Fertility variation and its implications on relatedness in seed crops in seedling seed orchards of Eucalyptus camaldulensis and E-tereticornis

Seedling seed orchards of Eucalyptus tereticornis (N=192 & 505) and E. camaldulensis (N=182 & 525) were established at two sites (one moist and one dry) in southern India. The fertility (based on the number of flowers and fruits) was registered for each tree at age eight and nine years. E. camaldulensis on the moist location had 73 % fertile trees and low fertility difference (sibling coefficient, T, was 2.27) at eight years. whereas Only 23% trees were fertile in the E. tereticornis orchard at the same site and the fertility variation was high (Psi= 11.71). In the dry location, fertility was almost the same in both species at nine years, with 45 & 51% fertile trees in E. camaldulensis (Psi = 5.4) and E. tereticornis (Psi = 5.2) respectively. Though the fertility trends were the same in both years, the number of fertile trees was comparatively higher at nine years (except in the low flowering E. tereticornis orchard at the moist site) in both the sites. Gene diversity values of the seed crop estimated for two consecutive years are fairly high except for the E. tereticornis (GD=0.9650 and 0.9690) orchard located in the moist site. The implications of fertility variation on diversity of progeny have been discussed in the light of domestication strategies and tree breeding programs implemented for eucalypts.