Fertility Variation across Years in Two Clonal Seed Orchards of Teak and its Impact on Seed Crop. A. Nicodemus 1* , M. Varghese 1 , B. Nagarajan 1 and D. Lindgren 2 , 1 Institute of Forest Genetics and Tree Breeding, PB 1061, Coimbatore 641 002, Tamil Nadu. India 2 Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, SE-901 83 Umeå, Sweden. *email:nicodemus_a@rediffmail.com Introduction Teak (Tectona grandis L.f.) is a highly valued timber species raised in plantations throughout the tropics. Clonal Seed Orchards (CSO), established through grafts of selected trees are considered to be channels of genetically improved seed and starting point for domestication. India has over 1000 ha of CSOs but seed production from them has been too low to make any impact on the new plantations or advancing the breeding cycle. Genetic improvement of teak has not moved beyond the first generation orchards during the last 50 years. Reproductive biology of teak and in particular the causes for low seed production in orchards has been intensively studied during the past decade. Teak is a predominantly outcrossing species and insects are the major vectors of pollination. Absence of flowering, clonal variation in flowering phenology and pollinator limitation are reported to be the major reasons for low seed output (Nagarajan et al. 1996; Palupi and Owens, 1998; Gunaga and Vasudeva, 2002). The objectives of the present study were to quantify flower and fruit production in two orchards during consecutive years, to estimate fertility variation and its impact on the seed crop and to determine the factors that influence fertility status of orchards. Orchard Details and Study Methods Flower and fruit production was estimated during four consecutive years (2003-06) in two orchards located at Topslip (CSO I: 10˚ 25’ N, 76˚ 50’ E; rainfall: 2080 mm) and Walayar (CSO II: 17˚ 40’ N; 81˚ 00’ E; rainfall: 1000 mm). CSO I has 15 clones and CSO II 20 clones and 13 clones are common between them. Both the orchards were established in 1976 in a completely randomized design at a spacing of 5 m. Two thinnings were undertaken in the orchards which resulted in an average spacing of 10 m between trees. During the study period CSO I had 175 trees comprising 6 to 9 ramets each of 15 clones and CSO II had 454 trees represented by 13 to 30 ramets each of 20 clones.