Mohan Varghese 1, 2 , N. Ravi 2 , Seog-Gu Son 1, 3 and Dag Lindgren 1

1. Variation in fertility and its impact on gene diversity in a seedling seed orchard of Eucalyptus tereticornis • Mohan Varghese 1, 2, N. Ravi 2, Seog-Gu Son 1, 3 • and Dag Lindgren1 • 1 Swedish University of Agricultural Sciences, Umea, Sweden • 2. Institute of Forest Genetics and Tree Breeding, Coimbatore, India • 3. Korea Forest Research Institute, Cheongryangri, Seoul, Korea

2. Introduction • Progeny trials • Serve as breeding populations in short rotation eucalypts • Enables testing of fullsib and half sib families – heritability and breeding values • Thinning and conversion to SSOs

3. Domestication of E. tereticornis • Indian land race – Mysore gum has narrow base, inbred and suffers hybrid breakdown • Breeding populations of natural provenances and local selections • Poor flowering of natural provenances in South India.

4. Study Material • First generation open pollinated progeny trial – 42 families of 17 provenances, 24 trees per family, 4 tree plots, incomplete block design. • Perfect flowers in umbels of 5-7/cluster. • Outcrossed with protandrous flowers, pollination could occur between flowers of a tree or between related trees.

5. Assessment • Breeding values estimated from combined index values. • Number of primary, secondary and tertiary branches and number of flowers and fruits recorded for each tree • Flowers per tertiary branch and stamens per flower recorded in 10 flowers per tree • Fruits per secondary branch recorded

6. Fertility estimation • Male and female fertility assumed to be equal to number of male and female gametes produced by a tree • Gender fertility assumed to be equal to proportion of reproductive structures of a tree • Total fertility of a tree – average of male and female fertilities.

7. Conversion to SSO • Trees listed according to phenotypic value for tree height. • Hypothetical truncation of 20% best trees (200 trees) to be retained after thinning based on deviation of individual tree value from overall mean

8. Sibling coefficient (A) • Indicates the extent of variation in fertility • Calculated from number of trees in the orchard (N) and fertility of each tree (pi) • A =N Σpi2 • Am =N Σmi2 • Af =N Σfi2

9. Group coancestry (Θ) • The probability that two genes chosen at random are identical by descent. • Θ = 0.5Σpi2 - if the trees are non related and non inbred • Θ =ΣΣpi pjθij - pi pj – probability that genes originate from genotypes i and j;θij the coancestry between i and j

10. Different sexes of parents • Θ =Σ(mi+fj)Σ (mj+fj) θij probability of maternal and paternal fertility and an interaction component are considered.

11. Status Number (Ns) • The number of unrelated and non inbred genotypes in an ideal panmictic orchard – same coefft. of inbreeding in crop as orchard parents. • Ns = 0.5/ Θ • Ns = 1/Σpi2 – if the trees are unrelated – the effective population size • The effective number of trees that contribute to random mating.

12. Variance effective population size (Ne(v)) • The size of the population that would give same drift in gene frequencies in seed crop as orchard parents. • Ne(v) = A / [2 Θ(A-1)]

14. Predicting relatedness across generations • Θ gamete is a function of inbreeding (F), fertility variation (A) and number (N) of parent trees • Θ offspring= 0.5/Noffspring+(1-0.5/Noffspring )Θ gamete • Θ gamete =[ 0.5(1+F)A/N ] + (1-A/N)[ NΘ-0.5(1+F) ] / N-1 • Foffspring = Θ gamete

15. Gene diversity (GD) and Heterozygosity (He) • Reference population – natural forest is considered to have infinite number of unrelated individuals. • GD = 1- Θ • Het = [1-(1/2Ne(v) )] Het-1

16. Genetic gain • Expected genetic gain is computed based on fertility of orchard parents and breeding value of trees. • ΔG = ΣGi pi

17. Fertility status • 18% ( 35 trees) of selected trees were fertile • No correlation between tree growth and fertility (r = 0.057) • High correlation between male and female fertility (r = 0.981) • Greater variation in seed output than in pollen production between trees

18. Variation in A

19. Varying fertility

20. Constant seed collection

21. Extra male parents

22. Altering fertility status • Constant seed collection –lowers Θ by 92% in 7th generation and Ne(v) is twice that of existing fertility. Minimum loss in diversity in each generation • Extra pollen parents – 14% reduction in Θ in7th generation. 4-7% reduction in loss of diversity from existing fertility.

24. Impact of fertility status • Important role as breeding value as it transfers the genes to the seed crop. • Fertility in trees varied from 0-20% (0.005% if trees had same fertility) • 12 most fertile trees • produced 81% of gametes • A=17.4 results in high • genetic erosion (Nr drop • from 4.3% to 0.9%) in 7th • generation)

25. Emphasis in first generation seed orchard of exotics • Initiates domestication in a new location • Lower the values of A to prevent genetic erosion ( 17.4 > reported value A=9.32) • Enable random of maximum trees of known genetic potential. • Limit equal seed collection to genetically superior mothers and provide adequate male parents to enhance the gene diversity.

27. Conclusion • High levels of inbreeding and drift may result if precautions are not taken in a first generation orchard • An SSO is ideal in initiating a breeding / domestication program as seed can be produced for different requirements. • Additional pollen parents can be retained till selected • trees contribute seed. • Paclobutrazol can be used to enhance flowering.

28. Paclo application in E.camaldulensis Paclo application in E.tereticornis