Abstract: Chemical constituents are the major factors attributed to leaf quality in the flue-cured tobacco, and are sensitive to environments. Despite inheritance of some chemical characteristics was reported, information on genotype by environment interaction is generally lacking. The objectives of this research were to evaluate the genetic effects for chemical constituents, and to understand the genetic correlations among the traits analyzed. By using randomized complete block design, 14 flue-cured tobacco cultivars(or breeding lines) and their 41 F₁ crosses were grown in four locations with two replications at each location in Yunnan Province in 2002. Percents of total sugar, reducing sugar, sugar difference between percents of total sugar and reducing sugar, percents of total nitrogen, nicotine, protein and K₂O were evaluated for the cured leaves. A genetic model including additive and dominance effects and their interaction with environments was applied for genetic and correlation analyses. Additive, dominance, additive by enviroment interaction and dominance by environment interaction genetic effects appeared to play an importance role in the inheritance of additive variance to phenotypic variance was 0.302(See in Table 1). Dominance×environment interaction effects played a major role for total sugar, reducing sugar,sugar difference, total nitrogen, protein, and K₂O. No parents and crosses investigated had negative effects for sugar difference and nicotine, but positive effects for K₂O.The analysis of correlation among chemical constituents revealed that there were positive correlations of phenotypic, genotypic and additive effects among the nitrogenous compounds such as total nitrogen, nicotine, protein, and negative correlation with total sugar and reducing sugar for phenotypic, genotypic and additive effects. Sugar difference, nicotine and K₂O had low or no correlation with each others(Table 4). The predominance of additive genetic variance for nicotine in this study suggests that the most effective breeding procedures for improving nititine content will be those which lead to the superior homozygous lines. The predominance of dominance by environment interaction variance for those which lead to the superior homozygous lines. The predominance of dominance by environment interaction variance for sugar difference and K₂O percent suggests that the utility of heterosis should be considered in specific environments. It is possible to decrease sugar difference and nicotine, and increase K₂O simultaneously in tobacco leaves by making more crosses or enlarging offspring population.

Key words: Flue-cured tobacco, Chemical constituents, Additive-dominance model, Genotype by environment interaction