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Tree seed supply chains

Tree seed supply chains. Tree planting on farms in East Africa: how to ensure genetic diversity?. David Boshier, Ian Dawson & Ard Lengkeek. Location of the countries and survey areas. Location of nursery survey sites. Uganda. Kenya. Mabira. Meru. Kabale. Nairobi. Arusha. Tanzania.

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Tree seed supply chains

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  1. Tree seed supply chains Tree planting on farms in East Africa: how to ensure genetic diversity? David Boshier,Ian Dawson &Ard Lengkeek

  2. Location of the countries and survey areas Location of nursery survey sites Uganda Kenya Mabira Meru Kabale Nairobi Arusha Tanzania

  3. Nursery sites

  4. Why bother about genetic diversity? • adaptation to changing environments • direct use of genetic resources • viability of populations in short term • - seed production • - inbreeding depression

  5. Inbreeding depression in Acacia mangium in Sabah Seed source 1st generation 2nd generation 3rd generation Seedling height (cm) 32.5 20.7 18.1 Sim, 1984

  6. Theory • direct impacts • decrease population size • increase spatial isolation • decrease densities • change local environment genetic processes genetic drift gene flow mating - inbreeding selection

  7. Bottleneck  genetic drift

  8. Isolated trees – mating patterns?

  9. Altered mating patterns in farm trees? • Predictions: increased inbreeding • greater pollen dispersal • fewer sires • Isolated farm tree Continuous forest sires inbreeding dispersal

  10. How many trees to collect from?

  11. Data collected in a survey of seed-propagated tree species in tree nurseries from five areas in East Africa

  12. Cupressus lusitanica Wind pollinated Hermaphrodite, self compatible 100,000 seed produced per tree

  13. Calliandra calothyrsus Bat/moth pollinated Hermaphrodite and male flowers, Mainly outcrossing 1,000 seed produced per tree

  14. Dovyalis caffra Bird?/insect pollinated Dioecious 270-470 seed produced per tree

  15. Sclerocarya birrea – male tree being cut as not producing fruits

  16. Grevillea robusta • Self incompatible with protandry • Fruit set cross-pollination (5.9-17.5%) >open-pollination on farms (0.1%-3.3%) • Open-pollinated flower stigmas – most no pollen or only self-pollen • Lack of cross-pollen may limit seed production

  17. Senna siamea • Insect pollinated • Hermaphrodite • Self–compatible? • High seed production per tree

  18. Procurement pathways NGOs compared with CBOs

  19. Distribution pathways

  20. Think about and discuss • Where are bottlenecks to genetic diversity? How to overcome these? • In 5 main species, how does seed production per tree influence number of trees seed collected from? How species biology affects genetic diversity in seed collections? • How can mixing seed ensure use and maintenance of existing genetic diversity? mean Ns/Nc vs mean Ns/Nm. • Advice/training to improve situation? Figs 2-4; to NGOs and/or directly to communities? What specific advice/training? • How does seed collection and plant production occur? • Are seeds and plants transferred and if so how? Does this provide limitations or opportunities?

  21. Plan objective: ensure maintenance of genetic diversity in the collection & supply of seed, & improved nursery practice • Plan should identify: • influences on genetic diversity(bottlenecks, selection, genetic drift) associated with current seed collection and distribution paths • key actors (individuals, institutions), processes (what actors do), social limits in seed supply chain (policy, trade, institutional, capacity). Communication/training needs related to key actors. • Specific actions to improve situation, addressing diversity issues in seed system (e.g. practical ways to collect & distribute seed/seedlings to ensure genetic diversity in nurseries & material planted in field)

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