Annual Fertility Variation in Clonal Seed Orchards of Teak (Tectona grandis L.f.) and its Impact on Seed Crop

Fertility variation was studied in two clonal seed orchards (CSO) of teak in four consecutive years (2003-2006). Both orchards were raised in 1976 with grafts of phenotypes selected for growth and form. The seed orchards of CSO I (Topslip, Tamil Nadu State) and CSO II (Walayar, Kerala State) have 15 and 20 clones, respectively, with 13 common clones. The proportion of flowering ramets was generally low ranging from 16 to 53% across years. The best fruit yield during the study period was around 18 kg ha-1 in CSO I and 17 kg ha-1 in CSO II. Highly significant clonal variation and clone by year and clone by site interactions were observed for fertility traits. The clonal contribution was more skewed in poor flowering years than in abundant flowering years and in CSO II than in CSO I. Broad sense heritability for flower and fruit production per tree was low to moderate (0.16 to 0.55). Flower and fruit production by individual ramets in successive years were positively correlated. Correlations between reproductive and growth traits were generally low, but correlation was strong between flowering and fruiting. Fertility variation and group coancestry were higher in poor flowering years than in abundant years and in CSO II than CSO I. Restricting seed collection to abundant flowering years, adjusting ramet number to balance contribution of clones and mixing of seeds from successive years are suggested to reduce relatedness among orchard progeny. The usefulness of low input breeding options for teak like seed production areas are also discussed.