Fertility Variation and Gene Diversity in Seed Crops of Eucalyptus and Casuarina Seedling Seed Orchards in Southern India Kamalakannan, R 1, Varghese, M 1, Chezhian, P 2, Ghosh, M 3. & Lindgren, D 4 1. ITC R&D Centre, SP Biotech Park, Turkapally, Shameerpt, Hyderabad , India 2. Tamilnadu News Print and Papers Ltd, Kagithapuram, Karur , India 3. Institute of Forest Genetics and Tree Breeding, P.B. No. 1061, Coimbatore , India 4. Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, SE , Umeå, Sweden Background Seedling seed orchards (SSO) are used as production populations in short rotation eucalypts and casuarina in India because of easy establishment and early seed production (Eldridge et al., 1993). The flowering pattern varies in seed orchards depending on the species, environment, age, developmental stage and management practices. Fertility variation can be estimated based on fecundity of individual trees. Gene diversity of seed crop is influenced by differences in fertility among parents and their relatedness (Kang et al., 2003). References: Eldridge, K. G., J. Davidson, C. E. Harwood and G. Van Wyk (1993): Eucalypt Domestication and Breeding,Clarendon Press, Oxford Lindgren, D. and T. J. Mullin (1998): Relatedness and status number in seed orchard crops. Can. J. For. Res.28: 276–283 Kang, K. S. (2001): Genetic gain and gene diversity of seed orchard crops. PhD thesis, Department of Forest Genetics and Plant Physiology, SLU, Umeå. Kang, K. S., A. D. Bila, A. M. Harju and D. Lindgren (2003): Estimation of fertility variation in forest tree populations. Forestry 76(3): 329–344 Materials and Methods Four seedling seed orchards each of Eucalyptus (two each of E. camaldulensis and E. tereticornis) and Casuarina (two each of C. equisetifolia and C. junghuhniana) located at climatically different sites in southern India were evaluated at four years for fertility variation and its impact on the seed crop. The theory developed by Lindgren and Mullin (1998) and Kang et al. (2001) for seed orchards was used for this study. Diversity of the seed orchard crops was compared with that of natural provenances and local land race seedlots using DNA (Inter simple sequence repeat) markers. Table:2. Fertility variation and population size in four casuarina SSOsTable:1 Fertility variation and population size in four eucalypt SSOs Results:  Less than 30% trees flowered in Eucalyptus orchards, except in one orchard which had 73% flowering trees.  The sibling coefficient (ψ) in eucalypt orchards varied from 2.2 to 17.4 and effective population size (N r ) varied from 0.45 to 0.06 (Table. 1).  Casuarina orchards had high fertility with more than 80% fertile trees, except in one C. junghuhniana orchard which had only 45% flowering trees.  Fertility variation in Casuarina was higher in the inland location (ψ=5.8 & 7.6) compared to the coastal site (ψ=2.7 & 2.9). N r ranged from 0.17 to 0.36 (Table.2).  Eucalyptus seed orchard crops had greater diversity (26.1 to 30.7% polymorphic loci) than a bulk seedlot of natural E. camaldulensis provenances (17.9 %).  In Casuarina, the % polymorphism in the orchard seedlots varied from 8.3 to 29.9% (Fig.3).  Local land races had lower molecular diversity than orchard seed crops in both genera.  Remarkable genetic differentiation and low levels of gene flow was detected in native provenances due to geographic isolation.  There was low genetic differentiation between seed orchard crops.  Natural provenance seedlots of both genera grouped independently (Fig.5 &6), which emphasizes the need for adequate isolation distance when relevant. Fig :3 Molecular diversity (% polymorphism) in SSO, native and landrace seed sources of Eucalyptus and Casuarina Fig:2. C. equisetifolia seedling seed orchard seed at inland site (SSO1) Fig:1 E.camaladulensis seedling seed orchard (SSO1) Fig:4 ISSR gel profile of Eucalyptus seed sources Fig:5 PCA of Eucalyptus seed sources Fig:6 PCA of Casuarina seed sources