genetic improvement of ash in british forestry: floral diversity of ash- fraxinus excelsior jo clark...
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Genetic improvement of ash in British forestry:
Floral Diversity of Ash-Fraxinus excelsior
Jo Clark
National School of Forestry
University of Central Lancashire
Introduction
UK lowest forestry cover in Europe except Ireland (11%)Shift away from coniferous plantations to broadleaves, higher grant ratesInflux on non native, non adapted materialAsh is second most commonly planted hardwood Prone to forking and poor form without proper silvicultureNeed for tree improvement on hardwood speciesReduction in rotation time and better form
Problems With Growing Quality Ash
Ash bud moth Prays
fraxinella
Ash canker Nectria
galligena
Frost damage
Set up in 1991 to improve the quality of planting stock available to the forester
Comprised of landowners, academics and interested parties
Preferred improvement technique that of the Breeding Seedling Orchard – BSO (Barnes 1995)
BIHIP – The British and Irish
Hardwood Improvement Programme
Stages in a Traditional Tree Improvement
Programme
1. Identification of phenotypically superior (plus) trees
2. Collection of reproductive material – either seed or scion
3. Establishment of progeny trials4. Selection of best performing
individuals for seed orchard establishment
5. Orchard of ‘improved’ seed bearing trees
Traditional Vs BSO Approach
Plus Tree Selection
BSOProgeny Trial
and Seed Orchard
20 Years
Improved Seed in 20
Years
Plus Tree Selection
Progeny Trial
Seed Orchard of Proven
Individuals20
Years
20 Years
Improved Seed in 40
Years
Plus Tree
Selection
Ash BSO Design and Layout
36 families of half sibs
4 orchards of replicated units varying from
720 to 1296 trees
Randomised block design with double buffer
row
Not all families are present in each orchard
4264 trees in total
BSO Assessment:Form
Major Kink
Classic Fork
Severe Sweeps
Perfect Tree
Mean Height of Families Recorded at Four BSOs in
2001
100.00
150.00
200.00
250.00
300.00
350.00
400.00
450.00
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Family
Hei
ght (
cm)
Little Hidden Farm
Mulgrave
Little Wittenham
Scarr
1 2 4 5 9 10 12 13 14 16 18 20 21 22 25 26 33 34 35 36
1
4 5
9 20 22 34 36
33
Family Performance for Height
0
50
100
150
200
250
300
350
400
450
30 19 34 23 17 1 36 10 15 13 9 14 7 20 21 26 22 6 18 11 2 12 25 33 35 8 24 31 16 29 4 28 5 3 32 27
Family
Hei
ght
(cm
)
Ht 1996 96-98 98-2001
What to Rogue?
How many trees should be left?
Should we select individual trees, ie,
the top 150 individuals?
Or should we select the top families?
What about gender?
Genetic Gain Calculations for Height
Top 150 trees
Top 150 trees of 20 common families
Top 30 families
Top 10 families
Top trees of top 30 families
Scarr 44.8 33.5 1.4 10.85 40.12Mulgrave Estate 7.25 7.25 0 0.95 7.2Little Wittenham 28.89 9.9 1.62 6.75 26.19Little Hidden Farm 24.3 9.36 0 5.94 21.6
Scarr = 32 familiesMulgrave Estate = 21 familiesLittle Wittenham = 36 familiesLittle Hidden Farm = 27 families
Floral Biology of Ash
Wind pollinationA polymorphous species exhibiting a continuum of gender
Staminate flowers
Pistillate flowers
True Hermaphrodite
Hermaphrodite Flowers
Anther
Filament
Stigma
Style
Predominantly hermaphrodite flowers with some pure male inflorescences
Predominantly Male Flowers
Predominantly Female Flowers
Male Inflorescence With the Terminal Flower
Female
Seed Development
Questions Pertaining to Gender
1. What proportion are male and female?
2. Do they change sex as they age?
3. Are male trees bigger than female trees?
4. On a hermaphrodite, do male flowers appear earlier than female to prevent self pollination?
5. Do female trees show a higher degree of forking?
6. How much seed does a true hermaphrodite produce?
Flower Ratios Recorded at the
Scarr BSO in 2002 and 2003
0%
4%
32%
57%
7% 9%
8%
31%39%
8%5%
Female
Female (h)
Hermaphrodite
Male
Male + h
Male (t)
2003
589 trees
2002
170 trees
Gender Answers
Average height of all females = 414cmAverage height of all males = 410cmMale flowers appear up to one month earlier than female flowers preventing self fertilisationAverage forks per female tree = 0.97Average forks per male tree = 0.80Huge variation in seed production by hermaphrodites