eChapters

The students in batches will visit the laboratory of Plant Pathology for their acquaintance with different appliances, tools, glassware‘s and other miscellaneous items, which they will use for various exercises and experiments to be conducted. A list of some of them is given below:

2.1    Introduction

The hot and usually wet conditions in tropics adversely affect the performance of insecticides as well as biology of the pests. Pesticide usuage is declining throughout the world, but in tropics it is likely to increase threatening basic biological components of pest management, environment and safety of people.  Pest management in tropical agriculture is basically influenced by high diversity of organisms, diversity of physical features and ecosystems, moderate seasonal weather changes, and the human factor. The high biological diversity of the tropics includes a wide range of interacting organisms from which have been identified pests that affect health crops and livestock as well as cultural practices for pest management.  Physical features of the tropics are also diverse, and include high-altitude temperate zones, rain forests, savannah woodlands, grasslands, and desert zones. Each zone has its own biological diversity either existing in isolation or overlapping with others. Moderate seasonal weather changes in the tropics affect populations indirectly, through modification of interactions between organisms.

Antirrhinum is a genus commonly known as snapdragon belongs to family Scrophulariaceae. Snapdragon is one of the flowering plant present with vast genetic diversity in India. The term Antirrhinum is derived from the Greek word “anti” means like and “rhin” means a nose, referring to the snout like shape of the flower. The cultivated Antirrhinum majus is grown in tropical, subtropical and temperate countries. The common name snapdragon, originates from the flowers reaction to having their throats squeezed, which causes the mouth of the flower to snap open like a dragon’s mouth. Flowers are borne on terminal long spikes of many colours except blue and with numerous shades. It is one of the excellent cut flowers which have long lasting qualities. These are also used as garden plants, bedding plants, in rockeries or herbaceous borders and as potted plants. Plants can be grown for cut flowers in an open field or under protection depending on the climate. The leaves and flowers are antiphlogistic, bitter, resolvent and stimulant (Chiej, 1984).

ORIGIN AND DISTRIBUTION

The garden snapdragon (Antirrhinum majus) has emerged as a model organism during early studies of inheritance and mutation (Darwin, 1868) because of its diploid inheritance, ease of cultivation and variation in morphology and flower colour. The genus Antirrhinum includes 15 New World species in the section Saerorhinum and 21 Old World species in the sections Antirrhinum and Orontium. A. majus (Snapdragon) is a species of Antirrhinum native to the Mediterranean region, from Morocco and Portugal north to southern France and East to Turkey and Syria. Most species are found around the Mediterranean Sea and in North America (Stubbe, 1966). The progenitor of the modern snapdragon is from the Mediterranean region and more specifically, it is native to southern France. It was believed that the snapdragon reached Britain with the Romans at an early date, where it has been naturalized on mountainous regions. Thereafter, it spread to different parts of the world from Britain.

The scientific name of the genus Antirrhinum was first defined by Carl von Linne in the year 1753. In the year 1914 Professor Erwin Baur the founder of the MaxPalnck-Institut für Züchtungsforschung in Cologne published a volume called ‘Einführung in die experimentelle Vererbungslehre’ (Introduction to Experimental Genetics) 2nd edition. This book contained several plates with reproductions of water colour paintings of snapdragons as examples. He crossed a white line with a red line resulting in a pink flower. This pink flower then was selfed and the offspring showed the typical distribution of 1 white, 2 pink and 1 red as a demonstration of Mendelian inheritance. Antirrhinum glandulous is native of California. In United States of America, winter flowering cultivars were introduced in 1926 by Frank Volz of Cheviot, Ohio. In 1959, snapdragon were included in the Agricultural Censuses of Horticulturally Special Crops and ranked seventh as a cut flower crop.

The genus Antirrhinum offers an inexhaustible resource for genetics-based studies in developmental biology, biochemistry and evolution (Stubbe, 1966). Wide diversity of Antirrhinum species, combined with classical and molecular genetics, the two traditional strengths of Antirrhinum provides an opportunity for developmental, evolutionary and ecological approaches (Schwarz-Sommer et al., 2003). Transposons responsible for flower variegation were identified in the 1980s. The Max-Planck-Institute in Cologne, Germany, allowing genes involved in flower and leaf development and in pigmentation to be isolated by transposon tagging. Population genetic studies that have been applied to Antirrhinum species show different population sizes, geographic distributions and breeding systems, from self-fertility to obligate out-crossing (Jimenez et al., 2002 and Mateu-Andres and de Paco, 2006). It was introduced to India with the advent of British. Among them, only A. majus has been domesticated as an ornamental.

Anthurium (Anthurium andraeanum Linden) belongs to the complex family Araceae, is a slow growing perennial that requires shady, humid conditions as found in tropical forests. The name anthurium is derived from Greek word “anthos” meaning flower and “oura” tail referring to the spadix. Thus, anthurium is also known as “tail flower” (Tajuddin and Prakash 1996). Anthuriums are gaining popularity due to higher returns per unit area and their beautiful and attractive long lasting flowers. Anthurium ranks ninth in the global flower trade and commands a respectable price both for its cut flower and whole plant. Commercial production has focused on two major species viz. A. andraeanum and A. scherzerianum. A. andraeanum is grown mostly for cut flower production, the main production areas being Hawaii, The Netherlands, and some other tropical and subtropical countries. A. scherzerianum is sold as a flowering potted plant, with main production areas located in Europe. In India, the anthurium cut flower industry is still in its infancy. At present anthuriums are mostly grown in some small gardens and nurseries. The important states cultivating anthuriums are Assam, Kerala, Tamilnadu (Salem), Karnataka (Coorg) and Mizoram where the favourable climate exists (Agasimani et al., 2011).

ORIGIN AND DISTRIBUTION

Anthurium andreanum Linden Ex Andre is named after a French Horticulturist Edouard Francois Andre (1840-1911) who discovered it in 1876 and described it for the first time. The genus includes around 1000 species (Croat, 1980). Most of them are tropical herbs originating from warm areas of Central and South America (Gantait et al., 2008). The distribution of this genus extends from northern Mexico and the Greater Antilles to southern Brazil, northern Argentina, and Paraguay (Croat and Sheffer, 1983). Most anthurium species are native of tropical rain forests and are primarily epiphytic in nature. Thus, in their natural habitat, they receive ample, frequent water with good drainage. In Brazil, it is noted the occurrence of around 130 native species (Gonçalves, 2003).

In Malaysia, anthurium is mostly grown in Pahang (Cameron highlands), Selangor, Perak and Johor mainly for cut flower production. The Netherlands is the chief supplier of the anthurium in the European market. Hawaii covers 60% export share of Japan and the rest of the west coast of the USA. The Caribbean produces the anthurium for the east coast of United States and Canada. Mauritius is one of the important producer of anthurium and it exports to Japan and Italy. While some eastern countries like Taiwan, Philippines, China and Thailand mainly produce for their local market. In India, anthurium is commercially grown in Kerala, Karnataka, Tamil Nadu, West Bengal, Maharashtra and north east India. Kerala is identified as the most desirable place for growing anthurium (Singh, 2006).

Alstroemeria belongs to the family Alstromeriaceae. Alstroemeria flowers third in terms of popularity and foreign exchange earnings in Kenya after roses and statice. Alstroemeria is named after a Swedish botanist “Baron Klas von Alstroemer”. The popularity of this flower is still growing in the global perspective. It is one of the quickest growing flowers with varying colours like purple, lavender, salmon, red, pink, white, orange, yellow and bicolour. It is grown for cut flowers but is also popular as a potted plant. It is grown in the higher ranges of the Western Ghats, Himachal Pradesh, Jammu & Kashmir and Karnataka in India.

ORIGIN AND DISTRIBUTION

The alstroemeria, sometimes called the Peruvian Lily, is native to Tropical America particularly Chile. There are some 30 species of alstroemeria that occurs in grasslands and Pampas of South America, Argentina, Bolivia, Brazil, Chile, Paraguay, Peru and Venezuela. In America, it flourishes in different climates from high in the Andes mountains to the deserts of Pacific coastline. Even deep into the tropics of Brazil, the plants flourish abundantly. It was introduced to Europe in 1753 when seeds were sent to Europe by Claus Alstroemeria of Sweden during his travels in South America. It was widely cultivated in England during the early 1800’s and it was John Hedgewood, the founder of the Horticultural Society who first introduced the white variety in 1832. Since then, the Alstroemeria has been hybridized extensively. It is named after a Swedish botanist, Baron Klas von Alstroemer, who brought the first seeds of A. oelegrina from South America to Europe. Columbia is the number one in the world as far as growing area of alstroemeria is concerned. The second and third positions are taken by the Netherlands and Japan respectively. Other producing countries are United Kingdom and Italy. Alstroemeria is a new introduction into the world floriculture scene.

Most commercial cultivars of alstroemeria are patented and protected through plant breeder’s rights. Because of the fact that quite a large number of new varieties and hybrids of alstroemeria are planted in various countries in each year, royalty is paid based upon their square footage under production or number of plants leased. The new Inca Collection bred by Konst Alstroemeria B.V. is a breakthrough in the presently dwarf alstroemeria assortment. The new extended range of alstroemeria cultivar offers the opportunity to grow these top quality perennials in the garden, pots and for cut flower. These dwarf type plants reaching a height from 20-50 cm, combine with the quality and colours of the long lasting flowers. New varieties have gained popularity in California (USA), New South Wales (Australia) and Spanish south east coastline, Sicily (Italy). However, for a very long time already alstroemeria has been cherished worldwide for its exotic flowers.

In India cultivation of alstroemeria has been started around Bengaluru, Pune and Hyderabad. It has been introduced in Palampur, Solan, Srinagar and hills of Uttrakhand and Ooty, to popularize this crop among growers for domestic and export markets (Singh, 2006).

Intellectual Property Rights (IPR) are legal rights, which result from intellectual activity in industrial, scientific, literary and artistic fields. These rights safeguard creators and other producers of intellectual goods and services by granting them certain time-limited rights to control their use. Protected IP rights like other property can be a matter of trade, which can be owned, sold or bought. These are intangible and non exhausted consumption. The term “intellectual property” denotes the specific legal rights which authors, inventors and other IP holders may hold and exercise and not the intellectual work itself (Chadha, 2013). Intellectual property rights are essentially territorial in nature so, where registration is necessary, for patents, registered designs and trademarks, these will not exist in other countries unless registration has been sought and obtained there.

IP protection is crucial for a sustainable contribution of plant breeding and seed supply. Breeding new varieties of plants, which are developed after contributing number of years to the selective inheritance of traits which provide improved yields, higher quality and better resistance to such plant varieties requires a substantial investment in terms of skill, labour, material and economic resources. However, a new variety once released could in many cases be readily reproduced by others so as to deprive its breeder of the opportunity to benefit adequately from the investment made. Thus, an effective system of plant variety protection (PVP) is a key enabler for investment in breeding and the development of new varieties of plants or improving existing plant varieties, encourage importation of foreign varieties, promote exportation of plant varieties provide access to information of the created products and the methodology of creation for the enhancement of social welfare and generally benefit the market place. An international system of IPR protection for plant varieties expands these benefits by facilitating access to new varieties created in other states (Gautam et al., 2012).

Intellectual property is usually divided into two branches: (i) industrial property and(ii) copyright and the rights which neighbour upon copyright. The principal categories of industrial property are: patents, trademarks, geographical indications, industrial designs and trade secrets. Industrial property according to the 1883 Paris Convention for the Protection of Industrial Property is to be understood in the broadest sense and to apply not only to industry and commerce proper but also to agricultural and extractive industries and to all manufactured or natural products including wines, grain, tobacco, leaf, fruit, cattle, minerals, mineral waters, beer, flowers and flour.

INTRODUCTION

Hybrid crops are derived from an established and well-proven breeding method used in ornamental sectors. The development of hybrid crops has been one of the major factors behind a dramatic increase in global crop yields. Hybrid is produced by crossing between two genetically dissimilar parents. Pollen from male parent called pollen parent will pollinate, fertilize and set seeds in female called seed parent to produce F₁ hybrid seeds. For production of a hybrid, crossing between two parents is important, the crossing process will results in heterosis or hybrid vigour. Heterosis is defined as the increase in size or vigour of a hybrid over its parent. This boost in performance, combining the best yield, quality and agronomic characters from each parent, is the result of hybrid breeding.

F₁ hybrid seed offers to the growers a significant benefits in terms of yield improvement, agronomic performance and consistency of end-use quality. But attempting to farm-save hybrid varieties will result in segregating populations producing highly variable offspring, which can lead to reduced yield, disease resistance and quality. As this factsheet explains, it doesn’t make economic or agronomic sense to save seed of an F₁ hybrid. In self pollinated crops it is difficult to cross but in cross pollinated crops it is easier. In nature to create genetic variability and for its wider adaptation in different environmental conditions, flowering plants has adopted many mechanisms for cross pollination. Cross pollination results in genetic heterogeneity and show wider adaptations. F₁ hybrids are in immense usage throughout the world with the rapid increasing interest in flowers, however the total number of the hybrids developed in flowers is still less. In India hybrid seed production is taken up in Bengaluru, Pune, Delhi, Punjab, Haryana, Jammu and Kashmir and Himachal Pradesh for export.

F₁ hybrids in ornamental crops were known even before Shull 1911 when he propounded the classical theory of hybrid vigour in plant breeding for the first time. In 1909 F₁ hybrid variety Prima Donna in begonia was released by Benary Seed Company in Germany. The first commercial F₁ hybrid in petunia was produced by Japan during World War II, in 1942. From 1950 onwards, F₁ hybrids were available in ornamental flowers from The Netherlands, Denmark, Germany, USA and UK besides Japan and produced in flower crops like ageratum, anemone, gerbera, primula, petunia, cyclamen, marigold, pansies, begonia, geranium, portulaca, dianthus, balsam, stock, wall flower, ornamental sunflower, gazania, hollyhock, calceolaria and zinnia. Flower breeders became familiar with the F₁ hybrid production of those crops also which were formerly propagated by vegetative parts such as pelargonium and gerbera. A few important hybrids were first released in petunia in 1940-50, geranium single in 1960, antirrhinum, marigold, pansy and zinnia in 1965, ageratum in 1966, geranium double in 1970, dianthus, impatiens, portulaca in 1976-77, gerbera in 1980 and carnation in 1981.

MOLECULAR BREEDING

Molecular breeding is the application of molecular biology tools, often in plant breeding.

Genetic markers

Genetic marker is defined as a gene whose phenotypic expression is usually easily discerned, used to identify an individual or a cell that carries it, or as a probe to mark a nucleus, chromosomes or locus (King and Stansfield, 1990). Three broad classes of genetic markers are morphological markers, biochemical markers and DNA or molecular markers.

(1) Morphological markers

Morphological markers are based on the visually assessable traits viz., morphological and agronomic traits. However, they are limited in number.

Features of morphological markers

i.They are easy to identify, there is no need of any complex analysis. Trait of interest can be identified visually.

ii.Morphological markers are inherited qualitatively or quantitatively.

iii.Frequency of availability of morphological markers is less in number i.e., morphological markers may not be available for all the traits of interest.

iv.They are influenced by environment.

v.Since they are influenced by environment, they are unstable in inheritance.

vi.They are stage specific i.e., a particular marker will be useful to identify in a particular stage of plant and not any stage of the plant.

vii.They are influenced by genotype and developmental stages of the plant.

Besides drawbacks, the morphological markers are useful to the plant breeders for the selection purpose in certain situation.

MUTATION BREEDING

Mutation refers to sudden heritable change in phenotype of an organism or permanent change in the number, kind and sequence of nucleotides in genetic material, while individuals showing these changes are known as mutants. Mutation was first discovered by Wright in 1791 in male lamb which had short legs. Hugo de vries coined the term mutation. In crop improvement the breeders are always look for wide range of variability and stabilization of desirable traits. Mutation breeding is very useful in inducing new variability, which is an essential requirement of any plant breeding programme. The modern day cultivars are the resultants of various breeding techniques like selection, hybridization, tissue culture and mutagenesis including some biotechnological tools. Novelty in commercial traits like colour, size, shape, length, post harvest life of flowers etc. are always valued and preferred by consumers. Mutation breeding by exposing planting material with irradiation has play vital role in inducing novelty in a number of flower crops.

TYPES OF MUTATION

Based on occurrence

(1)Spontaneous mutation: Occur spontaneously in nature and not present in sufficiently high frequency and spectrum.

(2)Induced mutation: Artificially produced by the treatment of various mutagenic agents and present in sufficiently high frequency and spectrum

INTRODUCTION

Various procedures which are used for genetic improvement of crop plants are known as breeding methods. The breeding approaches that are more commonly used for genetic improvement of crop plants are called conventional breeding methods. Following conventional breeding methods were followed in improvement of crops.

(A)Plant introduction

(B)Pureline selection

(C)Mass selection

(D)Progeny selection

(E)Synthetic and composite breeding

(F)Pedigree method

(G)Bulk method

(H)Backcross method

(I)Heterosis breeding

(J)Clonal selection

WORLD HISTORY

Work on ornamental crops was first initiated in Krelage Nursery founded by Ernst Heinrich Krelage for bulbs, lilium and dahlias in 1811. During 1895, Taiwan Agricultural Research Institute was established for ornamental crops. The first yellow corn Golden Bnatam was listed in Burpee’s Catalogue in 1902. In 1909 Primadonna F₁ hybrid variety of begonia was released by the Benary Seed Company in Germany and in the same year Atlee established seed farms at Floradale in California, Erfurt in Germany Anglia in UK and Kashmir valley in India for annual garden flowers. Luther Burbank did excellent breeding works on ornamental trees, flowers and fruits in 1926.

David developed the first successful hybrid in Nasturtium (1934) and Red and Gold hybrids of marigold (1937). In 1940, Burpee was successful in chromosome doubling and transformation of wild flowers and developed “Bright Scarlet” and “Super Tetra Series” in antirrhinum and “Jumbo Scarlet” in zinnia. He produced new strains of marigold, zinnia, nasturtium and snapdragon. William Houston in 1940 initiated the Ageratum breeding. Morden Research station was set up in Western Canada in 1945 for ornamental crop breeding. In 1968, Dr. Gustav A.L., Mehlquist was recognized as an international authority on breeding of ornamental plants. George J. Ball breeder of peas, asters and calendulas was a pioneer for the supply of dwarf impatiens and orange impatiens ‘Super Elfin’ in 1968. Israeli breeders during 1990 gave more attention towards the development of carnation, lily and anemone varieties. Longwood Gardens in 2008 got success in breeding of stock. The first record of chrysanthemum hybridization, germination and selection of superior seedlings occurred in 1827 by M. Bernet.

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).

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).

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.

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 d_i’ 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.

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.

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.

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.

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.