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 Lindgren 1 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

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

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.

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.

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

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.

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

Sibling coefficient ( A ) Indicates the extent of variation in fertility Calculated from number of trees in the orchard ( N ) and fertility of each tree ( p i ) A =N Σ p i 2 A m =N Σ m i 2 A f =N Σ f i 2

Group coancestry ( Θ ) The probability that two genes chosen at random are identical by descent. Θ = 0.5 Σ p i 2 - if the trees are non related and non inbred Θ =Σ Σ p i p j θ ij - p i p j – probability that genes originate from genotypes i and j ; θ ij the coancestry between i and j

Different sexes of parents Θ =Σ(m i +f j ) Σ (m j +f j ) θ ij probability of maternal and paternal fertility and an interaction component are considered.

Status Number ( N s ) The number of unrelated and non inbred genotypes in an ideal panmictic orchard – same coefft. of inbreeding in crop as orchard parents. N s = 0.5/ Θ N s = 1/ Σ p i 2 – if the trees are unrelated – the effective population size The effective number of trees that contribute to random mating.

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

SSOM(Seeding Seed Orchard Manager) Input constant Realtedness within familiy Expectations of seed orchard RUN Number of trees Group coancestry;  =  ( m i +f i )  ( m j +f j )  ij =  p i p j  ij Status number;N s = 0.5 /  Sibling coefficient; A = C.V Variance effective population size; N e (v) =A/2  (A-1) Input measurements ProportionInput I.D B.V.fifi mimi pipi Family

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/ N offspring +(1-0.5/ N offspring ) Θ gamete Θ gamete =[ 0.5(1+ F ) A / N ] + (1-A/N)[ N Θ -0.5(1+ F) ] / N -1 F offspring = Θ gamete

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

Genetic gain Expected genetic gain is computed based on fertility of orchard parents and breeding value of trees. ΔG = Σ G i p i

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

Variation in A Fertility typeSelected 35 trees 70 pollen parents Male Female Av tree fertility Constant seed collection Equal fertility

Varying fertility Gen 1Gen 2Gen 4Gen 6Gen7 Θ NsNs GD

Constant seed collection Gen 1Gen 2Gen 4Gen 6Gen7 Θ NsNs GD

Extra male parents Gen 1Gen 2Gen 4Gen 6Gen7 Θ NsNs GD

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

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 7 th generation)

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.

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.

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