Upload
christina-casey
View
219
Download
0
Tags:
Embed Size (px)
Citation preview
Forest Genetic Resources Training Guide
Tree seed supply chains
Tree planting on farms in East Africa: how to ensure genetic diversity?David Boshier,Ian Dawson &Ard Lengkeek
Forest Genetic Resources Training Guide
Location of the countries and survey areas
KenyaUganda
Tanzania
Kabale
Mabira
Arusha
Meru
Nairobi
Location of nursery survey sites
Forest Genetic Resources Training Guide
Forest Genetic Resources Training Guide
Nursery sites
Forest Genetic Resources Training Guide
Why bother about genetic diversity?
• adaptation to changing environments• direct use of genetic resources• viability of populations in short term• - seed production• - inbreeding depression
Forest Genetic Resources Training Guide
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
Forest Genetic Resources Training Guide
Theory
• direct impacts
• decrease population size
• increase spatial isolation
• decrease densities
• change local environment
genetic processes
genetic drift
gene flow
mating - inbreeding
selection
Forest Genetic Resources Training Guide
Bottleneck genetic drift
Forest Genetic Resources Training Guide
Isolated trees– mating patterns?
Forest Genetic Resources Training Guide
Altered mating patterns in farm trees?
• Predictions: increased inbreeding• greater pollen dispersal• fewer sires
• Isolated farm tree Continuous forest
inbreedingdispersal
sires
Forest Genetic Resources Training Guide
How many trees to collect from?
Forest Genetic Resources Training Guide
Data collected in a survey of seed-propagated tree species in tree nurseries from five areas in East Africa
Survey area (country) All areas
Kabale (Uganda)
Mabira (Uganda)
Nairobi (Kenya)
Meru (Kenya)
Arusha (Tanzania)
Nurseries [client data*] 7 [6] 9 [7] 21 [16] 12 [8] 22 [22] 71 [59]Cases [client data] 15 [8] 26 [16] 31 [25] 17 [10] 54 [54] 143 [113]All species 11 14 16 7 16 43Indigenous species 3 6 6 1 3 15Cases indigenous species 4 10 6 2 5 27Cases five most common species
2 3 11 10 40 66
Cases of unique species occurrence
3 6 6 2 5 22
Single tree collections all species
7 4 8 7 5 31
Single tree collections indigenous species
2 1 2 0 1 6
Seed trees per nursery lot, Nm: mean (SD)
3.7 1.8 (3.6)
5.1 2.3 (6.0)
5.8 3.1 (8.9)
5.7 3.1 (6.5)
8.2 3.8 (14.1)
6.4 1.7 (10.3)
Seedlings per nursery lot, Ns: mean (SD)
871 712 (1408)
2060 1408 (3661)
787 432 (1228)
1339 1011 (2127)
1543 676 (2535)
1378 401 (2446)
Clients per nursery lot, Nc: mean (SD)
12 14 (20)
41 27 (55)
17 9 (22) 81 92 (149)
22 5 (20) 28 10 (53)
Forest Genetic Resources Training Guide
Forest Genetic Resources Training Guide
Cupressus lusitanica
Wind pollinatedHermaphrodite, self compatible100,000 seed produced per tree
Forest Genetic Resources Training Guide
Calliandra calothyrsus
Bat/moth pollinatedHermaphrodite and male flowers, Mainly outcrossing1,000 seed produced per tree
Forest Genetic Resources Training Guide
Dovyalis caffra
Bird?/insect pollinatedDioecious270-470 seed produced per tree
Forest Genetic Resources Training Guide
Sclerocarya birrea – male tree being cut as not producing fruits
Forest Genetic Resources Training Guide
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
Forest Genetic Resources Training Guide
Senna siamea
• Insect pollinated• Hermaphrodite• Self–compatible?• High seed production per
tree
Forest Genetic Resources Training Guide
Procurement pathwaysNGOs compared with CBOs
Forest Genetic Resources Training Guide
Distribution pathways
Forest Genetic Resources Training Guide
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?
Forest Genetic Resources Training Guide
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)