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Strategies for Collecting Bamboo Germplasm - V. Ramanatha Rao

Senior Scientist (Genetic Diversity/Conservation), International Plant Genetic Resources Institute (IPGRI), Regional Office for Asia, the Pacific and Oceania (APO), P.O. Box 236, UPM Post Office, 43400 Serdang, Selangor Darul Ehsan, Malaysia.

Introduction

It is widely recognized that the plant genetic resources (PGR) are the basis for sustained plant improvement. PGR of any genepool constitute all the plant materials that are out in the field or in the wild and in various collections that are maintained outside the natural habitat. In many cases we know very little about the PGR of most genepools and much more is to be understood about them for proper conservation and use. In this connection, collecting and conservation of plant germplasm assume special significance. Collecting and evaluation are part of long term strategy for plant improvement that is designed to broaden the genetic base of a plant species with respect to genes controlling quantitative characters and other desirable traits (Lawrence 1995). Collecting plant germplasm can include various aspects such as survey, exploration, rescue missions, bioprospecting, network activities etc. Due to changes in the international scene in the recent years, for example Agenda 21, the Convention on Biological Diversity (CBD) and Global Plan of Action (GPA), it is expected that exploration for monitoring and PGR collecting will increase. General principles of collecting plant diversity are well reviewed (Guarino et al. 1995). However, bamboo collecting has always been in the context of taxonomic studies; hardly ever from the point of view of collecting and conserving genetic diversity. In view of this, the Third INBAR/IPGRI Biodiversity Genetic Resources and Conservation Working Group Meeting (Ramanatha Rao and Rao 1998) strongly recommended that a bamboo germplasm collecting/sampling strategy be developed. So it is an opportune time to look closely at this issue. This training/workshop is also an appropriate forum to assess critically this draft strategy so that it can be improved. The strategy developed for fruit tree species has been extensively used in developing this document (Ramanatha Rao 1998).

Determining the most optimum sampling strategy for any species and/or region is important. At the same time it is often a difficult task. It is important because this determines the representativeness of the samples collected in terms of the genetic diversity. The quality and quantity of the plant genetic resources that will survive for the future also depends on this decision. Defining the sampling strategy can often be difficult because it is influenced by the complexities of the range of species, genetic structure of plant populations and the uses to which the samples may be put.

It is essential to remember that we are dealing with bamboos, a highly variable species group. Defining the most appropriate strategy for such a variable group is indeed a difficult task. The difficulty arises mainly, among others, due to the fact that we have very little information on genetic structure of the populations, which can often be very complex (Allard 1970). The taxonomy is in flux and at present we are focusing only on a few priority species. We also have insufficient information (almost non-existent) on the types, amounts and distribution of genetic diversity within and between bamboo populations. In addition, we are also not able to pinpoint the threat of genetic erosion facing many bamboo species, populations and habitats, a factor that determines the urgency for collecting and recording of data in simple usable form.

Bamboos also have some of the singularities of forest trees, that bear on any collecting strategy that is advocated. They are characterized by longevity and can produce abundant number of progenies that are subjected to severe selection pressure. Some of the bamboo species, like a number of forest trees, are very widely distributed, giving rise to problems of delimitation. We also know that these are subjected to, over a long term, to highly complex and variable environments and most of them thrive well under different ecological conditions. They also present longer life cycle than most biotic pests that attack them, thus changing the host-pathogen relationships. The unique and often unpredictable flowering and seeding behaviour of many bamboo species make any systematic seed collecting and breeding programme almost impossible. This mass seeding phenomenon reduces seed collecting option. All these factors further make the development of collecting and conservation strategy much more complex compared to one that is needed for short-lived annuals or trees that flower and reproduce regularly.

The overall objective of most collecting programmes is to conserve the genetic adaptability of species/populations (Hattemer 1994; Geburek 1997). More specifically, this is to identify and collect maximum genetic diversity, to properly document, and to undertake follow-up research on germplasm collections and to make the results and information available to the scientific and user communities. However, in perennial species like bamboos, can we afford to collect at random, the maximum genetic diversity? An attempt will be made here to try and find answers to this as well as many other questions. I wish to point out at the outset that what follows is a generalised model that gives the components of a strategy to build up the actual strategy. From discussions that follow, it may be possible to develop a comprehensive strategy for the collecting of bamboo genetic resources.

The strategy

It is important to clearly define the objective(s) of a PGR collecting mission. There can be several reasons for collecting, for example, 1. danger of genetic erosion, 2. clear need for use in improvement, 3. missing in the extant collections, 4. Taxonomic clarification, verification or confirmation and 5. needed for biological studies (Guarino et al. 1995). It is also essential to remember that collecting is not the end but the start of a series of follow up activities.

Defining objectives clearly at the outset will greatly help in developing a strategy (or strategies) for collecting since any strategy that will be followed is dependent on it. The objective of a collecting strategy is to develop a pattern of collecting which will include maximum genetic diversity occurring between and within populations in different or within the same geographic areas (Ramanatha Rao 1998). At the same time in plant species like bamboo, it is important to be able to collect the most useful material and 'elite' germplasm. This is mainly because of the perenniality as well as the long gestation period needed for the plants to become useful and the long time before any improvement programme in bamboo and similar species could be undertaken using the germplasm collected. The emphasis in the past has been on “plus” types rather than known and measurable superior genotypes. So, some selective sampling at the time of collecting, in place of or in addition to random collecting for genetic diversity will be useful. Since total number of samples that can be collected and handled effectively can be a limiting factor, the strategy would be “to capture the maximum amount of useful genetic diversity with a minimum number of samples” (Marshall and Brown 1983). Both scientific and practical knowledge will be most useful in carrying out this exercise.

A benchmark criterion

Before we proceed further it may be appropriate to look at what could be a guide line for sampling, as sampling considerations cut across all activities that we will consider in germplasm collecting. The original sample, quality and quantity, govern almost every decision we make on the germplasm at later stages.

We are all aware that our main interest is in genetically controlled traits. We are also aware that alleles are forms of a gene which are alternative in inheritance because they are situated at the same locus. When we talk of genetic diversity we are mainly referring to the diversity of alleles in a sample or population. While sampling, the probability of capturing alleles with certain frequency increases with greater sample size collected initially. However, this increase will be very little after a certain sample size has been reached. Given the diminishing rewards for effort expended on any one population is there a reasonable objective to guide the collector as to when a sufficient sample is adequately collected? (Brown and Marshall 1995). The objective should be to include in the sample at least one copy of 95% of the alleles that are present in target population at a frequency greater than 5%. While the biological basis for this criterion is debatable, the point is that increasing the certainty level higher than 95% or dropping the critical allele frequency below 5% would increase the sample size with only marginal gain. Brown and Marshall (1995) state that a sample of 59 random unrelated gametes from the population is sufficient to attain this objective. (The critical point to note here is the unrelatedness). This would be assured by collecting and bulking seeds or vegetative material from 30 randomly chosen individuals in fully out breeding sexual species, or from 30 random genotypes in an apomictic species or from 59 random individuals in a self-pollinating species. Thus a sample of 50 individuals can be considered as a benchmark for most germplasm collecting purposes. We will revisit this issue when we consider target diversity.

Collecting missions

Because of resource constraints, many collecting missions have a very long and varied list of target species (Engels et al. 1995). Typically all useful plant species in an area or a group of species will be sampled. This is in contrast to other missions, for example, those organised by plant breeders. The latter will have a sharp focus on particular gene pools, species or even genotypes. Thus it is possible to have different types of collecting missions. For bamboos, like many other crop/domesticated species, exploration, survey and collecting missions can take the following forms:

Conservation-oriented missions

The conservation of genetic diversity in a given genepool per se is the overall objective of conservation-oriented missions. For this purpose, random sampling should be employed. We should aim at sampling a class of alleles termed “locally distributed (in one or a few adjacent populations)/common alleles (alleles with a frequency greater than 0.05) by sampling 50-100 plants per site. The sites should represent environmental heterogeneity as much as possible (as defined in Marshall and Brown 1975). It is important to note that sampling 50 to 100 bamboo plants/clumps may be very difficult. In such a situation one should consider reducing the number of plants and increase number of sites or populations sampled thus including as many alleles as possible.

Targeted collecting

In this type of collecting, plants/populations are targeted for particular traits, or it involves collecting in specific agroecological areas/sites known to or thought of possessing some desirable traits including unique variants. This is a typical collecting strategy of breeders/crop improvement people. This type of collecting presupposes that bamboo germplasm was collected from these areas earlier and that they have been evaluated/screened thoroughly for the traits under consideration, but this may not be the case in reality. In many collecting strategies, the needs of the users of germplasm play a significant role. Also, this probably differentiates most the germplasm collecting from a botanical collecting. There is a need to prioritize any collecting of agricultural biodiversity and to do so we will need to consider the needs of the genebank curators, researchers and people involved in improvement. In such situations selective or targeted sampling strategy should be adopted. In this case, biased sampling of particular bamboo populations or clumps in pre-determined sites may have to be carried out. Knowledge about the species that are being collected is of paramount importance. However, as we all know that there is hardly any comprehensive evaluation on bamboos as yet, this type of collecting may be appropriate in future. For the time being, collecting for a specific bamboo species can be considered as targeted collecting.

Collecting due to genetic erosion

This is also referred to as emergency collecting. This is typical of “rescue missions” in areas or populations characterized by high genetic erosion risk or even threatened with extinction due to impending developmental activities or other disturbances. This type could be a collecting mission for conservation or a target collecting in habitats/populations that are known to be threatened due to genetic erosion. To do a good job, we will need information on types and rates of progress of genetic erosion. An example for this type of collecting could be one that is undertaken in an area that is expected to be submerged due to the construction of a dam or areas that are being threatened due to forest fires, particular land use changes etc.

In addition, collecting missions can also be classified as multi-species or species specific collecting, wild species or cultivated species collecting, single visit or multiple visit collecting and institutional (formal sector) or community (informal sector) collecting.

Multispecies or single species collecting

In a multispecies collecting mission, a region is targeted and an attempt is made to sample as much as possible of the diversity of as many species as possible. Conservation more than immediate use is the reason for this type of collecting, an extreme example being emergency collecting. A major draw back is that the collectors may not have in depth knowledge of many of the species that would be targeted to be collected. This can result in inability to follow optimal sampling procedures and thus the samples collected would be less than ideal. Furthermore, it will be impossible to collect a number of species with different flowering and maturation times even if the species are sympatric in distribution. This may not be a problem while collecting vegetative material of bamboo species, nevertheless, it will reduce the option of collecting sexual propagules, seeds or wildlings. In contrast, species-specific missions tend to be driven by the eventual users and the team members would be knowledgeable about the species being collected (Engels et al. 1995).

While carrying out a multispecies collecting, it is important to determine the sites with high species diversity. Diversity can relate to either diversity of species within a habitat or the diversity of habitats within a landscape (Usher 1992). For species diversity, with which we are concerned here, the simplest measure is a count of the number of species present in an area - species richness. However, to be of really useful, this needs to be weighted with the number of trees/clumps or populations of a particular species. So in such a situation one may have to compute Shannon index (which is based on Simpson index) which indicates species diversity in a site. Habitat diversity is more complex as one needs to define a habitat first and it can relate to either botanical composition or to geographical or to soils etc. Once defined then habitat diversity index can be determined. Usually one can determine the bamboo species diversity through an initial exploration and then it is advantageous to plan collecting in diversity rich sites.

Single-visit or multiple-visit missions

Most collecting missions tend to consist of a single, fairly short visit to the target area. Generally limited resources are the reason for such a strategy. As opposed to multiple-visit missions, single visit missions will not be able to take into account the considerable variation that can be there within a region in the timing of fruiting, accessibility etc., and a single visit may be very difficult to optimally time proper collecting of samples. Year-to-year variation can also be overlooked by single visits. Sometimes it may not be possible to correctly identify some of the species with a single visit. Thus, resources permitting, multiple-visit missions are recommended, at least an exploratory visit followed by a collecting mission. The preliminary survey visit can help in the proper identification of species in the target areas, collecting in situ evaluation data as well as material for genetic diversity analysis, results of which could be used effectively for collecting during the next visit. The exploration stage can also be used to acquire socioeconomic, ethnographic, ethnobotanical data, in particular indigenous knowledge. Repeat visits also help in monitoring genetic erosion. When multiple visits are not possible due to inaccessibility or resources constraints, then one may want to consider the option of training local people in collecting (Mr L. Guarino, 1998, personal communication).

Output of Germplasm collecting

Along with the objectives, we need to identify clearly the expected outputs from the collecting mission - genetic diversity sampled; existing ecological conditions, samples collected, herbarium specimens collected etc. Some of the outputs may arise (as a matter fact) from the actions taken, but it is important to note them so that modifications to the strategy can be carried out as necessary.

The major output is a set of samples that are representative of a range of maximum genetic diversity in the target genepool/species/populations. Along with such samples, information on the samples and their habitat is also collected. Since almost every collecting mission subsumes survey and monitoring aspects, another output could be techniques/methodologies used to identify species, areas, sites and levels or targets of diversity for collecting and recommendations as to areas for in situ conservation. Agroecological information, indicators to erosion, diversity analyses (that are done either at the pre-collecting stage or carried out during the mission itself), and indigenous knowledge (IK) etc., can help us to identify areas/sites which could become part of a protected area system or part of community conservation programme.

Human resource development in the form of skilled and well-trained explorers and collectors of plant genetic diversity is an offshoot of any collecting mission. As we all know, lack of sufficient skilled personnel in PGR artivities, including germplasm collecting, is a major problem for efficient collecting and conservation of bamboo germplasm, and collecting activities help to develop practical skills in this area.

The target diversity

For enhancing the efficiency of collecting missions collectors need to distinguish between various types and structural levels of variation. Some examples are:

· Heritable vs. non-heritable variation.

· Cryptic vs. expressed variability: What collectors see by the eye is “phenotypic variation”.

· Morphoagronomic and morphological vs. physiological and biochemical variability

· Variation between and within populations

· Ecotypes and agroecotypes vs. geographic races

· Polymorphism (allelic series for a variety of traits) and polymorphic loci

· Simple genetic variation (alleles, heterozygotes but no allelic series), simple loci

· Selectively neutral vs. adaptive allelic variation

· Genotypes vs. alleles (objective of conservation: single alleles, gene complexes or super genes, genotypes)

· Allele frequency and distribution, “wide-spread” - occurring in many populations in the area, “local” - occurring in one or a few adjacent populations in the target area.

Some discussion on sampling within and between population is needed. The pattern of genetic variation of a given trait within a population is best described by its frequency distribution, the most common being normal distribution (Snaydon 1992); it may be skewed if there has been directional selection. When a population with normal distribution is sampled randomly, the chances of capturing the genetically extreme individuals (rare alleles) will be rare, but it will be easy to calculate the sample size. The probability of this can be increased by increasing the size, up to a point. However, once the threshold size is past, the law of diminishing returns operates and the probability of capturing the rarer alleles will become less and less. Determination of optimum strategies for sampling populations within species is more difficult than sampling within a population. This is mainly because of the fact that we know much less about the variation between populations than we know about the variation within a population. If the main objective of the collection is to sample the variation present then for both within and between populations, random sampling appears to be the only method. However, if the collecting is for providing diversity for a breeding programme, then sampling of extremes (populations) probably is more useful. To do this successfully we need to have information on the variation within different populations.

This we can extend to alleles. Marshall and Brown (1975), Brown (1978) and Brown and Marshall (1995) elaborated on allele frequency and proposed four different classes: i. Common and widespread alleles (frequency >5% found in >10% of the populations), ii. Common and local alleles (frequency >5% and found in <10% of the populations), iii. Rare and widespread alleles (frequency 5% and found in >10% of the populations) and iv. Rare and local alleles (frequency <5% and found <10% of the populations). The common-widespread and the rare-widespread alleles are independent of the sampling strategy while sampling of rare-local alleles is impractical. The focus is on the locally-common alleles. The objective of random sampling strategies (Marshall and Brown 1975) “is to capture at least one copy of 95% of the “locally common” alleles occurring at frequencies higher than 0.05”. This will be assured if a sample of 59 random unrelated gametes from the population is made. In sexually reproduced outbreeding species (e.g. most of the fruit tree species) this would mean a reference sample size (bench mark criterion) of 30 randomly chosen individuals from a heterogeneous outcrossing population or a 59 random individuals in a selfing species. The priority will be to capture “common local alleles”.

In the case of bamboo, we know virtually nothing of the genetic variation (Williams 1995). Though some information is available on interspecific variation in bamboos (Rao and Ramanatha Rao 1995), much information is lacking hence cannot guide a collector. Specifically we know very little about the quantitative variation. So while making collections, some sort of generalizations based on the observation noted on earlier collections will have to be made. For example, allele distribution, hardly any information on genes and alleles is available in the case under consideration. However, based on experience one can determine the relative abundance or rarity for a particular trait and check for the same in a population that is being sampled. In this way, it should be possible to make certain generalizations and use them in developing the collecting strategy.

Many times, due to limitations of time and funds, only a very few populations have to be selected from a known set of bamboo populations. In such cases, it may be important that maximum genetic diversity has to be collected in very few samples. Theoretically it is possible that less than 100 clumps will have to be sampled at random from each population as to capture alleles with frequencies <1%, with very high probability (Lawrence et al. 1995). This needs to be tested.

Essential prerequisites of a collecting strategy

While developing an appropriate collecting strategy for any given genepool and to plan collecting missions efficiently, a certain amount of biological and agroecological information needs to be gathered and analysed. Without such knowledge any strategy will fail. Here it is not possible to deal with all the information needed, much of it can be found in Guarino et al. (1995). Some examples of such pre-requisites are given below:

Taxonomic information

As one can see this is fundamental to any collecting. Phylogenetic information that can provide species relationships, however basic it might be, can help greatly in collecting germplasm on a genepool basis. There is a great amount of confusion and uncertainty in bamboo taxonomy, but useful groupings of species can be made on the extant classification. There may be a need for different strategies for different species due to dissimilarities in reproductive biology, phenology etc. Hence correct taxonomic classification is the key to accessing other information needed about the target material.

There are several data sources for taxonomic information. Germplasm collectors need to be able to identify bamboos, to determine their accepted names and know something about where they grow (Prendergast 1995). It is essential to start with the key works on bamboos for each country for the target areas, such as the floras and monographs. There are several international, regional and national floras and the floristic works that can be consulted. To get more information on the ecology, one could consult world, continental, international and large ecological works. Now there are several international databases that are available for consultation. To familiarize oneself with the plant material, one needs to consult the herbarium materials. In addition to national herbaria, herbaria at Washington, Kew, Leiden, Paris and Australia, would provide valuable information to the collectors, where most of the international collections and type specimens are deposited.

Reproductive biology

Information is needed on the nature of the breeding system of the target species. Information on the levels of outcrossing in the crop species, the amount of geneflow between populations or species, inter and intraspecific classification of identifiable genotypes, geographical distribution and ecological amplitude etc. We do not know much about the reproductive biology and mating systems in bamboo. The extraordinary and apparently unpredictable flowering behaviour of the majority of species of bamboo makes it impossible to design systematic collecting or breeding programmes (Lawrence 1995). Some are known to flower regularly but are usually sterile as the glumes do not contain any seeds. The bamboo species that flower and produce seeds appear to be cross-pollinating which are morphologically highly variable. It can be assumed, therefore, that natural bamboo stands consist of a large number of different genotypes and that for those species with wide geographic distribution, different populations contain different arrays of genotypes (Lawrence 1995), presenting a sampling problem. Even though, given this complex mating system, making generalizations based on the available data is difficult, most bamboo species may be treated as cross-pollinating and sampling based on this can be determined. In addition, although flowering of the majority of bamboo species is unpredictable, it might be possible to collect sexual progeny (of those species that flower and produce fertile seeds) from flowering stands either directly, as open pollinated seed (a population sample), or indirectly, as seedlings that arise around the flowering clumps. It may be wise, if immediate evaluation of the material is planned, to keep material from different clumps as distinct samples (Lawrence 1995). Clumps should be chosen at random as should be the seed or seedlings collected from them.

Information on past collecting

A given area might have been explored or even sampled in the past. Any information such as description of regions and sites sampled, observations on the variation in the field/habitat, recommendations for further collecting, observations on rate and causes of genetic erosion, characterization and evaluation data, distribution of genetic variation within and between populations form results of analyses of collections, the useful genetic diversity identified and used in crop development programmes etc., can guide the development of a strategy. Bamboos have been collected in the past mainly for taxonomic purposes. Information on such collecting can provide us with details on distribution which can be used for developing the strategy.

Site information

Ecogeographic information such as vegetation and soil maps, herbaria records (label data) etc., can provide a full picture on species distribution range and on its environmental heterogeneity. For bamboo, developing distribution maps superimposed over ecogeographic information is in its initial stages and needs to be further strengthened. This kind of information is essential because the relative adaptability of the species or their varieties to a given set of edaphic and environmental conditions need to be well determined if they were to be conserved or used in reforestation programmes and plantations (Rao and Ramanatha Rao 1995).

Landuse information

In recent years, the changes in landuse pattern have been dramatic. Hence, collectors need to access the latest land use information which can provide clues to genetic erosion and potentials for in situ conservation (L. Guarino, 1998, personal communication). Accessing this type of information can help the collector to prioritise the sites for collecting.

Indigenous knowledge

Information about cultivation and agronomic practices, farmers preferences and selection, use of crop cultivars etc., is the basic information on the incipient genetic diversity of the material targeted. We all are aware that bamboo had been used by indigenous people for thousands of years. During this period, vast amount of traditional knowledge about bamboo, its ecology, distribution, classification and uses must have accumulated. Such details need to be gathered, analysed and relevant points to be used in developing a collecting strategy.

Decision-making process of sampling strategy

While developing a collecting strategy for a bamboo genepool, a number of decisions need to be made about many issues based mainly on the pre-requisite information. So the accuracy of the information on hand will determine the efficacy of any strategy developed. Some of the decisions that need to be made are discussed below.

As representation of genetic diversity is the major concern in most of the missions, collecting genetic resources should be based on population and not on single plant/clump. However, in the case of bamboo species, considerations such as the gestation period of germplasm, resources required to maintain a true population sample will have to be looked into.

Sampling method needs to be determined, i.e. should it be random or non-random (selective) sampling. The objective in conservation of PGR is to maintain 'a representative sample' of the genetic variation contained within and between populations. This objective can only be met through random sampling. However, some level of selective sampling will be required considering the value of germplasm to be collected, especially when one is looking for elite bamboo materials for immediate use. In the case where the population is sampled at random, environmentally induced phenotypic variation will not affect the outcome of sampling, while in the case of selective sampling may be affected by the variation induced by environment. However, if environmentally induced variation partially conceals genetic variation, as commonly happens in the field, selection of extreme types (selective sampling) will be less effective (Snaydon 1992).

Prior to the collecting mission, decisions about the components of sampling strategies have to be made. These include decisions regarding the number and distribution of sites per region, number of plants/clumps per site, number of seeds or other propagules per tree or plant/clump to sample have to be made based on the biological information as well as on practical feasibility.

There is a need to assess the implications of the choice of a method on various practical issues such as resources required, time etc. For example, if the decision is to collect samples from at least 50 plants/clumps per site from as many sites as possible (depending on the heterogeneity of the environment in the target area), then resources required to cover a given area in a certain amount of time have to be determined beforehand so that the samples collected are well established in the new site.

We also need to determine the size of sampling sites and select sampling sites. The sizes are determined in turn by the size of farmers' stands or in terms of a colony of species. The size of a colony may be determined by factors of environmental heterogeneity, by observed variation, etc. Selection of sampling sites depends on distribution pattern and density of individuals, occurrence of unique variants etc.

In inbreeders (and in apomicts), populations generally diverge widely for the alleles they contain and for the amount of genetic polymorphism. Hence there is need to sample a greater number of populations within each region. This may have to be accomplished at the expense of the number of plants per site. Increase in sample size collected in exceptionally highly polymorphic populations may be the optimum strategy. In natural selfing populations, local subpopulation structure can develop in response to microsite/environmental heterogeneity. In such situations “stratified local sampling” at the given site(s) will be appropriate (Brown and Marshall 1995).

Some modifications based on specific needs have to be made. Special considerations while collecting in the wild will be required, for example, sampling at evenly-dispersed sites within the target area. In the case of cultivated bamboos, when it is very difficult to determine the samples to collect based on phenotypic variation, clustered sampling of sites within the target area will be useful. As would be the case in collecting bamboo species, budwood vegetative material from 10-15 individuals per site in close clusters may prove to be appropriate.

Generally information on the distribution of genetic diversity of bamboos between and within populations is either limited or completely lacking. Also, intensive sampling is undertaken following an initial preliminary exploration/collecting in the first year and subsequently the search for specific genotypes or genes of particular traits, e.g., specific adaptation to certain ecological conditions, drought tolerance, disease resistance etc. In such situations use of coarse grid sampling will be useful to sample maximum useful diversity. This involves, random sampling at wide intervals in an area where the size of the intervals is determined by environmental heterogeneity factors e.g. climate, soil, water availability, vegetation, growers' practices, genotypes, altitude, latitude etc.

Conclusions

Some sort of step wise decision making process needs to be developed so that a collecting strategy for bamboo genepool can be developed. Based on the discussion presented so far, which is far from being exhaustive, the following steps are suggested. It should be noted that this is not a blue print for germplasm collecting, but only a conceptual base to develop a strategy.

· Clear and well-defined objective(s) needed for example, to capture the maximum amount of useful genetic diversity with a minimum number of samples or to capture useful genetic variation for improvement programme.

· Prioritize the materials to be targeted, based mainly on the needs for improvement and potential for use.

· Determine type of collecting mission based on the objective, however, given the current thought, a combination of conservation, use and genetic erosion concerns need to be addressed. Information on these aspects needs to be assembled to make appropriate decision.

· Chalk out the outputs of a collecting mission clearly to facilitate their achievement by the mission.

· Familiarise with various types and structural levels of variation that can be present in target population.

· Based on the taxonomic information and economic use, determine the target species (of a genepool under consideration) to be collected.

· Based on information on past collecting, conservation and evaluation activities in the region/on the genepool, further refine the target area/genepool.

· Based on the objective(s), site information, information on breeding systems and indigenous knowledge etc., determine sampling techniques that need to be used.

· Sampling strategy needs to be determined based on a number of issues (as described in the section above), which should be basically random sampling with appropriate use of selective and stratified sampling as required.

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