[Genetic and correlation analysis for agronomic traits in flue-cured tobacco (Nicotiana tabacum L.)].

By using a genetic model including additive and dominance effects and their interaction with environments, 7 agronomic traits were analyzed for a diallel design in 4 environmental conditions with 14 flue-cured tobacco varieties (or breeding lines) and their 41 F1 crosses. It was revealed that additive effects were the major genetic component for plant height, internode length, and width of leaves. Number of leaves and length of leaves were mainly controlled by dominance x environment interaction effects. Additive x environment interaction effects and dominance x environment interaction effects played a major role for girth of stem. Yield performance was mainly controlled by additive effects and dominance x environment interaction effects. The varieties adapted to local environments tended to have highly positive additive effects. Dominance effects and the dominance x environment interaction effects could perform differently in positive or negative direction for many crosses. The breeding program for hybrids should consider the adaptation of hybrids to specific ecological environments. The analysis of correlation among agronomic traits indicated that most of phenotypic, genotypic, additive and dominance correlation coefficients were positive. Additive correlations were predominance in genetic correlations for most pairs of traits. Yield can be improved by indirect selection on plant height.

[Genetic contribution of agronomic traits to yield in flue-cured tobacco (Nicotiana tabacum L.)].

In order to understand the genetic contribution of six agronomic traits to yield, 14 flue-cured tobacco varieties (or breeding lines) and their 41 F1 crosses were used for multivariable conditional analysis. The contribution of additive variance of plant height to yield was larger than other agronomic traits. The largest contribution of dominant variance to yield was due to the length of middle leaves. All agronomic traits investigated had small contribution to yield due to additive x environment interaction effects and dominant x environment interaction effects. No identical trait of different parents showed the largest contribution to additive effect of yield. This could be resulted from the fact that each parent had its own genetic and developmental characterization. The dominant effects of yield were mainly influenced by length of middle leaves in most crosses. Length of middle leaves could be served as ameasurement to indirectly select the cross parent having high dominant effect of yield.