmelon), sweet (ash gourd, pointed gourd), pickles (gherkins), deserts (melons) and culinary purpose. Some of them (e.g. bitter gourd) are well known for their unique medicinal properties. In recent years, abortifacient proteins with ribosome-inhibiting properties have been isolated from several cucurbit species, which include momorcharin (from Momordica charantia), luffaculin (from Luffa operculata), trichosanthin (from Trichosanthes kirilowif) and beta-trichosanthin (from Trichosanthes cucumeroides). Among these, Trichosanthin is of particular interest because its ribosome-inhibiting properties have been found to be effective in inhibiting the replication of human immunodeficiency virus (HIV), indicating its potential as a therapeutic agent for AIDS. In cucurbits three conditions are found (i) fruit and vegetative parts bitter (ii) fruit not bitter but vegetative parts bitter (iii) bitterness absent in both vegetative parts and fruits. Hence some kind of co-evolutionary relationship between cucurbits found and they are very helpful during evaluation of germplasm.

Introduction

Diversity connotes multiplicity of variety. In a given ecosystem, diversity refers to presence of number of different species of ?ora and fauna that have ecological niches in agreement with the environment. Scaling up, there exists diversity between different ecosystems. All life forms of ?ora and fauna on earth contains genetic material, that is the repository of an immense amount of genetic information in the form of traits, characteristics, etc. Focusing on the species level, genetic diversity refers to genetic variation that is observed in a population. Thus, genetic diversity is the total number of genetic characteristics in the genetic makeup of a species. This provides in built latitude to the nature and/or the livestock breeders (including farmers) to manoeuvre/ manipulate so as evolve an improved population of desired qualities and traits. Further, genetic diversity is essential because the presence of adequate and appropriate genes in a population will make the species tide over adversaries owing to climate change and other emerging threats like new disease outbreaks. The ‘desired’ divergent gene pool provides the inherent resilient mechanism that equip the species to cope with likely challenging situation.

Over the years, with human interventions, the genetic diversity has been interfered with to meet specific needs; mostly with respect to garnering higher production and productivity. In the process, the diversity has been compromised for achieving the unitary goal. In certain cases, geographical barriers and other bio-physical constraints have also led to loss of diversity within a population. Studies on impact of climate change especially the effect of rise in environmental temperature on milk production of dairy animals indicate that global warming will negatively impact milk production. During 2020, the annual loss in milk production of cattle and buffaloes due to thermal stress will be around 3.2 million tonnes of milk costing more than Rs 5000 Crore at current price. Similarly, there would be prevalence of many emerging diseases including those with zoonotic implications owing to change in climatic conditions. Thus, the present day society is confronted with an imminent development dilemma of ecology vs. economics more specifically genetic diversity vs. higher production. It has led to volume of debates and discussions on the livestock development agenda to be pursued. The apparently con?icting interests has also generated antipathy amongst two schools of development.

Ralstonia solanacearum is a phytopathogenic bacterium belong ing to the b subdivision of the Proteobacteria (Yabuuchi et al., 1995) having a wide geographical distribution ranging from tropical, subtropical and warm temperate regions (Liu et al., 2009). It has broad host range and infects around 54 plant families and 450 plant species (Hayward, 1991; Wicker et al., 2007). 

Early attempts to study the diversity present in the R. solanacearum species complex resulted in separate race and biovar systems. R. solanacearum has been phenotypically classified into 5 races based on the host range at the plant species level and into five biovars based on the metabolic profiles related to the ability to reduce three disaccharides and three hexose alcohols (Wicker et al., 2007).

Vegetables are of short duration, have higher productivity and give more return per unit area, besides giving nutritious food to human being and can be fitted in different farming systems. They also play a major role in balancing human diet, thereby helping in alleviating hunger, poverty and malnutrition. Because of the public awareness for the significance of vegetable consumption, the demand of vegetables in the global market has increased immensely. Thus, vegetable farming is becoming profitable venture globally, opening avenues of self employment and revenue generation (Anon., 2009). At global level, India holds second position, next only to China in vegetables production with a share of about 14%. The present annual vegetables production of country is about 175 million tons from an area about 10.3 million ha with a productivity of 17.1 t/ha. India grows largest number of vegetables in the world, as having a spectrum of wide range of agro-climatic situations, ranging from dry temperate to humid tropics between the altitudes from sea level to snow line.

The Indian hot arid region is one of the most important arid ecosystems of the world in terms of biodiversity it possesses. This arid region spreads over 31.7 mha, occupies major part of north western India including Rajasthan, Gujarat, Punjab and Haryana, which together contribute 73% of arid region. High temperature, wind velocity, low humidity, low and erratic rainfall and high potential evapotranspiration are important characteristics of this region which narrowed down the choice for vegetables, besides permit their low productivity.

Abstract
Understanding genetic diversity is essential for achieving genetic improvement and conservation of grain legumes. These crops serve as important pulses grown and consumed all over the world, especially in Africa, South East Asia and America. Legumes serve as a good source of carbohydrates, oil, fibre and proteins. Grain legumes are a major source of food and nutrition globally. However, it has not been possible to enhance gain legume production to the required level, primarily due to the narrow genetic base of most of the legume crops, coupled with changing climatic conditions. Most grain legumes are lacking in desired plant ideotypes and resistance sources for various biotic and abiotic stresses. The genetic diversity conserved in gene banks globally is a major resource for crop breeding programs, but it
is utilized only marginally. Therefore, in order to broaden the genetic base of grain legume crops and enhance the genetic gains made in improvement programs, conventional approaches and modern scientific tools should be integrated in a phased and carefully judged manner. The first phase should focus on the search for desired traits and the infusion of diversity into the cultivated gene pool through use of landraces and CWRs. The second phase should focus on the utilization of advanced selection tools, such as genomics, high-throughput precision phenotyping, and artificial intelligence, to exploit the hidden potential of the available genetic diversity; and the third phase should involve technologies such as mutational breeding, genome editing, and transgenic technologies to improve, modify any novel or alien traits that are not available in the entire crop gene pool. We presume that enrichment of the genetic diversity of cultivated grain legume gene pools, along with simultaneous improvements in their yield and plant type with the aid of advanced scientific tools, will enhance grain legume crop yields to the required level.
Keywords: Crop improvement, Genetic diversity, Genome editing, Legume, Phenotyping