Studies on heterotic parameters in Populus deltoides

Exploitation of genetic variability of Populus deltoides Bartr. through control crossing involving Line x Tester mating design was attempted with the objective of selection of suitable clones as well as parents for hybridization in future and identification of best families and best individuals with in family for releasing first stage clones. Lines ST-72, D-121, G-48, exhibited the highest positive GCA effects for plant height, collar diameter, plant height at first branch and root length. In general G-48 also proved to be the best combiner for survival percentage, inter nodal length and leaf area. Among the testers ST-63 and ST-70 expressed highest GCA effects and excelled for a number of desirable characters. Full sib families (F₁s) of D-121 x ST-70 and G-48 x ST-63 showed desirable SCA for plant height and collar diameter and therefore F₁ hybrids of these crosses are recommended at first stage of selections. The percent contribution of line x tester interactions was higher than that of lines and testers except number of leaves per plant. 13 traits expressed higher SCA variance than GCA variance and dominant gene effect (σ²D) were found higher than additive gene effect (σ²A) except in root length. For recurrent selection based on GCA effects, parents G-48, ST-70, D-121 and ST-63 appeared more appropriate in crossing programme directed towards clonal improvement of Poplar in India.