Introduction
Plant exploration and germplasm collection
Priority regions and crops
Germplasm collecting: Logistics and tactics
Genepool sampling
Collecting wild relatives of crop species
Field data recording
Germplasm collecting strategies: salient points
Other considerations
Future emphasis/requirements
Summary
References
Appendix I (a). Passport data sheet used by the NBPGR, New Delhi (adapted from FAO/IBPGR form)
Appendix I (b). Example of general collecting form (Hawkes, 1983)
Appendix II. Field collection form recommended by the IBPGR and adapted for use in rice (IRRI-IBPGR, 1983)
Plant exploration is a fascinating field of study that has attracted a great many adventurists, naturalists, travellers and plant hunters since distant past. However, the golden age of plant exploration and collecting was the later part of eighteenth century when wider concern on plants of economic utility got generated with emphasis on their introduction. These activities picked up tremendous zeal at the Kew Garden sand some breath-taking adventurous voyages were undertaken with errands to collect specific materials such as bread fruit and the para rubber.
It is asserted that the post-Darwinian influence saw the understanding of variation in plant species and the science of plant breeding gradually generated interest and understanding of genetic diversity. But it was left to N.I. Vavilov and his coworkers (1926, 1951) to make us truly realise the value of crop plant diversity for genetic improvement needs. His concept on the centres of origin of crop plants and the diversity they hold has already been discussed in an earlier chapter wherein we have also briefly dealt with the concepts that developed later on the centres and non-centres (Harlan, 1975a), and on the nuclear centres (Hawkes, 1983). When linked with the species diversity, these regions hold the promising variation of potential plant resources.
In the Indian subcontinent, such activities gained momentum during the days of the British East India Company. A focal point of such endeavours was the then Royal Botanic Garden, Calcutta which was established in 1787. Special colonial interest led to hunting for tea in the Eastern Himalayas; growing of indigo, cinchona, mahagony, teak, jute, sugarcane and other crop plants. Surveys were also carried out in ornamental plants, particularly of the Himalayan region by Kingdon Ward and George Forrest revealing the enormous diversity such as in Primula, Potentilla and Rhododendron species, of interest to the Kew Gardens.
However, it was Sir J.D. Hooker who took the onerous task of working on the 'Flora of British India', which was brought out in 7 volumes during 1872-1897. Equally important, parallel to this, was the publication on economic plants/products of India (Watt, 1889-93) which dealt with their distribution, ecology and genetic diversity to some extent.
It is obvious thus that much plant wealth had been explored, collected and studied in the later part of the nineteenth century. The knowledge so gained formed the basis of further studies and in the middle of this century, much concern got generated to build up plant (genetic) diversity for use in crop improvement programmes (Mehra and Arora, 1982; Paroda and Arora, 1986). The search for new genes got initiated through the foresight of late Dr. B.P. Pal in 1940s and plant exploration, germplasm collection and introduction work was started. This received much attention at the Indian Agricultural Research Institute and later at the National Bureau of Plant Genetic Resources, where it is one of the major activities now. This aspect is dealt in detail under a separate chapter in this book. Equally important in this context was the continued stress on the study of floristic wealth by the Botanical Survey of India (BSI), Calcutta; National Botanical Research Institute (NBRI), Lucknow; and the Forest Research Institute (FRI), Dehradun during this period; the work having been carried out by these organisations as an on-going national activity. It was also during this period that a more specific activity, namely, plant genetic resources collection involving diverse genepools of crop plants and their wild relatives gained momentum for its utility/current use in crop improvement and its conservation for posterity. In this chapter, it is intended to cover a broad perspective of this discipline, which being field-based, involves considerable knowledge of geography, agro-ecology, plant taxonomy and biosystematics, ethnobotany, crop evolution and domestication, population variation/distribution/sampling and several other related fields. Since the primary emphasis in germplasm collecting is to capture or sample genetic diversity, techniques involved in exploration and germplasm collection, both practical and theoretical, logistic and tactics involved, and other significant points to be kept in mind while planning/undertaking exploration missions are discussed.
Plant genetic resources collecting
As is clear from the foregoing account, various institutes with different objectives are engaged in plant and/or germplasm collecting activities. It would be worthwhile considering the scope of the two activities, the similarities and differences and their complementarity taken together, viz. plant exploration as undertaken by BSI, NBRI, FRI, etc. as against the specific activity of crop germplasm collection. Plant exploration in its traditional sense is distinct from plant genetic resources (PGR) collection. This will be evident from the study/survey targets as specified/exemplified in Table 1. Thus, traditional plant exploration is complimentary to PGR collecting. The two aspects together help in locating more plant diversity of known and untapped potential of current and future use to mankind. Let us compare the two activities (Table 2).
Table 1. Plant exploration and collection vs. germplasm collection - Study targets based on traditional and current concepts
|
Plant exploration and collection (traditional) |
Germplasm collection (current/modern) |
|
1. Areas of floristic richness-biomes, vegetation/floristic
regions, formation, etc. |
Areas/regions of genetic diversity-primary, secondary centres;
specific attributes represented therein in relation to ecogeography/agro-ecology
|
|
2. Collection based on ecogeographic/phyto-geographic surveys;
more static/geographic approach |
As above; more dynamic geographic approach |
|
3. Floristics/flora of an area or region, etc. |
Crop resources - their distribution and diversity as per
utilisation, (cereals, pulses, fruits, vegetables, oilseeds, fibres, forages,
etc.) |
|
4. Monographic works on taxonomic groups/tax a |
Studies on crop domestication/evolution (including
archaeological, palaeobotanical evidences) |
|
5. Taxonomic diversity includes mainly species and supra-level
representation (taxonomic approach) |
Crop genepool including its wild relatives in one basic unit;
involves population structure, incompatibility barriers etc., crop germplasm
includes landraces, primitive cultivars, introgressed forms, obsolete and
promising plant genetic resources (genetic approach). |
|
6. Economic taxa-synthesis on basis of uses; ethnobotanical
information, collection of wild ornamental plants, study of potential elements
of flora |
Utilisation linked with agro-botanical/agronomic
attributes-plant type, promising traits etc., landrace (s) diversity also linked
with ethnic diversity/anthropogenic factors |
|
Plant species collection |
Germplasm collection |
|
1. Wide range of species collected and all ecogeographic
regions surveyed for collection |
Narrow range of taxa-crop and wild plants collected;
collection done in agro-ecological zones/areas with different agricultural
practices |
|
2. Specific and supra-specific categories represented
|
Material collected mainly at infra-specific levels |
|
3. Variation represented in commonly available plants and
extreme variants, either end of range of variation, is represented (cultivated
taxa represented are an extreme type of variation) |
Within the unit of collection/genepool, full range of
variation represented - common types through random collection and rare types
through biased collection |
|
4. Functional unit of study/collection is species, largely
characterized by differences in morphological traits and geographic distribution
|
Functional unit is a population and unit of demarcation is
barrier to geneflow |
|
5. Collection for flowering/fruiting materials, i.e., limited
range of variation represented |
Collection surveys taken up based on life cycle pattern - seed
producing, vegetatively propagated, annuals/perennials etc. |
|
6. Periodic surveys of area through the year for full
representation of material |
Repeated surveys in season of occurrence/maturity for full
representation of variability |
|
7. Data recorded on limited scale-habitat, locality, size,
colour, of plant/plant parts, uses, etc. |
Exhaustive data recording done-site/habitat, habit, other
characteristics etc. (refer Appendices I and II) |
|
8. Material collected and preserved as dried, mounted and
identified specimens in Herbarium; in live state, species represented in botanic
gardens; phenological data recorded |
Material collected as seed, pollen, embryos, vegetative tissue
for multiplication/conservation; live material represented in field
genebank/plots; regrown material used for evaluation |
The collecting of plant genetic resources primarily aims at tapping germplasm variability in different agri-horticultural (crop) plants, their wild relatives and related species. The germplasm so collected reveals the nature and extent of variability in different species, within species, cultigens, etc. as also their agro-ecological/phyto-geographical distribution. As clarified above, such explorations differ from the floristic surveys which are mainly undertaken to study the flora or plants of an area or its vegetation so as to list out the species diversity. Such botanical studies are generally of taxonomic and ecological relevance and do not deal with the genetic diversity concepts, whereas the botanical collector may look for uniformity or trueness to type. The field sampling procedures in plant genetic resources exploration are aimed at the fullest possible recovery of genetic variation within species, irrespective of the relative frequency or rarity of any genes. Thus, exploration and collection of plant genetic resources must be based on the application of sound scientific principles. The objectives of the botanical collector and the plant genetic resources collector are not the same. Hence, more meticulous planning is required in dealing with germplasm collecting so that the explorer is in the right area at the right time and can search for and collect germplasm - ripe seeds, tubers, vegetative propagules, etc. and study the existing variability in the field. Knowledge of agro-ecology, crops and their distribution and harvesting time in areas of survey, local contacts, equipment required, transport arrangements and routes to be followed, distances involved, places of halt/camping sites available, transport of material, besides team-composition etc. is to be acquired before setting out on a collecting expedition. Of equal importance is to acquire knowledge on diversity in crop plants vis-a-vis its distribution to tap target areas and/or target species and the variability contained thereof.
By and large, germplasm collecting missions are broadly of two kinds:
Specific missions
The aim is: (i) to collect variability in a particular crop or cultigen, or material of specific attributes, say wheat, rice or maize; e.g. types adaptable to saline tracts -durum wheat in western Indian plains; cold tolerant forms in maize and rice, i.e., in high altitude Himalayan ranges at 2000 m and above; (ii) to collect specific wild relatives, weedy types and related taxa of agri-horticultural relevance e.g. Saccharum, Solanum, Abelmoschus, Oryza, Mangifera, Citrus, Musa and others.
Broadbased missions
The aim is to tap maximum diversity in different crops (multi-crop collecting missions) occurring in the region to be explored, and maturing almost at the same time like maize, sorghum, pearl millet, rice, cowpea and mung bean during kharif (June/July - September/November); and wheat, barley, Brassicae, gram, peas and French bean during rabi season (October - March).
Invariably, genetic resources organisations undertake both kinds of explorations depending on the priorities assigned to crops/regions, specific needs of the breeders to enrich germplasm variability with desired attributes, and to salvage endangered/endemic resources, landraces, wild types, etc.
Emphasis by germplasm collecting missions is thus laid on an understanding of prevalent genetic diversity in different areas/crops and the field tactics involved. The prevalent diversity at specific, infra-specific and genepool level, considering the variation available in diverse populations/different kinds of genetic resources, would fall in the following germplasm categories (Frankel and Soulé, 1981; Hawkes, 1983):
1. Landraces/primitive cultivars;The relative importance of all these kinds of genetic resources, also including breeding lines and genetic stocks, cannot be undermined though first four categories would demand prioritisation in national context in germplasm collecting. A still wider spectrum including the above PGR categories as expressed by Chang (1985) has already been discussed briefly in an earlier chapter and exhibited here in Figs. 1 and 2. By and large, it is necessary to acquire knowledge on the spectrum of genetic diversity occurring in the centre of diversity of a crop and in the areas of its cultivation (Williams, 1978).
2. Wild and weedy relatives of domesticated species;
3. Wild species used by man;
4. Wild species of potential use to man; and
5. Obsolete and advanced cultivars.
In view of the above prioritisation on the kinds of germplasm resources to be captured, national emphasis primarily by the NBPGR in the last one decade or so, has been on collecting of crop diversity in specific areas, which are genetically rich in economic plant wealth, such as the northeastern, western Himalayan and the peninsular regions. Apart from these, equal emphasis has also been laid on crop priorities as identified in the IBPGR Workshop on the South Asian Plant Genetic Resources organised by ICAR/NBPGR in 1978 in New Delhi and in 1982 in Kathmandu, Nepal. These priorities kept in view national/breeders' need for immediate crop improvement programmes, gaps in existing collections and the threat to genetic diversity in natural habitats. Details are given in Table 3 (Arora, 1988).
Fig. 1. Generalised spectrum of germplasm in a crop species (Williams, 1978)
Fig. 2. Different categories/types of genetic resources (Arora, Nayar and Pandey, 1990)
Table 3. Crop collecting priorities in national context (Arora, 1988)
|
High |
|
Low |
|
A |
B |
C |
|
Wheat, rice |
Maize, barley |
- |
|
Sorghum, finger millet, pearl millet |
Prosomillet & others |
Amaranth, buckwheat |
|
Chickpea, pigeonpea, Vigna (Asiatic) |
Lentil |
Soybean, winged bean, rice bean |
|
Groundnut, sesame, Brassicae |
Safflower |
Niger |
|
Cotton |
Jute |
Kenaf/mesta |
|
Citrus, banana |
Mango, jackfruit, egg plant, okra, cucurbits, tuber crops
|
- |
|
Coconut, sugarcane |
Tea, arecanut, turmeric, |
Ginger |
|
|
medicinal plants |
|
Technical aspects
Logistic preparation/Implementation
Practical guidelines
Germplasm collecting involves application of both the theoretical knowledge on population sampling and practical knowhow in overall understanding of plant diversity and environment including the socio-economic and cultural aspects of the farming societies. Tactics, logistics, preparations and procedures have been elaborately dealt with by Bennett (1970), Harlan (1975b), Hawkes (1976, 1980), Arora (1981a) and Chang (1985).
Exploration planning involves prior knowledge of the area, its people (cultural communities, ethnic groups), socio-religious customs, eco-edaphic conditions, crops grown and the varietal diversity available. Before embarking on an expedition, an explorer must synthesize all available information which would guide him:
1. in deciding the route of expedition and sites for collecting;Further, soundness of the political climate of the terrain to be explored is also of primary concern while planning germplasm collecting missions. All these aspects are broadly dealt with here.2. on the strategy of genepool sampling to be followed; and
3. about the equipment to be carried for collecting and transport of material; apart from certain other miscellaneous pre-requisites.
Acquiring knowledge on agro-ecology and crop/plant distribution
It would be necessary to acquire knowledge on the agro-climatic conditions in relation to the distribution of species/varieties/taxa of crop(s) and/or their wild relatives in the area to be explored. In this context, state reports, regional documents, floras, floristic surveys and other published works would help a great deal to familiarize the plant explorer with the climate, ecology, vegetation and agriculture. More emphasis should be laid on latest published/unpublished reports of the plant explorers/surveys carried out. Such literature would provide clues to the harvesting time of the crops, prevalent agri-horticultural diversity and the economic plants available in relation to agro-ecology of the terrain. Local habitat variations within an agro-ecological region are often enormous and ecotypic variation correspondingly great.
Use of a herbarium in plant genetic resources collecting
Herbarium studies offer a quick approach to get familiarity with the flora/plants of an area through comparative study of apparent species differences. Depending on the explorer's mission, this study is very useful and of great utility in locating desired types. Since the collections of species in a herbarium are from different regions, the herbarium specimens provide information on the phyto-geographic/ecological/eco-climatic range of species, and suggest specific areas for collecting more material.
Particularly, in national herbaria holding large collections, the explorer can chart out the distribution of species based on herbarium field notes. Flowering and fruiting variation (through dates of collection listed in field notes) at different sites by study of herbarium sheets can help the explorer to plan properly the itinerary of the exploration team(s).
Herbarium studies are particularly useful in locating/collecting species with a narrow range of distribution, endemic cultigens/wild taxa (Oryza, Moghania, Digitaria, Piper, Abelmoschus). The explorer gets useful pin-pointed information from herbarium sheets as to earlier sites of collection and can thus hunt for more material from such sites. Also, over a gap of time, survey of such endemic locations helps in the study of differences in the nature and extent of variability and the increase or shrinkage in distributional stretch of such types vis-a-vis their ecological/climatic adaptability. In the natural distributional range of species, wherein wild forms and native domesticates occur, herbarium collections would offer excellent material for comparative study. Thus, before embarking on a programme to enrich variability in endemic cultigens, the explorer must study the specimens thoroughly to develop an insight into crop evolutionary concepts/biosystematics.
Herbarium notes of plant collectors/explorers/botanists provide new or additional information on the utility of various plants, particularly when such a collection is from areas (under-explored pockets of vegetation) where tribals or native communities live and practise subsistence agriculture; such natives gather wild foods and even depend on such wild wealth to cure their ailments. Such uses vary from one ethnic group to another and diverse herbarium collections provide such information. Even different uses of the same plant part may also be there. In the Central National Herbarium, Howrah (India), retrieval of such information has yielded useful data on Solarium, Piper and others. In this context, assembling of such information from a regional herbarium should be of great advantage and with this prior knowledge, plant explorer's collecting would certainly become more rewarding.
The herbarium provides basic material for detailed monographic/phyto-geographical studies. The explorer may get involved in such work on economic plant taxa (Vigna, Saccharum, Abelmoschus, Oryza, Piper, Solarium, Morus and others), and in such cases, before he undertakes the taxonomic revision, study of earlier collected herbarium materials would point out to the lacunae/gaps and help him to plan his explorations to enrich representative and diverse material. Since the type or related material (material on which the name of the taxon was based and the species described) is available, disputes about taxonomic validity can also be solved. Such collections, when studied in detail, point out to the taxonomic limits of species, intraspecific taxa and other variants. Helpful clues to correct nomenclature are also provided. More details on the use of herbarium studies in plant genetic resources collection have been dealt with elsewhere (Arora, 1981b) and may be referred as per the needs of the collecting mission.
Visit to genetic resources centres
It would be desirable for an explorer to plan a visit to the genetic resources centre or institute/other crop-based institute of relevance to his mission. If planned in the crop season, he can see (part of) the collections in the field. At least, the resident/country collectors) must get familiarity with such collections. When the collector is directed to collect specific materials possessing specific attributes, discussions with crop breeders/botanists maintaining and evaluating local/regional/national collections provide useful clues to the areas of survey. Published articles and catalogues on crops also provide such useful information.
Establishing local contacts
It is necessary to list out the local agencies and/or centres in the area of survey and establish administrative/scientific contacts, such as with State Agricultural Departments, Block Development Offices and their branches, and Regional/National Institutes. Information on the locations proposed to be visited, routes to be followed, position regarding camping sites, distances between places en-route (jeepable or to be covered on foot), location of petrol pumps, crops and their harvesting time should be discussed with local counterpart(s) before embarking on the mission. Also, it would be better to develop contacts with scientists engaged in crop specific research programmes, and to correspond with local contacts in order to know more about the nature of variability available in native genetic resources - landraces and their distribution, occurrence of wild species, etc.
Planning of itinerary
Information collected as above would help in the planning of proper itinerary. A provisional route and time schedule can be worked out based on the harvesting time, agro-ecology of the terrain and the distribution of crop diversity, wild relatives, endemic types and accessibility to the area, etc.
When explorations are planned in foreign countries, all arrangements including transport, etc. must be finalized well ahead of time through national/regional/international contacts locally available. Besides, it is necessary to carry with you a permission letter of your Government/institute, letters of contact containing previous correspondence, permit to visit distant areas otherwise out-of-bounds; when from a foreign country, visa, inoculation, health certificate, passport, etc. must be carried. As per phytosanitary regulations, if despatch of the collected material is required to be done, carry the authority from home country and get it processed through national quarantine service in the country being visited.
Larger teams usually prove cumbersome while small teams are more effective and mobile. A two-member team is considered ideal with a local helper, crop specialist/extension worker. One-member (man) explorations have been effective in the past with local guides employed from the area of survey. Since the native and/or primitive plant types occur in areas usually dominated by tribals (native communities), larger teams create suspicion, while smaller teams are welcomed and can build up confidence quickly through the local officer/guide. The farmers of underdeveloped tracts holding native landraces do not like or permit visit to their fields, and the smaller the party, lesser the interference and more the possibility to survey such sites. When the crops have been harvested and are in the threshing yard or lying in the hutments of the dwellers, movement of larger teams interferes in the privacy of the natives, while one or two member-team with a local helper gets usually attended to properly and is able to collect the desired germplasm. In some specific exploration missions, larger teams are unavoidable. Here, the mission would have a crop scientist/plant pathologist and it is an additional advantage if one such member knows driving also.
Team composition
When the team has more members, the leader must coordinate collecting activities right from the initial planning. Sometimes, team members are from different centres/organisations and an effective contact is to be maintained with them by the team-leader. Before the collecting programme starts, the leader must thoroughly brief the party members in the first meeting.
Duration of exploration
This would vary according to the mission. Explorations within the country are of shorter duration; 4 weeks or even less would be ideal, but when organised in foreign countries, longer duration (more than one month) is normally recommended, as otherwise exploration missions tend to be more expensive and less purposeful. However, no hard line can be drawn as this would depend much on the area of visit, crops involved, mission's needs, the harvesting time, etc. If a larger ecological range is involved (altitudinal/latitudinal variation), collecting season is prolonged and 2-3 months may be needed to cover diverse terrains. Variation in sowing dates is related to weather conditions, topography etc. For every 1000 m in hills, the temperature falls by 5° C, slowing vegetative growth and delaying maturity by 2-3 weeks. Since reconvassing missions in foreign land may not be normally feasible, long duration explorations are considered more practical.
Basic field exploration equipments
The more important items and equipments required are:
|
Survey/collecting items |
: a) altimeter (with adequate altitudinal range), compass,
soil kit, SLR camera (35 mm), binoculars, hand-lens. |
|
|
: b) Haversack/kitbag, seed envelopes, cloth bags, alk-athene
bags, tag lebels, drying sheets, old newspaper, plant press, vasculum, rubber
bands, gum tape, rope (thick and thin), alkathene sheets, scissors, knife,
trowel, digger; and for field data recording: field note book, collecting
sheets, diary, pencil, ball pen, red/blue pencil/marker, stapler. |
|
Published material |
: Regional flora, other reports, list of local names of
crop-plants/cultivars; road-map, vegetation/climate map, list of
rest-houses/lodges, hotels, resting/stay places, petrol points (diesel, petrol),
distances between sites/towns en-route, jeepable tracts, fair weather roads,
etc. |
|
Medicines etc. |
: Anti-malaria pills, APC tablets, anti-amoebic and
anti-diarrhoeal tablets, Vicks, Odomos, Burnol, antiseptic cream/Savlon/Dettol,
cotton-packs, Johnson band-aid, Furacin powder, dressing gauze, water-purifying
tablets, first-aid box. |
|
Other equipment |
: Water bottle, torch (with extra battery cells), large
candles, match boxes, steel box, card-board/carton boxes or other containers,
printed slips with the Institute's address, plastic jars, formaldehyde, alcohol,
hunter shoes, tarpaulin, camp-cots, sleeping-bags and other camping, cooking
items depending on need, cap for sun protection, etc. |
Having acquired the basic knowledge on the aspects of sampling, practical considerations would demand application of certain other tactics, as discussed below:
Survey tactics
Some practical suggestions are discussed below:
1. Depending on the area of survey, the explorer should cover drier sites earlier and the humid belts later. Likewise, unirrigated pockets holding primitive germplasm would need survey much ahead of that to be conducted in the irrigated terrain. Also, in the hills, normally lower valleys need to be covered earlier than the higher elevated areas, barring special ecological situations such as cold arid desert in the Western Himalayas.The areas holding landraces are invariably dominated by native people who eke out marginal existence based on multi-crop subsistence agriculture practised on small land holdings. Often it is observed that the natives consume the previous year's harvest. So, only limited/meagre collection will be possible when exploration is organised in such areas during seasons other than the crop maturity period. In such situations, the plant explorer should stress on collecting from the previous year's harvest and take care not to collect infested seeds.2. Where the mandate of the exploration team is to locate types specifically adapted to particular environments/sites, which vary in soil, climate, topography/elevation, visualize climatic variation vis-a-vis itinerary properly so as to collect specific types suited to such edaphic ecological situations, physiologically stress situations (saline habitat, grown under unirrigated condition/drought adaptable and cold adaptable). It is advantageous to collect germplasm in sites/villages much away from the approachable roads, as the easily accessible sites must have been previously explored. Collection must be planned in inaccessible pockets-valley and isolated hills, difficult to approach even on foot. Situations representing limits of agriculture, namely, altitudinal limits of agriculture in mountains or deserts may offer different germplasm. Likewise, villages at the edge of the desert, isolated coastal belts (islands) and the ecotonal belts in case of wild germplasm would present more exacting sites of potential diversity.
The collector must keep in mind that crops often vary with ethnic diversity and different array of materials may be collected even from contiguous belts occupied by different tribes. The explorer should survey such sites/villages very thoroughly, as invariably such locations are rich in materials in which endemic characters are numerous. Here, the village (tribal) chief is a very important contact person. Local guide, or interpreter accompanying the party can bridge the gap and create goodwill and confidence. Further, it is advocated that in such remote survey areas, the team may take token gifts for the natives. Occasionally, some token money may have to be paid to these farmers to get their harvested produce so as to collect the desired germplasm. But this must be negotiated first through local counterpart/guide and implemented only when permitted by the village chief, who would be then the first one to receive such gift items.
Transportation of material
If the team is to send plant/germplasm collections to the institute, halting in-between at a bigger town may be necessary. Incidently, this halt can also be utilised for re-equiping provisions, jeep servicing/checkup and purchase of several other articles needed by the team. For long duration explorations in other countries, transportation of collections to destination would be required and halts at towns with air-transport post-despatch facility, etc. is advocated, though as per pre-arrangement, normally collections would need phytosanitary clearance from the authorised agency in that country.
Funding aspect
Exploration funding is always tentatively worked out. The team occasionally may find this calculation as an under-estimate. Additional funds may be required. So, keeping track of accounts is essential and the team-leader is to be vigilant about fund position. If more funding is needed, take action much ahead of time using facsimile, telex, telephone or cable - a quick message delivering facility through the local Government. One has to pre-plan this action so that the work is not held up. In general, include unforeseen expenses while estimating funding of expeditions. Keep enough local currency for use during exploration - en route travel in small towns, money of smaller denominations and coins for village transactions.
After expedition care
Follow up would be needed so that the accessions collected are kept safe, indexing/accessioning may be done and collections passed on for quarantine. Be sure that the field books, and survey/field notes are complete for writing the final report. The use of a portable computer containing the collecting sheet format is becoming more and more common practice and can be a considerable time-saver.
Sampling strategy
Sampling frequency and size
Collecting sites/sources
The sampling strategy largely depends on the crop species (self or cross-pollinated or vegetatively propagated) and the extent of gene exchange between populations; as also on the primary objectives of collecting the genetic diversity in the area being covered.
Though the theory of sampling strategy stresses upon extensive knowledge of the patterns of genetic variability of populations, in general, there are relatively few species for which this type of information is available. Most species exhibit extensive geographical variation and superimposed on this is the variation within populations. Ecological habitat and/or factors are a major determinant of genetic diversity, and agro-ecotypes are most clearly distinguished in primitive cultivars and landraces. Climatic factors, such as maximum and minimum average temperatures, precipitation and the seasons of dormancy and growth, light intensity, and day length are all reflected in corresponding developmental characteristics (Bennett, 1970). Such factors generally lead to clinal variation patterns, whereas topographically or edaphically determined differentiation may lead to either a clinal (as in the case of altitude) or a mosaic distribution. Consequently, the distribution of variation as affected by such factors should be reflected in the frequency of sampling.
It is also realised that geographical variation patterns include such characteristics as disease resistance, morphological features and other conspicuous differences as well as variation in quantitative characters relevant to plant breeders. Though varieties or strains may look alike, they would differ greatly in useful attributes, especially in physiological characters. The variation within populations, especially at the local level, will depend on the interaction of the breeding system of the species and the forces by which variation is maintained, the maintenance of heterozygosity in outbreeding species and genetic structure of inbreeding species. There is now a considerable evidence which shows that such populations also contain much genetic variation and heterozygosity. Sampling methods must be used to ensure the collection of representative within-population variation as well as that associated with geographical patterns of variation.
The principles in selecting the site (field) and sample numbers in relation to genetic diversity have been discussed by Marshall and Brown (1975), Hawkes (1980), Chang (1985), and several other workers, but are to be used with a great deal of practical approach. For sampling of a general nature, random collecting at pre-determined intervals will be satisfactory. The intervals can be wide in an ecologically/edaphically uniform environment or site and proportionately small when the collecting sites include much faster changes in topography/altitude, soil types, farming practices or such other features as observed in an agro-ecologically diverse environment.
For sampling of a specific nature or re-sampling on a more intensive scale or collecting of wild relatives of the cultigen, sampling should be carried out over more specific sites in the same area. Here, attention should be directed to the identification of special types such as pest or drought-resistant cultivars. For wild relatives or weedy taxa, collect selectively from populations which are bordering or located inside cultivated fields. Also, collect from populations occurring in distinct eco-edaphic niches (Chang, 1985) and natural habitats.
The general principle in sampling is to randomly collect a bulk sample from the site by harvesting randomly panicles or fruits of a number of plants from several spots in the site. The collector may walk across a site or a field twice - in the form of a cross or zigzag manner avoiding sampling from the borders. This procedure of coarse grid sampling will sample the maximum variation in the population if the site is large and contains distinct differences in eco-edaphic conditions. In the other method, called the clustered sampling pattern, one collects several samples within a small area and repeats the sampling over several areas within the broad-based site. This clustered pattern allows the inclusion of large variability related to both geographic and microgeographic differences in environment. It may be better suited for wild or weedy forms. In hot spot areas, the collector should collect healthy looking plants in fields where severe disease or insect damage is evident. Also, in an environmentally stress prone area (drought, cold temperate or related to adverse soil), such selective collecting is required and may yield unusually promising genotypes.
The frequency of sampling (number of samples per site) and the size of each sample would be governed much by the extent of genetic diversity and geneflow within a taxon (cultigen or wild form) and the agro-ecology of the site. The collector should use a practical approach and utilise the on-the-spot observations to devise the best sampling technique. The optimum sample size per site would be the number of plants required to obtain, with 95 percent certainty, all the alleles at a random locus occurring in the target population with frequency greater than 0.05 (Hawkes, 1976; Marshall and Brown, 1975). Hawkes (1980) has pointed out that, about 50 seeds per head, ensuring a total of 2,500 to 5,000 seeds, are collected in each sample, particularly in highly variable crops. If the plant species in question produces small pods with limited number of seeds in them, standardise by taking five or more ripe pods from each of three adjacent plants every three paces so as to make up the total of 50 seeds. If the species produces inflorescences, spikes, etc. with very large number of seeds (such as in sorghum and millets with 2,000-4,000 or more grains), only parts of each head need sampling so as to provide the 50 seeds required. When sampling maize, it is advisable to take one ear every 10 or 20 paces, according to the size of the field, separating the transects by about 5 to 10 rows. The sampling of crops with seeds in juicy berries or other types of soft fruits (tomato, pepper, cucurbits, etc.) is basically similar. If each berry contains about 50 seeds, about 50 to 100 of these should be collected at random and put together as a single sample. Fruits with fewer seeds should be sampled in larger numbers in order to make up the required number of 2,500 to 5,000 seeds per sample. In some instances, it may not be possible to collect more than 100 to 1,000 seeds. Such small numbers should also be collected or even less, if they are all that can be found. For extremely small seeds, such as clover (Trifolium) and poppy (Papaver), very much larger samples should be collected, since samples of small size are very difficult to handle in practice. Wherever possible, seeds should be collected from plants that are disease-free or undamaged by pests. Not all the seeds in the head or fruits may be mature and allowance may have to be made for conditions of low seed set or low seed viability. Where this is suspected, a larger sample than usual would be advisable.
Where some populations seem to be extremely variable, one can either make much larger samples, or take several distinct samples from various parts. Non-random collections based on 'race identification' can be made in addition, but should be given distinct collection numbers and kept separate from the random collection. Additional non-random (or selective) samples may be added as sub-samples if the collector sees any particularly interesting variant present in small numbers, which were not included in the sample by strictly random sampling. Some authorities advise that non-random samples should not be mixed with random ones but should be kept separate and given another collecting number. In general, more sites per target area is preferred to more seeds per site. The suggestions in Table 4 may be helpful (Chang, 1985). The collector thus should use his own judgement in choosing an efficient size to meet his objective and to suit his capability, especially when the collecting trip covers a large area and is planned for a relatively longer period or when erratically distributed crops like fruit tree species, and root and tubers are collected. The ease in carrying the samples, and in adequately drying and packing them during travel may become an overriding factor. Invariably, 200-250 g/sample yields enough seeds/accession, but 500 g may be needed in larger seeded crops (beans and groundnut) and much less (50-100 g) in small seeded types, such as tobacco, sesame, Brassicae, tomato and Amaranth. If the collected samples will go directly into medium or long-term storage without seed increase and observation, larger sample sizes are needed.
Table 4. Sampling of populations during field collecting (Chang, 1985)
|
Type of population |
Site/day |
Plants (panicles)/site |
|
Slightly improved |
20-40 |
15-30 |
|
Unimproved (primitive) |
10-20 |
30-50 |
|
Wild-growing |
10-15 |
40-60 |
|
Outbreeding |
10-15 |
30-60 |
Four main collecting sites can be recognised, namely, (i) farmer's fields; (ii) kitchen or orchard gardens; (iii) markets; and (iv) wild habitats (Hawkes, 1980). Most important, however, is collection from the farmers fields which provides visual realisation of the much required wealth of landraces and primitive cultivars of the main food/other crops. Much would depend on the location and size of farmers' land holding. Subsistence farming sites are ideal for sampling rich diversity of crops, grown in kitchen gardens/orchards for small scale markets. The choice would thus be site-dependent. Also, the farmers stores provide useful variability from the previous year's harvest.
As compared to the collecting efforts made in augmenting genetic diversity in cultivated plants as reflected above, relatively much less emphasis has been placed so far on the wild relatives of crops plants. This category of diversity is required to further enlarge the genetic base available to the breeders for crop improvement.
By and large, wild relatives and related taxa, using the terminology of Harlan and de Wet (1971), can be classified into primary, secondary and tertiary genepools (Harlan, 1975a). Wild species in the primary genepool can produce fertile hybrids with cultivated types but those in the secondary genepool contribute germplasm less easily. The tertiary genepool can only be used for some crops for a limited number of genetic traits. This has been well defined and emphasised by Harlan (1976, 1987). The wild species and the weed races represent the highest level of genetic heterozygosity and heterogeneity among the different classes of germplasm. They generally have higher rates of natural outcrossing than the domesticates. Oryza longistaminata, a perennial wild rice of Africa, is even self-incompatible.
The genetic variability provided by the wild species and weed races is a source of:(i) resistance to diseases and insects, controlled mainly by major genes; (ii) tolerance for extreme environments such as salinity, desiccation, waterlogging, and frost; (iii) high vegetative vigour in sugarcane and potatoes; (iv) high protein content in cassava and oats; (v) greater fibre strength in cotton; (vi) higher oil content in oil palm; (vii) greater ecological adaptation in grapes; (viii) stronger roots in pineapple; (ix) short stature in wheat; (x) greater biomass, growth rates and delayed senescence which lead to higher yields, in major cereals; and (xi) cytoplasmic male sterility and restorer systems in many crops. Broadly, these additional genepools can be separated into two groups on priority:
|
Easy to exploit |
|
|
Wild progenitors |
: Closely related to crops and belonging to the primary
genepool. |
|
Other wild species |
: Relatively distantly related; cross-compatible; belong to
the secondary genepool. |
|
Difficult to exploit |
|
|
Wild species |
: Distantly related; unrelated taxa of different genera
(species); broadly falling in the tertiary genepool. |
Fig. 3. Altitudinal limits of forage plants in Western Himalayas
The difficulties encountered in collecting wild species/crop relatives may be enumerated as follows:
1. Variation in time of seed maturity in natural populations (even at the same survey site/location) in the distributional range of a species.The identification of species in the field requires the knowledge and aptitude for systematic botany coupled with that of ecology, geology, geography, pedology and anthropology. PGR collectors will have to acquire all this knowhow.2. Density of populations; number of fruits/seeds per plant vis-a-vis availability of sufficient material.
3. Flowering/fruiting/dormancy in horticultural material, particularly in fruit trees for collection of bud woods/vegetatively propagated material, etc.
Collecting is often very laborious and time-taking, and much patience is required to hunt for the desired wild materials; species growing in different ecological niches, littoral zone/mangrove types, on extreme mountain (top) ranges, desolate arid habitats; and the rare and/or endemic types. It is equally cumbersome to collect from top of tall trees (terminal crown branches bearing fruits in humid tropical forests); in situations when seed output is very low.
A high degree of perseverance is required in screening wild relatives for transferring the valuable traits to the agronomically suitable crops (Hawkes, 1977; Harlan, 1976, 1987). Maintenance and conservation of this material is imminent (Hoyt, 1988), through in-situ and ex-situ measures for effective utilisation (Ladizinsky, 1989; Chapman, 1989). Apart from traditional breeding, appropriate methods for gene transfer through biotechnological applications would open avenues for proper understanding and utilisation of secondary and tertiary genepools. The value of wild relatives is being better recognised now with more fruitful findings such as that of Zea diploperennis, a new teosinte from Mexico (Iltis et al., 1987); Oryza nivara from India, and several species of wild rice, in general, from Asia, and such other useful plants from different parts of the globe.
The details on the data to be taken at the collecting site are given in Appendix I (a and b) - samples of forms used by the NBPGR (adopted mainly from IBPGR) and that proposed by Hawkes (1983) for recording the passport data.
The amount of information which can be recorded during collecting activities is very much dependent upon, the time available. There is a minimum amount of information which must be recorded regardless of time. But other details may be regarded as being of only secondary importance by some, and to be kept to a minimum so that the time spent actually on collecting can be maximized. Others argue that extra time spent on recording additional information will save time later by avoiding some aspects of evaluation. Clearly, a compromise can and must be made in this respect.
Various designs of collecting forms, sheets or books have been used by collecting missions. The details given are more applicable to multicrop collecting. Specific crop missions will need different forms depending on the crop; the format for recording such information as adapted by IRRI for rice is given in Appendix II. Also, for wild species collecting, forage collecting, etc., specific format as per crop/plant(s) is to be designed.
The general strategy is summarised below (Hawkes, 1980). These points would further strengthen the knowhow of the collector alongwith the account presented above.
A. For seed collections (cultivated and wild species)
1. Collect from (30-) 50 (-100) individuals per site (50 seeds of each as one sample or less, if necessary, at random. One inflorescence per plant is generally suitable.B. i) For vegetatively propagated cultivated species2. Sample as many sites as possible according to availability of time.
3. Choose sampling sites over as broad an environmental range as possible. This should capture all alleles with frequency of 5 percent or more in the population.
4. Change tactics, where necessary, for wild species, that is, where individuals are scattered, you may need to consider that a population for sampling spreads over several square kilometres.
5. If considerable morphological variation is present in a population, make separate samples of each type.
6. Add biased sampling if some morphotypes are not included in random sampling.
7. Take whole inflorescences, as well as seeds, where necessary, as vouchers.
8. Make herbarium specimens, where possible.
9. Take photographs.
10. Write meticulous field notes.
1. Sample each distinct morphotype in a village.ii) For collecting wild vegetatively propagated species2. Repeat at intervals over an area.
3. Supplement with seed collections, where possible, and give same collection numbers if seeds come from the same plants as the vegetative samples. If they do not or are bulked samples, give separate collection numbers.
Collect just a single propagule from each of 10-15 individuals as a bulk sample (less if organs are very large, more if smaller, from area of about 100 x 100 m).
Depletion of genetic resources
Reassessment of collection priorities
Ecogeographical surveys
In-vitro germplasm collection techniques
In the priority areas/regions which hold rich native genetic diversity for different crops, the depletion of genetic resources is of E. different kind. This is visible in advanced or developed agricultural sectors where large impact of high yielding varieties operates as well as in other situations with ethnic diversity, agro-ecological variation and botanical richness. The causes of this depletion are as follows (Arora, 1988):
1. Rich natural vegetation, considerable crop plant diversity; as in the north-eastern region, Western Ghats and the Eastern Ghats. The loss of genetic resources has been:(i) through gradual impact of high yielding varieties, (ii) excessive biotic interference - large scale felling of trees/destruction of natural vegetation, shifting cultivation etc. There has been loss of native variability and endemic/rare cultivated and wild types and other economic plants.Apart from the above situations, depletion of genetic resources may also occur through impact of human preferences, newer usage of some plants - as of cluster bean (guar) for industry and change in land use pattern. Relative merit of each case is to be judged and pockets of diversity tapped accordingly for germplasm collection, realising the degree of threat to native variability. As for wild types, priority is to be given to areas falling in all the above categories subject to degree of biotic interference, over-exploitation of native flora, and in exceptional cases, to emergency situations like dam sites/submerged areas.2. Rich natural vegetation, enormous crop plant diversity as in the Western Himalayas. The loss of genetic resources has been largely due to: (i) spread of high yielding varieties, and (ii) over-exploitation of natural economic plant wealth, mainly medicinal plants. There is potential threat to wild endemic/rare useful plants.
3. Poor natural vegetation, relatively less native diversity; as in the northern plains/Indo-Gangetic plains. The loss of genetic resources mainly involves old bred cultivars due to the impact of high yielding varieties.
4. Large scale plantations/monocultures in categories 1 to 3 above: loss of endemic/rare/economic plants including the wild relatives and related species.
It is estimated that total germplasm accessions in different crops held by various crop-based institutes, coordinated projects, agricultural universities and including the NBPGR may number around 200,000. Further, much native diversity is also held by ICRISAT, Hyderabad (total holdings about 96,000 collections) in its mandate crops - sorghum, pearl millet, pigeonpea, chickpea and groundnut (and a sizeable collection of minor millets). Thus, in view of the exploration plans being coordinated by the NBPGR with crop-based institutes, agricultural universities and coordinated projects in priority areas and crops defined above, a reassessment of national needs in collection, and hence, reprioritisation is required. A critical evaluation of collections held is needed to assess the extent to which different geographical areas have been sampled and the extent to which diversity collected represents the available variation. For lack of feedback on source data and unevenness of evaluated data, such an exercise to a precision level may not be possible, but broad generalisation could be made in view of areas surveyed, reflecting the adequacy or inadequacy of collections held/made. This categorisation, priority-wise is (Arora, 1988):
|
Crop categories |
Remarks |
|
|
I. |
Collections inadequate/poor |
|
|
|
Horticultural crops, plantation crops, medicinal plant, wild
relatives |
Both regional and crop-specific emphasis needed |
|
|
Tuber crops, under-utilised crops, forages |
Both regional and crop specific emphasis needed |
|
II. |
Collections moderate/adequate |
|
|
|
Cereals, millets, vegetables, fibres, legumes and oilseeds
|
Only specific collection required with priority to grain
legumes and oilseeds |
The eco-geographical surveys are undertaken to determine the distribution of particular species in specific regions and ecosystems and pinpoint to patterns of infra-specific diversity, and establish relationship between survival and frequency of variants and associated ecological conditions (IBPGR, 1981). They are helpful in ascertaining the origin of crop plants, both geographically and biologically. Large untapped areas still exist on the globe and through critical assessment of regions of diversity (Zeven and Zhukovsky, 1975; Zeven and de Wet, 1982), additional information on many such areas/species is still required.
It could sometimes be possible to combine initial exploration of plant genetic resources with broader environmental assessments. Ecological and geographical data alongwith knowledge of species biology are necessary to determine minimum and optimum requirements for in-situ reserves. In particular, information related to determining needs for number of populations, area, sites, associated species and communities, and successional factors needs to be collected. Such data, in turn, are essential for evaluating the effectiveness of already established, protected natural areas for perpetuation of certain portions of targeted genepools.
The usefulness of such surveys depends on the scope and the environment to be studied, knowledge of the vegetation types which are associated with the target species. These surveys are further helpful in the identification of areas with particular types of agriculture and other landuse; understanding distribution of sites for collecting within the protected, natural areas. Further, more sophisticated studies involve gathering information in Landsat Multispectral Scanner (MSS) data which have been used extensively to examine and map vegetation cover. The role of the IBPGR which has been stressing on eco-geographic surveying must be appreciated (IBPGR, 1983).
In-vitro methods may in future be applicable to floral structures, immature embryos and vegetative tissues such as leaves, thus broadening the scope of the collector (IBPGR, 1984). The method has the advantage in the safe movement of germplasm. For example, in cassava, the materials are collected as stakes, taken to selected national programmes, meristem cultured and thereafter transferred to the world collection at CIAT. The work especially from remote locations could be greatly facilitated if in-vitro collecting techniques would be applied. There is a potential for excising zygotic embryos at the location of collection, for instance, in the case of coconuts and thus greatly facilitating the transport of collected material (for details, refer Chapter 11). Development of in-vitro methods for storage of zygotic embryos has been perfected.
By and large, germplasm collections have not been fully exploited in terms of their total potential. Emphasis has been laid towards yield contributing characters-agronomic/agro-botanical evaluation. The land-races must be assessed for their adaptability to stress-prone environment, reaction to diseases and pests and germplasm must be screened for quality characteristics. Use of descriptors and descriptor states as advocated by the IBPGR, incorporating the above parameters, would point towards effective utilisation of native variability. A critical assessment is required in terms of both observable and non-observable characters (Frankel and Soulé, 1981). In wild and primitive populations, reserves of cryptic variability are high, and hence their capacity for adaptive response. It is virtually impossible to know the full range of adaptive variability in a crop species and such genetic variation is as important as prevalent varietal diversity for genetic conservation. It is, therefore, important to maintain populations.
The strategies and methodologies of germplasm collection have been fairly well worked out (Hawkes, 1980), but must be followed with practical approach (Arora, 1981) in areas of operation, keeping in view the local environment. The sampling procedures, logistics and tactics in planning and undertaking PGR exploration programmes require much input from the collectors. The various components of this activity are summarized in Fig. 4 (Williams, 1978). The role of crop germplasm collectors is thus significant to the cause of capturing genetic diversity for its utilisation and conservation. Much rests on the competence of the collectors in taking on-site decisions as per needs of collecting targets. Certainly, there must be limits to the number of samples collected to capture genetic variability that can be handled effectively.
As already discussed, the breeding system of the population is important in determining sampling. Outbreeding species maintain variability in complex interactions among genetic and environmental factors. Even populations of inbreeding species contain individuals of many different genotypes and progenies frequently segregate for polymorphisms. From a genetic point of view, therefore, the seed accession collected in the field is usually a bulk sample of the population. By and large, the expertise of the collector has much to do with sampling, a factor so essential for such a work. Exploration targets/objectives must be well defined and made specific, to achieve maximum possible interaction with local counterparts. In the context of national needs relating to crop-specific collecting, even more emphasis may have to be given to resolve specific economic problems. Thus trait-specific collecting may be required, i.e., salt tolerance, cold tolerance, drought tolerance, early/late blooming, low chilling, specific root stocks in fruit trees, thin peel and oxalate-free types in taros/yams, tolerance/resistance to particular pests/diseases, adaptability to water logged habitats, tillering capacity, root system, branching, leafiness, etc., apart from quality characteristics. More meaningful evaluation would provide the desired feedback which is so necessary for future exploration endeavours. Further, such screening of accessions collected within India has pointed out to geo-graphical/agro-ecological pockets holding disease/pest resistant germplasm; in rice from north-eastern region, and from Kerala for pests such as the brown plant hopper, green plant hopper, white backed plant hopper, gall midge, stem borer; and diseases such as rice tungro virus, blast and bacterial leaf blight; to pea viral diseases in central and western Uttar Pradesh; and to soil salinity in durum wheats from northwestern Rajasthan and parts of Saurashtra (NBPGR reports/personal communication with Mr. T.A. Thomas, Principal Scientist, NBPGR; Presidential address of Dr. T.N. Khoshoo 'Environmental priorities in India and sustainable development', 1986, Indian Science Congress). It may also be ideal to reassess collections held in terms of core-collection or a condensed yet representative assembly of accessions by allocating accessions to related groups (Frankel and Brown, 1984), so as to reduce collections to manageable proportions. Rationalisation of collections is a necessary step for efficient management of genetic resources.
Fig. 4. The approach to germplasm collecting and sampling process (Williams, 1978)
A rather more specific study in terms of collection and utilisation of germplasm need to be made on wild relatives and related taxa, for which very poor collecting has been done, though areas of species diversity have been identified (Arora and Nayar, 1984). Such wild genepools, normally occurring in biotically disturbed habitats, are under threat and require immediate collecting to make use of their wider adaptability, tolerance/resistance to diseases/pests, yield/quality attributes and other biological characteristics. Basic bio-systematic studies on these in relation to their cultivated types will help meet future crop improvement needs; the understanding of evolutionary relationship between cultivated and wild species is undoubtedly of great relevance to breeders. It must be underlined that it is impossible to predict the breeding requirements of the future. This points to the need for conservation of genetic variability for use in both foreseeable and unforeseeable breeding work. In future, we may see breeding for genetic heterogeneity to reduce the risk of vulnerability and adoption of multiple cropping will clearly lead to shifts in selection criteria and agricultural practices. At present, biometrical genetics is giving us improved prediction for a genotype's performance in different environ- merits; in addition, better insight into the physiology and plasticity of the plants suggest that breeding programmes are likely to require broader genetic bases (Williams, 1978). It is as well to remember that the evolution of crop plants has not only resulted under the influence of man but also from orthogenetic evolution with shifts in morphogenetic and integrating mechanisms in the plants' physiologies.
The development of efficient exploration programmes for a particular species depends, according to Marshall and Brown (1975), on two levels of objective decisions: (i) where significant genepools of the species occur and where they are most threatened by extinction; and (ii) the areas covered by previous exploration missions and their relative effectiveness as measured by the material held in existing collections. The state of genetic erosion of a crop, and the status of world collections of crops must determine priorities for collecting, taking the national priorities also into consideration. IBPGR has drawn up lists of crops which are under grave threat of genetic erosion on a world basis. It may be pointed out that national programmes have also to keep in view the global collections held in different international centres under the CGIAR system and the regional collections held in various genetic resources centres in different countries. The role of active exchange links, thus, will also provide a feedback on national collections held outside the country e.g. of rice at IRRI, Philippines; of grain legumes, forages and millets with USDA, Fort Collins, USA; and on collections required from other geographical regions/gene centres. Some of these aspects, alongwith achievements made by the national programme at NBPGR on exploration and germplasm collection, are reflected in Chapter 14 of this book. Collecting is limited by the constraints, such as time available, physical capacity and competence of the collectors apart from other local factors. For a mission to be successful, a balance has to be struck between sampling according to theoretical strategies, cost-effectiveness vis-a-vis practical considerations. For instance, in relation to sampling units, the size of a population of primitive cultivars varies from a few square metres to hectares. In many cases, wild species show sparse distribution and may disperse their seeds. Thus, the number of plants that can be sampled may be small. In practice, these difficulties are to be judged and maximum possible variation captured, keeping in view the ecological and genetical background. Overcoming these practical realities is the major task of a plant explorer/collector. Further, considering the overall priorities and the paucity of expertise in this discipline, there is need for regular training programmes, both in national and international context.
Germplasm collection is one of the primary activity of plant genetic resources centres. It aims at capturing plant genetic diversity and, in this context, is an initial step to back up all the related PGR activities. The growth and development of this discipline and the activities taken up in India are highlighted since their initiation. Emphasis is mainly laid on the techniques of plant exploration and germplasm collection both for plant/crop specific and multiple-crop/economic-plants collecting. The theoretical knowhow and its implications against ethnic and cultural background of farmers who grow landraces is discussed and suggestions given to make collecting of germplasm more practicable. It is advocated that the discipline, being field-based, involves considerable knowledge of plant geography, agro-ecology, plant taxonomy/herbarium studies, ethnobotany, crop evolution and domestication, population variation and distribution, genepool sampling and several other related topics. More important of all, against the above details, the logistics and tactics involving exploration planning are elaborately dealt with. National priorities in crop-germplasm collection have been indicated, with equal emphasis on survey of areas rich in diversity of wild relatives of crop plants. It is clear that the only safe approach to providing broad genetic bases, and satisfying the needs of future plant breeding programmes is to collect and maintain as much as possible of the entire genetic diversity of both cultivated species and their wild relatives.
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Williams, J.T. 1978. Plant exploration: capturing genetic variability, pp. 14-24. In Conservation of plant genetic resources. Proc. British Assoc. for Advancement of Science, Univ. of Aston, Birmingham, U.K.
Zeven, A.C. and J.M.J. de Wet. 1982. Dictionary of cultivated plants and their regions of diversity. Wageningen. 259 p.
Zeven, A.C. and P.M. Zhukovsky. 1975. Dictionary of cultivated plants and their centres of diversity. Wageningen. 219 p.
NATIONAL BUREAU OF PLANT GENETIC RESOURCES, NEW DELHI 110 012
PASSPORT DATA SHEET
Date..................... Collector's
No.......................... Accession No......................
Species Name.......................................... Common
Name.................................
Cultivar/Vernacular
Name.................................Regions
explored.....................
Village/Block.......................
District...........................
State..............................
Latitude...............................N/S
Longitude..................E/W Altitude...............m
|
SOURCE |
: 1. Natural wild 2. Disturbed wild 3. Farmer's field 4.
Threshing yard 5. Fallow 6. Farm store 7. Market 8. Garden 9. Institute
10.......... |
|
STATUS |
: 1. Wild 2. Weeds. Landrace 4. Primitive cultivar 5.
Breeder's line |
|
FREQUENCY |
: 1. Abundant 2. Frequent 3. Occasional 4. Rare |
|
MATERIAL |
: 1. Seeds 2. Fruits 3. Inflorescences 4. Roots 5. Tubers 6.
Rhizomes 7. Suckers 8. Live plants 9. Herbarium 10................ |
|
SAMPLE TYPE |
: 1. Population 2. Pure line 3. Individual plant |
|
SAMPLE METHOD |
: 1. Bulk 2. Random 3. Selective (non random)
4................ |
|
HABITAT |
: 1. Cultivated 2. Disturbed 3. Partly disturbed
4................ |
|
DISEASE SYMPTOMS |
: 1. Susceptible 2. Mildly susceptible 3. Tolerant 4.
Resistant 5. Immune |
|
INSECT/PEST/NEMATODE |
|
|
INFECTION |
: 1. Mild 2. Moderate 3. High |
|
CULTURAL PRACTICES |
: 1. Irrigated 2. Rainfed 3. Arid 4. Wet 5................
|
|
SEASON |
: 1. Kharif 2. Rabi 3. Spring-Summer, Approx. Sowing
Date/Month............... Approx. Harvesting Date/Month...............
|
|
ASSOCIATED CROP |
1. Sole 2. Mixed with............... |
|
SOIL COLOUR |
1. Black 2. Yellow 3. Red 4. Brown 5................
|
|
SOIL TEXTURE |
1. Sandy 2. Sandy loam 3. Loam 4. Silt loam 5. Clay 6. Silt
|
|
STONINESS |
1. Stony 2. Pulverized 3................... |
|
LAND ASPECT |
1. Level 2. Crest 3. Escarpment 4. Rounded summit 5. Upper
summit 6................ |
|
SLOPE |
1. Terrace 2. Lower slope 3. Open depression 4. Closed
depression |
|
TOPOGRAPHY |
: 1. Swamp 2. Flood plain 3. Level 4. Undulating 5. Hilly
dissected 6. Steeply dissected 7. Mountainous 8. Valley |
|
AGRONOMIC SCORE |
: 1. Very poor 2. Poor 3. Average 4. Good 5. Very good
|
|
Collector No. |
Collector No. |
Collector No. |
Collector No. |
|
Expedition
Organisation:...................................................................................................................... |
|||||
|
Country:................................................................................................................................................ |
|||||
|
Team
Collector(s):............................................ |
Collector's
Number:............................................... |
||||
|
Date of
Collection:............................................ |
Photo
Number(s):.................................................. |
||||
|
Species
Name:..................................................................................................................................... |
|||||
|
Vernacular/Cultivar
Name:.................................................................................................................... |
|||||
|
Locality:................................................................................................................................................ |
|||||
|
............................................................................................................................................................. |
|||||
|
............................................................................................................................................................. |
|||||
|
Latitude:........................... |
Longitude:................................... |
Altitude:...................................... |
|||
|
Material: |
Seeds |
Inflorescences |
Roots/tubers |
Live Plants |
Herbarium |
|
Sample: |
Population |
Pure line |
Individual |
Random |
Non-Random |
|
Status: |
Cultivated |
Weed |
Wild |
|
|
|
Source: |
Field |
Farm Store |
Market |
Shop Garden |
Wild |
|
|
|
|
|
|
vegetation |
|
Original Source of
sample:.................................................................................................................. |
|||||
|
............................................................................................................................................................. |
|||||
|
Frequency: |
Abundant |
Frequent |
Occassional |
Rare |
|
|
Habitat:................................................................................................................................................ |
|||||
|
............................................................................................................................................................. |
|||||
|
Descriptive
Notes:................................................................................................................................ |
|||||
|
............................................................................................................................................................. |
|||||
|
............................................................................................................................................................. |
|||||
|
............................................................................................................................................................. |
|||||
|
Uses:.................................................................................................................................................... |
|||||
|
............................................................................................................................................................. |
|||||
|
Cultural Practices |
Irrigated |
|
Dry |
|
|
|
Season: |
Approximate sowing
dates:................................................................. |
||||
|
|
Approximate harvesting
dates:............................................................ |
||||
|
Soil Observations: |
Texture:............................................................................................... |
||||
|
|
Stoniness:............................................................................................ |
||||
|
|
Depth:.................................................................................................. |
||||
|
|
Drainage:............................................................................................. |
||||
|
|
Colour:................................................................................................. |
||||
|
Soil
pH:................................................................................................................................................. |
|||||
|
Land Form: |
Aspect:................................................................................................. |
||||
|
|
Slope:................................................................................................... |
||||
|
Topography: |
Swamp |
Flood Plain |
Level |
Undulating |
|
|
Plant
Community:................................................................................................................................. |
|||||
|
............................................................................................................................................................. |
|||||
|
Other crops grown near in
rotation:...................................................................................................... |
|||||
|
............................................................................................................................................................. |
|||||
|
Pests/Pathogens:................................................................................................................................. |
|||||
|
Name and Address of
farmer:.............................................................................................................. |
|||||
|
............................................................................................................................................................. |
|||||
|
Taxonomic
Identification:..................................................................................................................... |
|||||
|
by...................................................................... |
Date:..................................................................... |
||||
|
Name of
Institution:.................................................................... |
Accession No:............................. |
||||
