Preface Genetic diversity plays an important role in crop evolution. Assessing diversity by morphometric through classical plant breeding is very much useful to study the crop evolution and to identify suitable parents for developing superior progenies. The genetically diverse parents will show high combining ability resulting in high heterosis in F1 generation and throw some useful segregants in the F2 and in later segregating generations too. Genetic diversity has been classically measured with Mahalanobi’s’ D2 method. Diversity analysis over season and environments also gives useful information in identification of suitable parents. The consistent genetic diversity over seasons and environments would be useful in practical plant breeding. Further, genetic diversity has also being measured with molecular markers to avoid environmental interaction. On the other hand, phenotypic stability among genotypes is very important in actual plant breeding. Among the various methods adopted to measure phenotypic stability, the method outlined by Eberhart and Russell gains momentum, as it is simple and explicit in nature. Phenotypic stability parameters has been collectively utilized to classify the genotypes as having high stable genotypes with average responsiveness as well as genotypes suitable for favourable as well as unfavourable environments. The authors have taken concerted efforts to bring useful information on genetic diversity and phenotypic stability among various field and horticultural crops for the researches who involved in crop improvement program. Further, the authors welcome suggestions from readers to improve this book further.

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 must be sufficient enough to justify breeding effort. Genetic diversity may be available in improved germplasm or it may exist only in genetically inferior stocks. 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 population, multivariate analysis (D2 statistic) developed by Mahalanobis in 1936, has been found to be potent tool. Mahalanobis D2 analysis is an effective tool in quantifying the degree of divergence at genetic level and provides a quantitative measures of the association between geographic and genetic diversity based on generalized distance.

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.

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.

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.

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).

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).

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).

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.

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.

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.

Rice (Oryza sativa L.) is the most popular crop and source of food for more than one-third of the world’s population. About 90 % of the world’s rice is grown in Asia and more than 3 billion Asians rely on rice for 30–75 % of their total calories (Braun and Bos 2004). It has been cultivated in four different ecosystems viz., irrigated, rainfed low land, upland and flood-prone (Halwart and Gupta, 2004). Since rice planting has been started around 8,000 to 9,000 years ago, the level of diversity would be more than it expected. The genetic diversity plays a major role in survival and adaptability of a species, as changes happen in environment. Organism needs to make changes in the phenotype that enables it to adapt and survive in unfavorable conditions. The inadequate knowledge on diversity of a species reduces the chance of widening the genetic base of that species. The venture of green revolution in Indian agriculture has narrowed down the genetic base of any popular crops. Therefore, collection, conservation and utilization of germplasm are very much needed in the present scenario for improving the varieties against biotic and abiotic stress. Morphological and biochemical trait based diversity studies being largely influenced by environment as phenotype and/or enzymes are altered by the environmental and developmental changes. Therefore, adapting DNA based molecular markers for genetic diversity studies would be more reliable to overcome the environmental influence. Being molecular markers as a versatile tool, it establishes its strong holds in several fields of life science. Molecular marker based technique does not require DNA sequencing but it is generally based on nucleic acid hybridization or polymerase chain reaction (PCR). The PCR based tests has several advantages over hybridization technique as it is cheaper, speedy and sensitivity. Therefore, PCR based markers have been used extensively in genetic diversity study for assessing genetic variation within the species. The recent advent of molecular and computational tools now enables the estimation of genetic diversity and allele frequency between the genotypes easy.

A successfully developed new cultivar should have stable performance and broad adaptation over a range of environments, seasons and locations, in addition to high yield potential. Evaluating performance stability and range of adaptations is becoming increasingly important in breeding programs. Since stability and adaptability are important selection criteria in breeding programs, in depth research on stability is needed for a better estimate of crop performance and adaptability (Lin and Binns, 1988). Having realized the importance of genotype × environment, several biometrical models have been developed to analyse the stability of genotypes. Such models have been discussed, critically reviewed comprehensively by Knight (1970), Freeman (1973), Hill (1975), Brain (1986) and Gautam et al. (1986). However, the various methods proposed for the statistical analysis of genotype × environment are based on one of following approaches (Jain, 1982). In the first the variance interactions are estimated by equating the observed mean squares in the analysis of variance to their expectations on the random model. The second approach called phenotypic approach by Hill (1975) used the technique of partitioning the genotype × environment component of variability into its linear and non-linear portions of assessing the stability of genotypes over a range of environments. This approach which is very widely adopted in plant breeding, came to be known as “Joint regression analysis”. Many workers contributed for the development of this approach, notably Finlay and Wilkinson (1963), Eberhart and Russell (1966), Freeman and Perkins (1971) and Shukla (1972). The third approach called genotypic approach which also suggested by Hill (1975) is based on fitting of general models in which it specify, the contribution of genetic, environmental and genotype × environment to the generation means and variance. The contributions for he development of this approach were from Bucio (1966), Bucio and Hill (1966), Bucio et al. (1969), Perkins and Jinks (1968), Breese (1969), Hill and Perkins (1969) and Perkins (1970). Linear regression and joint regression models were more commonly used due to their simplicity and reliability in biological experiments. In general, these approaches fall conveniently into two parts.

Stability and adaptability studies have been carried out for upland or hill rice varieties also. Amirthadevarathinam (1987) observed significant genotype × environment and reported that both linear and non-linear components were equally important for assessing stability of yield and four yield components in four environments. Both TKM 6 and Poongar were high yielding with adaptability and stability in addition to being especially suitable for unfavourable environments. Kuruvaikalangium was the best performer for all characters except grains per panicle for which PM 1023 was the best. Dineshkumar (1987) evaluated sixteen early maturing genotypes for their stability in four major agroclimatic zones of the Karnataka state. No genotype was found stable as they observed more of unpredictable variance (pooled deviation) than predictable (genotype × environment linear). Ganesh and Soundarapandian (1987) observed that stability of number of ear bearing tillers was a major contributor for yield stability Shivaprakash (1987) reported similar results. Studies by Sinha and Biswas (1987) on yield and yield components of twenty photo insensitive rice cultivars revealed IR-36 and IET-4094 as high yielder with unit ‘bi’ and least ‘S2 di’ and hence they were recommended to be suitable for general cultivation for all the environments under study. Similarly IET-2881, which had high mean yield with high ‘bi’ was found suitable for high yielding environments.

Genotypes × Season interaction is of major importance to the plant breeder in developing stable high yielding varieties of crop plants. When new varieties are tested over a series of seasons, the relative ranking of the varieties for any given attribute is rarely the same at each season. This increases the difficulty of identifying superior stable genotypes. Comstock and Moll (1963) have shown statistically the effect of large genotype × environment interaction is reducing the progress from selection. In order to minimize the genotype × season interaction, stratification of the seasons can be practiced. The implification in stratification is that suitable selections could be made for the infavourable and favourable seasons encountered within the sampling units proposed. Stratification of environments has been practicised for a long time to identify suitable selection that could be made for the narrower range of environments encountered within the sampling units proposed. However, even with this refinement of technique, the interactions of genotypes with locations in a sub-region and within environments encountered at the same location in different years, frequently remain too large (Allard and Bradshaw, 1964). Little is known about the environmental factors contributing to such interactions. Sprague (1966) suggested that even if such information are available, the possibility of materially reducing genotype × environment interaction in field experiments would remain questionable. On line with Allard and Bradshaw’s (1964) statement, the interactions of genotypes with locations in a sub-region with different seasons at the same location in different years, may remain too large. As far as sesame is concerned, practically nothing is known about the factors contributing to such genotype × season interactions. Hence, the progress in breeding a stable variety of sesame has been slow. Since sesame in India is grown essentially as rainfed crop, fluctuations in yield levels closely follow changes in the environment and seasons. Breeding for multiseasonal variety for may small regions within a state is being considered necessary. There is widespread awareness of achieving stability of production as well as improvement in yield of sesame under low and high-in-put conditions as well as for different seasons.

In developing countries, the most important challenges is to increase food productivity for the continuously growing population from limited land area. To great extent, this challenges has been met with good amount of success in cereals but not in case of pulses. Pulses from an indispensable component of Indian agricultural too. Further, it is an excellent source of protein to the growing population who are mostly vegetarians. The high level of lysine in the protein makes them ideal supplement to cereals. Moreover, they are endowed with nitrogen fixation, and thus improve the soil fertility. India is one of the major pulse growing countries in the world with a total area of 23.31 million hectares, with a total production of 14.50 million tones (Source: FAO, 2011). The area, under pulses has decreased particularly during the last decades as a consequence of intensive diffusion of techniques in green revolution on the high yielding varieties of cereals. This is mainly due to the low yield potential of legumes even under high input conditions. Among the various pulses, blackgram/urd bean known scientifically as Vigna mungo (L.) Hepper, former known as Phaseolus mungo (L.) belonging to the tribe Paseolea of family Papilionaceae is of immense importance. It is the most widely grown and highly esteemed grain legume. In India it occupies 2.9 million hectares with an annual production of 1.24 million tones (Source: FAO, 2011). In Asia this crop is widely cultivated in India, Pakistan, and Bangladesh both in kharif and rabi seasons. In India, it is mainly grown in the states of Madhya Pradesh, Maharashtra, Uttar Pradesh, Rajasthan, Karnataka and Bihar. Tamilnadu is placed eleventh and tenth in area and production respectively (FAO, 2011).

Ramya (2012) studied stability of 12 hybrids in three environments. The researcher selected the 12 hybrids based on the standard heterosis. The hybrids are: P2 × P5, P1 × P5, P3 × P5, P2 × P7, P2 × P3 and P1 × P2. Among the twelve hybrids, the cross combinations viz., P2 × P5, P2 × P7 and P2 × P3 showed non-significant reciprocal effects for most of the traits including fruit yield per plant. The direct hybrid P1 × P2 showed less than 40 per cent standard heterosis for fruit yield per plant. It also exhibited low standard heterosis for number of fruits per plant. Eight hybrids viz., P2 × P5, P5 × P1, P3 × P5, P2 × P7, P1 × P5, P2 × P3, P2 × P1, P5 × P3, based on standard heterosis (>40 per cent) and their parents viz., P1, P2, P3, P5, P7 were selected and grown in three different locations for finding their stable performance. Several authors have suggested different types of models to identify the stable genotypes. The model most commonly preferred by breeders is Eberhart and Russell (1966) model which was used in the present investigation. Various stability parameters were worked out on the available data and the results were discussed below. Among the ten traits studied, days to first flowering, fruit weight and fruit girth showed non-significant genotype × environment interaction. Hence, the remaining seven traits were taken for further analysis. ANOVA across environment revealed highly significant mean sum of square for genotypes, indicating the presence of wide genotypic variability among the genotypes involved in the study for all the characters studied. High significant differences were observed for environments for the traits viz., number of branches per plant, fruit length and fruit yield per plant, indicating the divergence among the growing environments and differential response of genotypes to the various environments. The main factors contributing to the divergence of the environments might be temperature differences during crop season, intensity and duration of sun shine hours. Therefore, the genotypes must be tested over an extensive range of environments for proper assessment of stability of genotypes (Salesh Kumar Jindal et al.,2008).

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