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Germplasm collection
Ramni Jamnadass
Ian Dawson
Tree Domestication Course
Nairobi
17 to 22 November 2003
Overview
• Reasons for collection?• Rangewide or local collection?• Collection approaches?• Practical issues?• Examples
Reasons for collection
• Immediate need expressed by farmersusers- national (farmers, extension workers, NGOs, researchers) or international (researchers) levels
• Conservation purposeswhere in collections, diversity represented is missing/ or insufficient ex situ storage, circa situ (on farms) and in situ
The natural resource base of many current or potentially useful species is being eroded
• Management researchDetermine seed physiology characteristics (increase longevity; decrease dormancy; increase germination rates, monitor germplasm health..)
Reasons for collection (2)
• Genetic improvement programmes
Collection to evaluate potential genetic improvement
Conventional breeding
Biotechnological enhancement of germplasm (pathogen resistant; drought resistant, enhanced product..)
The provision of superior tree germplasm can increase the uptake of, and return to farmers from, agroforestry systems
• First step in programs aimed at exploitation or conservation of plant genetic resources for future evaluation and utilization is the collection of those resources.
• A plant collector is a researcher consciously seeking to understand and record the bases of the adaptation of the plants to their general and specific environment and agricultural systems.
• He can do his job best against an in-depth background of knowledge of the ecological, human and agricultural characteristics of the area
Collection for domestication
• Diversity within ecological niches
• Diversity within and among species of important character traits (build up through evolutionary processes that keep provenances apart and impose adaptive pressures)
• Diversity of functionality (uses)
Rangewide or local collection?
Rangewide sampling (aims to capture genetic diversity built up through evolutionary processes that keep provenances apart across the ecogeographical range of a species)
Involves collecting numerous provenances across both geographical space and ecological clines (such as rainfall, soil and altitude gradients).
Rangewide or local collection? (2)
• Scale of collection (rangewide or local) depends on:
• Practical issues of germplasm exchange (e.g. recalcitrance)
• Legal issues of germplasm exchange• Relative focus on genetic improvement versus
physiological management• Importance of local genetic resource management• Trend toward community involvement
Collection approaches
• Strategies for sampling• Random systematic• Targeted• Seed• Vegetative
• Trend for community involvement• Advantages and disadvantages
bactris
Practical issues
• Rationale• Exploration• Logistics• Documentation• Biological standards• Flexibility• Processing and storage
prunus
Exploration
• Right time for seed collection • When the fruits/seeds are mature ?• How should tree seeds be collected ? • How do I know how much to collect? • Is it better to collect from the natural
forest or purchase seeds from a farmer?
• How do I handle fruits between collection and processing?
Basic Collection Strategy (Flexible)
When information on the population structure of the target species is lacking:
• Collect from 30-50(100) healthy mother trees• If insufficient material for procurement, sample more
sites• Sampling within a site should be random wrt phenotype,
but representative wrt to ecological variation• Sample as many sites as possible within the time
available• Ensure that sample sites represent as broad a range of
environments as possible• In natural forest, ensure regular distribution of seed
trees by keeping a distance of 50-100m
Examples
• Calycophyllum spruceanum• Prunus africana• Sclerocarya birrea• Warburgia ugandensis
calycophyllum
Examples (2)
• Dacroydes edulis
• Irvingia gabonensis and
I. wombolu• Case study Irvingia boy