Genetic Analysis For Agronomical Traits And Chemical Constituents In The Flue-cured Tobacco (Nicotiana Tobacum)

14 flue-cured tobacco varieties (or breeding lines) were crossed in a diallel mating design with unbalanced data to generate 41 F1 crosses. By randomized complete block design, parents and their F1 crosses were grown in four environments with two replications at each environment in Yunnan in 2002. Agronomy traits measured were plant height, girth of stem, internode length, number of leaves per plant, length of the middle leaves, width of the middle leaves. Yield, percent total sugar, percent reducing sugar, sugar different between percent total sugar and percent reducing sugar, percent total nitrogen, percent nicotine, percent protein and percent K2O were evaluated on the cured leaves. A genetic model including additive and dominance effects and their interaction with environments were applied for genetic and correlation analysis. Multivariable conditional analysis for the estimation of conditional variation and conditional genetic effects were used for genetic contribution analysis of agronomic traits to yield and chemical constituents. The main results were as follows:1. Additive, dominance, additive × environment interaction and dominance × environment interaction effects appeared to play roles in the inheritance of the agronomic traits measured. Additive main effects were the major genetic component for plant height and internode length. Number of leaves and length of leaves were mainly controlled by dominance × environment interaction effects. Additive × environment interaction effects and dominance × environment interaction effects played a major role for girth of stem. Yield performance was mainly controlled by additive effects and dominance × environment interaction effects. The additive effects of plant height and internode length were mainly dependent on the additive main effects. The additive effects of number of leaves, length of middle leaves, width of middle leaves and yield were mainly dependent on additive main effects, and affected by the additive × environment interaction effects to some extent. The additive effects of girth of stem were mainly dependent on additive × environment interaction effects. With regard to most agronomic traits, the breeding line P14 developed in Yunnan performed high positive additive effect, and the varieties P12 and P8 derived from northern China had high negative additive effects. Dominance effects and the dominance × 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.2. Additive, dominance, additive × environment interaction and dominance × environment interaction gene action were of importance to the inheritance of chemical constituents evaluated. Percent nicotine was mainly controlled by the additive main effects. Dominance × environmentinteraction effects played a major role for total sugar, reducing sugar, sugar difference, total nitrogen, protein and K2O, while the additive main effects played considerable role in the inheritance of reducing sugar, total nitrogen and K2O. For total sugar and reducing sugar, the varieties (or breeding line) such as P4, P7 and P14 developed in Yunnan performed significantly positive additive effects, and the varieties P12 and P8 in northern China had significantly negative additive effects. The parents which had positive additive effects for total sugar and reducing sugar tended to have negative additive effects for total nitrogen and nicotine. No parents and F1 crosses investigated performed negative effects for sugar difference and nicotine and positive effects for K2O.3. The analysis of correlation among agronomic traits revealed that most of phenotypic, genotypic, additive and dominance correlations were positive. The trait pairs with additive correlation coefficients more than 0.5 were plant height and internode length, girth of stem and internode length, internode length and width of middle leaves, plant heigth and width of middle leaves, girth of st...