Interaction Effects of General Combining Ability and Specific Combining Ability with Environment in Virginia Tobacco Genotypes

To evaluate the effect of environment on the general and specific combining ability of Virginia tobacco genotypes, five varieties were intercrossed in combination in 2007 in a Half – diallel design. In 2008, the ten F1 population and the five parental lines were sown in two different conditions (drought stress and non-stress) using a complete randomized block design with three replications and two locations (Tirtash and Rasht Tobacco Research Center). The studied traits were: leaf length, leaf width, leaf numbers per plant, leaf area index, plant height and dry leaf yield. Dialle analysis in all environments revealed interactions of GCA×E for most traits, emphasizing the importance of calculation of effects for each environment separately. SCA×E was highly significant for all traits except for the chlorophyll content and leaf area index, indicating that the specific hybrids weren’t stable across the environments. The significant interactions indicated that the magnitude of differences among GCA and SCA effects of genotypes changed with environment. In general, the GCA/SCA ratio over all environments was significant for all quantitative traits except for leaf length, indicating the predominant role of additive genetic effects in the inheritance of most traits. The cultivars NC89 and k394 were the best general combiners, while NC89×k394, VE1×Coker254, Coker347×Coker254 were the best specific combinations for dry leaf yield over all investigated environments.