Wild Relatives Of Cultivated Plants In India

Wild Relatives of Cultivated Plants in India

K Pradheep D.C. Bhandari K.C. Bansal National Bureau of Plant Genetic Resources New Delhi

HIgS355I

ICAR

DIRECTORATE OF KNOWLEDGE MANAGEMENT IN AGRICULTURE Indian Council of Agricultural Research Krishi Anusandhan Bhavan I, Pusa New Delhi 110 012

Printed

:

July 2014

Dr Rameshwar Singh

Project Director

Dr Arana T. Kumar Shashi A. Verma

Incharge, English Editorial Unit Editor

Dr V.K. Bharti

Chief Production Officer Assistant Chief Technical Officer

Ashok Shastri

Š2014, All rights reserved Indian Council of Agricultural Research, New Delhi

ISBN

:

978-81-910388-8-0

Price

:

? 1,500

Disclaimer This book is mostly a compilation of information assembled on various aspects from a number of sources. Sincere efforts have been made to synthesize the reliable information with utmost care. However, neither authors nor the Indian Council of Agricultural Research can assume responsibility for the validity of all the information included.

Published by Dr Rameshwar Singh, Project Director, Directorate of Knowledge Management in Agriculture, Indian Council of Agricultural Research, Krishi Anusandhan Bhavan I, Pusa, New Delhi 110 012; Lasertypeset at Xpedite Computer Systems, 201 Patel House, B-ll, Ranj'.t Nagar Commercial Complex, New Delhi 110 008, and printed at M/s Chandu Press, D-97, Shakarpur, Delhi 110 092.

Contents

Preface

iii v

Acknowledgements

vii

Foreword

ix

Abbreviations

1 21 25 92 118 202 230 260

1. Introductory 2. Genus-wise information Abelia - Azadirachta Baccaurea - Byrsonima Caesalpinia - Cytisus Dacrydium - Dysphania Ecbolium - Excoecaria Fagopyrum - Furcraea Gaillardia - Gypsophila Haageocereus - Hyssopus Iberis - Ixora

271 287

309 320 327 331 351 387 394 409 467 468 487 535 559 560 573 575 575 576 582 725

Jacaranda — Justicia Kaempferia - Kydia Lablab - Lythrum Macadamia - Myxopyrum Nageia - Nyssa Ochlandra - Oxytenanthera Pachira - Pyrus Quassia - Quisqualis Ranunculus - Ruttya Sabal - Syzygium Tabebuia - Typhonium Ulex - Ursinia Vaccinium - Vriesea Wallichia - Wrightia Xanthosoma - Xylia Yucca - Yushania Zamia - Zoysia

References Family names index xi

1

V-

Introduction India is situated between 6°45' and 37°6' N latitude and 68°5r and 97°25' E longitude, covering an area of 3,287, 263 sq km with the coastal line running to c.7,500 km711. Out of more than 17,000 higher plants reported, one-third are endemic, mainly due to the lofty Himalayas in the north and encircling by sea on southwest, southern and southeast spreading over to 26 the three sides recognized endemic centres. About 2,500 endemic species are localized in the Eastern Himalaya (EH) and the adjacent regions, while 1,600 are in the Western Ghats (WG) and 200 are in the Andaman and Nicobar Islands (AN)711. Out of the top eight biodiversity hot-spots identified in the world, two are located in the Western Ghats-Sri Lanka and the Indo-Burma region1076. There are about 80 monogeneric families and approximately 266 unispecific genera occurring in India725. Predominance of Sino-Japanese flora has been observed in the Eastern Himalaya of European elements in the Western Himalaya (WH) and of African elements in the western parts and peninsular India (PI)711.

According to Maheshwari1075, about 40% of the Indian flowering plants are exotic, acclimatized and/or naturalized, and have become a part of the local flora.

It is mainly due to the landmass connections in the northwest and northeast, coupled with the intentional introduction for agriculture, forestry, etc. or unintentionally through human-delivery system. Plants of the latter category have come mainly from Tropical America, Australia and Africa. In the 20th century itself, more than 500 new records were reported725. This figure would go up further since most of the new records in the recent literature pertain to exotic-plants. There are also many economic plants native to one particular region of the country, and have diffused into other parts.

It is reported that about 14% of the higher plant species (c.35,000) are in cultivation to some degree in the world 2022. Although there is no comprehensive information on all the cultivated plants (CP) of India, it is estimated to be about 4,000 taxa. India is the homeland of 167 major crop species1043, i.e. the centre of origin/diversity (see section 1.2.). It is a common observation that the available germplasm-base of crops is not sufficient to meet ever-ending search for desirable attributes for future crop improvement. Here comes the role of wild relatives, which have been identified as the critical components for food security and environmental sustainability in the 21st century1038. Needless to say that understanding the proximity among the relatives and the CP is the lynchpin in realization of the above goal. In the light of contemporary biotechnological advances, most, if not all, species are the potential gene donors to crops1131, but in practical sense of conservation and utilization for food and agriculture, there will be no second thought on placing major emphasis on crop wild relatives.

It is obvious that each crop has had its wild parental relative(s)83’ 1033, which

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WILD RELATIVES OF CULTIVATED PLANTS IN INDIA

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3

INTRODUCTION

are too close in most of the cases, however, notably distant also in a few cases.

Whether these wild relatives of crops are traced out and their worthiness is exploited as is in the case of wheat, potato and tomato, or not even unraveled, thus creating a mental block in the thinking beyond the genus level, is a matter of great concern. It is always desirable to explore and utilize the related available species in the country rather than introducing material from outside, which is not as easy as it was earlier. Rise in number of threatened species indicate the importance of their conservation before they are extinct. This warrants the need for establishing crop wild relatives (CWR) inventories1038, which will be the first step to conserve wild relatives.

With the above ideas, this treatise is made for fulfilling the following needs. i. Updating knowledge of related taxa of cultivated plants of India, in general, and their native wild relatives (WR), in particular. Information is either lacking or fragmentary regarding species nomenclature, chromosome number, distribution, useful traits possessed, etc. ii. Prioritization of the related taxa to be collected, evaluated, conserved and utilized based on many criteria; since quite often plant genetic resource personnel focus on the taxon of the least interest, leaving important ones aside.

1.1 Plant classification: some aspects This section has been included keeping in view that some taxonomic issues like correct nomenclature, delimitation of species, revision of poorly circumscribed groups and polyploidy are of basic relevance for the study of wild relatives. Plant taxonomy is concerned with the identification, nomenclature and classification of plants, while systematics is involved in the determination of relationship of taxa. In classification, reproductive traits are given more weightage as all other characters are easily obliterated under cultivation'" 1077, while Sneath and Sokal1078 argued for objective and equal treatment of all the characters reproductive and vegetative as well. Numerous models have been proposed to explain species; of them, those of much relevance or appropriate to the subject like phenetic (morphological), biological (reproductive) and evolutionary (phylogenetic) species concepts are being briefly mentioned here.

Plant taxonomists are more inclined towards ‘phenetic species concept’ wherein prominent discontinuous morphological differences are the basis to be qualified as new species, although there is increasing interest among them to incorporate results from the cytogenetics and molecular biology. Various accidental features which vacillate depending upon the habitat factors, and vary from individual to individual such as hairiness are not to be considered the gist of the species556.

Polymorphic species (those possessing more accidental features) in literature are plenty, e.g. Dichanthium annulatum, Cenchrus ciliaris, etc. Mehra and Magoon reported 26 such species of forage importance in India. Nevertheless, it is not uncommon to see some polymorphic taxa split into many species, often referred to as biologically insignificant morphological variants extracted from a virtually continuous range of variation e.g. Taraxacum officinale, Rubus fruticosus. These morphological variants retain their ability to interbreed as differences in morphology may be controlled only by a few genes916. In many of the CP, morphological differentiation is in a quite advanced stage from its close WR but

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4

WILD RELATIVES OF CULTIVATED PLANTS IN INDIA

INTRODUCTION

their genetic incompatibility is weak927, e.g. Amaranthus hybridus vs A. hypochondriacus; Raphanus raphanistrum vs R. sativus; sugarcane vs its close relatives. The opposite is also evident in wild species (WS), i.e. there is a genetic barrier between types without an equally strong morphological separation; and therefore, taxonomists keep these types in the same species1088, 1089. The commonest cause is the different chromosome numbers (cytotypes) coupled often with external isolation mechanisms. Cross incompatibility was evident between rice races (indica and japonica) and some interclonal crosses of kiwifruit58.

In view of the above, there is a need to maintain appropriate balance. Stace1071 suggested that wherever morphological divergence of taxa is not markedly variable, breadth of the breeding unit becomes an important taxonomic character in its own right. Currently accepted hierarchy of classification by taxonomists is as follows: Family-Subfamily-Tribe-Subtribe-Genus-Subgenus-SectionSubsection-Series-Subseries-Species-Subspecies— Variety-Subvariety-FormSubform. It is not necessary that every rank has to be present in members of each family.

Biological species concept denotes species as groups of interbreeding populations that are reproductively isolated from other such groups1084. This concept works well with those organisms that reproduce sexually556, 1071. Many species phenetically defined coincide closely with that defined genetically478, 1071 e.g. Trifolium. Vida, Lathy rus, Medicago, Eryngium, Campanula, Allium1071, Picea, Pinus. Fraxinus, Acer191, although there are some exceptions within these genera. Taxon Group concept for finding out CWR proposed by Maxted et al.1072 (see section 1.4) may work satisfactorily with these groups. Biological species concept has got particular significance in the present compilation since it facilitates knowing of compatible parents for hybrid progenies1052. The problems concerned with both the above concepts have been discussed elaborately by Stace1071.

The phylogenetic species concept denotes that species is a single lineage of an ancestor-descendant population that maintains its identity from other such lineages, and has its own evolutionary tendencies and historical fate111 1080 [adopted from Wiley (1985)]. It is of immense value in identifying the progenitor and related species of crop-plants but has disadvantage that through this lineage affiliation can’t be unequivocally proven1080.

By considering merits of various concepts, many authors tried to define ‘species’. One such admired definition by Wagner470 is as follows. “a convenient taxonomic category that defines a unit of organismic diversity in a given time-frame and composed of individual organisms that resemble one other in all or most of their structural and functional characters, that reproduce true by any means, sexual or asexual, and constitute a distinct phylogenetic line that differs consistently and persistently from populations of other species in gaps in character state combinations including geographical, ecological, physiological, morphological, anatomical, cytological, chemical, and genetic, the character states of a number and kind ordinarily used for species discrimination in the same and related genera, and if partially or wholly sympatric and coexistent with related species in the same habitats, unable to cross or, if able to cross, able to maintain the special distinction”.

Till now, there has been no comprehensive system which can give an objective statement of degree of difference between two taxa to qualify for specific rank.

WILD RELATIVES OF CULTIVATED PLANTS IN INDIA

5

INTRODUCTION

As stated by Hancock916, nowadays, plant scientists are more willing to accept some degree of hybridization between otherwise distinct species.

At the infraspecific level, taxonomic procedures are quite perplexing. Some authors expressed that there is no necessity to split up variations while others favour division, reasoning voluminous work done in molecular biology, genetics and population biology on many species, hence, variations should be considered for discerning taxa. Moreover, delineating variation and naming it as a separate taxon, attention can be diverted to that taxon for conservation point of view; it can be rarest of rare1080. A number of infraspecific classification methods have been outlined, some of which are designed for special purposes, for example, classification of Vicia faba according to seed size and tendency of pod-

shattering1029.

The rank of ‘subspecies’ is used generally for geographically distinct and morphologically more or less distinct populations. Mayr and Ashlock1084 (p.430) defined it as “an aggregate of local populations of species inhabiting a geographic subdivision of range of species and differing taxonomically from other populations of the species”. Cytological variants with characteristic distribution patterns can be recognized by features rather than chromosome number alone to merit subspecies status1" 472. The term ‘ecotype’ is not recognized in the International Code of Botanical Nomenclature (ICBN) but is often used by many nontaxonomists as the one not isolated by genetic barrier, and is distinct because of thriving in an ecologically different environment. ‘Variety’ is usually applied to a morphological variant of a species, and in the words of Crowson1086, “it is a phenotypically distinguishable genetically determined variant”. ‘Form’ is for a minor genetic variant, controlled by small mutations or recombinations1080.

In India, majority of the taxonomists’ focus of work is on the collection of wild plants to preserve biodiversity. The cultivated plants are mostly ignored by them; and thus many of the economically important variations in them are almost lacking in the collections of traditional herbaria. This is a pointer for an urgent need to collect all the representative variations of the cultivated plants to reach to a meaningful conclusion on the classification of diversity existing within the cultivated plants. Till fifties, concept of microspecies was prevalent with cultivated plant taxonomists; now due to influence of cytogenetics, merging of such microspecies into broadly-based species is being favoured1024. Need of a hortotaxonomist to be conversant with classical taxonomy of CP together with WR and their origin is emphasized by Lawrence1087and Khoshoo927. In the recent years, use of molecular approach (phylogenetic construction using DNA sequences) for resolving taxonomic issues supersede over the traditional approach that uses gross morphology1056, and this is leading to lopsided growth profile of two major areas of systematics. Another major concern is the gap between the requirement and available qualified taxonomists in developing countries, like India, a hub of plant biodiversity.

1.2 Wild vs cultivated plants continuum Applied botanists sometimes indifferently use terms ‘wild’, ‘indigenous’, ‘native’, ‘exotic’, ‘alien’, ‘acclimatized’, ‘escape’, ‘naturalized’, ‘run wild’, ‘apparently wild’, ‘crop’, ‘cultivated’, ‘planted’, etc. These create a lot of confusion in proper description of a plant population with respect to habitat and usefulness 6

WILD RELATIVES OF CULTIVATED PLANTS IN INDIA

INTRODUCTION

to man. A clear understanding of these terms would help in correct documentation of the related species. The term ‘native’ or ‘indigenous’ indicates species that originate in a particular region, while ‘wild’ points out one occurring in a natural state or environment. So the species introduced long back (say >200 years) may have become a part of the wild flora but cannot be considered a native to the area, e.g. Solanum torvum.

Plant introduction indicates a genotype or a group of plants’ genotypes taken into new environments where they were not grown previously1090. It may be within the particular country (domestic exchange) or from foreign lands (exotic introduction). Though the word ‘alien’ means ‘exotic’, it is mainly used by the botanists in the context of naturalized/invasive weeds of foreign origin rather than cultivated ones. All the introduced plants may enter into series of steps in terms of degree of spread such as acclimatization-escaping-naturalizationinvasiveness. As a thumb rule, one out of ten species introduced will naturalize while one-tenth of the naturalized species may become invasive1”1785.

Acclimatization is the process by which plants are adjusted to a new climate or a condition, but have not yet escaped from human management. This may involve biological mechanism such as modification of structure and function during the pjiaoesK. Some also prefer to use the term ‘adapted’ in the above context. It should hr wdl-wJcrslDod that many of the introduced plants may not survive or enter llis ffirst) step. For the repeatedly introduced species that never become permanently established, the term ‘sporadically established’ is used. When a cultivated plant starts establishing its population in its vicinity without human effort, then it is called an ‘escape’ or ‘adventive’, e.g. Tropaeolum majus. It is worth noting that here the population is not yet naturalized. The word ‘colonization’ is sometimes arbitrarily used to represent gregarious nature of the plant populations without human efforts in a particular area. Naturalized species as per McNeely1 are “alien species that reproduce consistently and sustain populations over more than one life-cycle without direct human intervention (or in spite of human interventions); they often reproduce freely, and do not necessarily invade natural, semi-natural or human-made ecosystems”, e.g. Eruca vesicaria subsp. sativa, Tithonia diversifolia. The terms ‘run wild’ and ‘apparently wild’ also represent the same. Completely naturalized populations look similar to those of wild ones but do not have population structure. The extreme form of naturalization is invasiveness in which plant species encroach the ecosystem as well, e.g. Lantana camara and Eichhomia crassipes.

‘Weed’ is the wild/naturalized plant growing in disturbed areas, where it is considered as unwanted. Originally, the term ‘crop’ was implied to domesticated plants, but now is invariably used for all those plants that are cultivated. Hence the term ‘cultivated’ points to all plants, which are grown intentionally in manmade habitats, bred for a certain purpose (‘domesticated’) or may not be so This includes even those plants that are cultivated for soil improvement (greenmanure, cover-crop), sand-dune fixation (windbreak, shelterbelt), hedge, grafting stock, shade, support, etc. A plant may have been cultivated for multiple and changing reasons/purposes. The term ‘planted’ is used in the context of placing a young plant in a particular area for growing without much care e.g. forest plantations, afforestation, etc. In tribal and rural areas, a common practice of protecting or selectively maintaining wild plants is followed although they are WLD RELATIVES OF CULTIVATED PLANTS IN INDIA

7

INTRODUCTION

not planted intentionally, e.g. minor edibles, plants as rootstock for in-situ grafting.

In Harlan’s term, they are ‘encouraged’ wild plants1091.

It is evident that as the degree of domestication advances, there is a greater need for human-care. A fully domesticated plant is totally dependent on man’s intervention for survival. Hence, domestication is defined by Zeven and Zhukovsky1092 as the change of ideotype to adapt better to man-made environment.

In India, often the term ‘domestication’ is used in an informal way, that is after mere standardization of package of practices, especially in case of medicinal and ornamental plants. For more information on weed and crop, readers are advised to refer to Harlan’s ‘Crops and Man’1091.

Let us understand a little more about domestication since there has been increasing concern to domesticate promising WS in the rural areas, though it is not as simple as has been thought of. Plant domestication is a process rather than an event, involving number of evolutionary mechanisms mutation, hybridization, polyploidization, selection and genetic drift1014. According to Raamsdonk and Maesen1033, the relationship between the crop and the WR can vary from a simple process of crop domestication out of the genetic variation of a single WS to complex relationships between a crop and a range of weedy relatives and WR. Since morphological attributes are evolved at a greater speed in domesticated plants than the genetic barrier, most of the CP can still cross with the related

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taxa The word ‘cultigen’ represents a taxon with only cultivated representatives94, for instance, Triticum aestivum, Gossypium hirsutum, Nicotiana tabacum, N. rusticum, Brassica napus, Solanum tuberosum, Coffea arabica and Vicia faba.

Here no true wild forms are known, which indicate the role of two or more species.

According to Pickersgill1013, a crop may have been domesticated from plants similar to the modem weedy types and vice versa or the crop and the weed may have simultaneously originated from the shared wild ancestors. Even within a single crop species, wild progenitors have been repeatedly domesticated temporarily and spatially. It is generally acclaimed that introgression from diversified wild gene pool facilitates rapid built-up of variations in the domesticated

forms1027.

— rose, chrysanthemum, lily and orchids— interspecific

In flower-crops

hybridization1018, 1033 and polyploidy1018 are the major key factors in their domestication. Similarly, in fruit-crops, kiwi, citrus, strawberry, apple, Prunus spp., banana, pear, raspberry, blackberry and blueberry, they are responsible for domestication. For crops grown on a small scale or those reproducing vegetatively or have a long generation time, gene flow and disruptive selection are of lesser significance, probably artificial selection in them appears to be more intense1026.

Only a few wild plants have been domesticated lately (<300 years)—blueberries, Queensland nut, pecan nut, strawberry; and none of them can compete in their economic and commercial importance with the ancient domesticates. As already stated, there are many cultivated plants which are yet to be domesticated. In these, differences between them and their wild and weedy forms are often insignificant; these include many of the minor horticultural crops, most of ornamentals, fodder grasses, clovers and medicinal plants. Some scientific ways and means of fastening domestication process of Himalayan minor fruits have been suggested1097.

Coming to the relevance of WR with respect to crop-weed complexes as early 8

WILD RELATIVES OF CULTIVATED PLANTS IN INDIA

INTRODUCTION

_ I

1952, Anderson recognized and defined crop-weed complexes as “a impound of crops, accompanying weeds and wild-related species mutually iyfaencing each other by means of introgressionm 1033. Following some crops companion weedy races, barley, sorghum, rice, oat, carrot, Cannabis sativa, ebenopods and radish. Although this is not with majority of the crops, yet its

suspected consequence can be aggressive weeds and extinction of rare species1033.

E, The extreme form of this complex is ‘compilospecies’ , as has been stated by Harlan and de Wet, “genetically aggressive, highly polymorphic species, often of | complex hybrid origin, containing more than one ploidy level, often weedy and F; obscuring other species boundaries”in 94, e.g. Helianthus, Bothriochloa.

Indian gene centre is reported to have 167 economic crop species, and most of them have primary centre of diversity as India. In most of these crops wild forms/ progenitor/close WR exist within India. The number of cultivated crops is subject tochange whenever criteria fixed for categorization to be considered as cultivated change. There is an urgent need in compile data on native species cultivated in India to have complete itef nurra on the above category. Some crops recently hmngM malar irfaii u»n at India are: Saussurea costus. Inula racemosa and Ami tfmte is a confusion in pinpointing correct centre of dtaBOdlp' far mute amps* such as sesame, okra, etc. This emphasizes for greater :|”*™|||mwiiii r the systematics of native crop taxa, and elucidating "™ hips with wild species, evolution/domestication trends, tfcsir aamniinK' XUAI:

I

Ufa is a secondary centre of diversity for many of the crops that may have nrijpiamril especially from Africa and Middle East, due to peripheral distribution areas. some relatives of them have also been found to occur either in wild or in m cultivated form. In the case of ornamentals, the centre of diversity and centre of domestication are often different951 as is the case with the Himalayan natives, Rhododendron, Primula and Gentiana, which moved from Himalayas to Europe and the USA, where they have been domesticated as ornamentals. Certain crops like Rubus. Ribes, Rhododendron and Vaccinium which are not cultivated on a huge scale in India, though many wild relatives exist. In many foreign countries, they are cultivated in aplenty for commercial use, and their wild relatives have been exploited through and through.We need to think how in India we shall tap the potential of the Indian wild plants.

13 Natural and wide crosses: some considerations Natural hybridization has been defined as a successful mating in nature between individuals from two populations, or groups of populations, that are distinguishable on the basis of one or more heritable characters111 1096. Many plant species .retain their ability to hybridize with their relatives even when they are quite distinct.and fame strong reproductive isolation barriers?.?6. According to Grant84, piore fiÿp Hi* plant species descended from hybrids. He further mentioned that natural fatepecific, and in certain families, even intergeheric hybridization were of more frequent occurrence.

In nature, most Fj hybrids of cultivated and wild congeners were found in the process of acclimatizing to environs; initially the hybrid zones were very narrow ur adapted to very distinct habitat916, which can act as the nucleus for further OF CULTIVATED PLANTS IN INDIA

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9

INTRODUCTION

evolution of the hybrids1098. Spontaneous hybridization is frequently observed in cross-pollinated than self-pollinated crops778.

Hybrid-swarms referred often to a population of interspecific or inter-racial hybrids and their segregates and intercrossed derivatives (p. 265 of Radford et al.412) can be the first step in introgressive hybridization. Natural hybrid-swarms have been reported in fir, spruce, pine, eucalypt, birch, oak52, willow, rose1071 and also in poplar and blueberries54. In forest plants, these hybrid-swarms are known as ecotypes, akin to clinal variation52.

The implications of natural hybridization of worth reporting are as follows.

• Speciation through interspecific hybridization is an important mechanism in crop evolution1017* 1058. Hence, this will help in the study of ecology and in evolution of reproductive interactions, formation of weedy forms between closely related taxa.

•Occurrence of interspecific hybrids can sometimes be an evidence pointing out amalgamation of species, particularly when they have no distinct distributional, morphological or genetical set of characteristics from the parents1071 •Sometimes, hybridization between native and introduced species may lead to evolution of new invasive species916.

• Presence of hybrid-swarms indicates that artificial crosses by plant breeders would be comparatively easier.

Closeness of WR with crop-plants cannot be assessed soley on the basis of spontaneous hybridization. As is in the case of others, may be due to external isolation barriers geographic, ecologic, seasonal, temporal and mechanical— where no spontaneous hybridization occurs. Stace1071 concluded that reproductive isolation often reduces frequency of crossing rather than actual ability to cross.

Approximately, one-third of the flowering plants are polyploids, and around 70% of grass species are polyploids. Even most of the hybrid species are polyploids, and their world-wide estimation varies between 25 and 80% in 916 According to Mehra195, interspecific polyploidy is an important tool for formation of races, varieties and provenances in forest species. Polyploids have advantages over corresponding diploids in generously assimilating genes from other species as well as strongly tolerating abiotic stress owing to the presence of additional genomes. Besides, polyploidy widens range of plant distribution. According to Stebbins1099, quite often, taxa growing away from the centre of origin are polyploids. In wide crosses, ploidy often dictates crossability same ploidy level of both the parents ensures greater chances of crossing, e.g. Vaccinium, Malus and Prunus.Polyploidi zation coupled with interspecific hybridization is sometimes considered better in terms of economic use.

Historical work of development of many desired types in ornamentals was achieved through artificial wide hybridization by the nursery-men and professional plant-breeders when they had access to information related to hybrid-swarms, morphological and chromosomal similarity, ploidy level, species within the series/ section/subgenus/genus. With the changing scenario, biochemical and molecular tools can check on the hybridity. Extent of hybridization varies from species to species and up to inter-tribe level, researchers have developed hybrids. Following are some examples of various genera in different categories of wide crossing.

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WILD RELATIVES OF CULTIVATED PLANTS IN INDIA

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