Quantitative Inheritance And It's Interaction With Environment For Main Chemical Quality Trait In Flue-crued Tobacco

Six parental flue-cured tobacco varieties(lines)were used for diallel cross based on {p·(p-1)/2} design to get genetic materials including parental lines and two generations of F₁s.The data of main quality traits were collected from 2-year results conducted in 2005 and 2006.The dynamic inheritance of main quality traits in flue-cured tobacco at different leaf stages was analyzed using additive-dominant developmental genetic model.Unconditional genetic variance as a method of traditional genetic analysis only provides the total accumulated genetic effects of all genes expressed before each growth period,such as the phase from(t-1)to(t-1→t).Conditional genetic analysis can be used to determine the net effect between two adjacent developmental stages,and explored the dynamic inheritance performance in a given time(t-1→t)without the interference in previous growth stages. Based on experimental data at different developmental stages,estimates of genetic effects for total sugar,total nitrogen,nicotine,ratio of sugar to nicotine,ratio of nitrogen to nicotine,and Schmuck value of flue-cured tobacco at the developmental stages(0→13-leaf)or the special developmental periods(7|5,9|7,11|9,13|11)under the consideration were conducted using additive-dominant genetic model and developmental genetic model for quantitative traits.Analysis of unconditional genetic variance revealed that the six quality traits of flue-cured tobacco in the testing time courses,were mainly controlled by the interaction of dominant effects with environment.The additive effects on those quality traits were very low,and the dominant,and the dominant effects on the traits showed much lower,in the same phase. However,in terms of the growing stages,the higher dominant and additive effects were detected at the 7～11 leaf stages,suggesting that the selection for the uilzation of heterosis would be effective in these stages,in which time the effect of environment on heterosis in the tobacco should be paid attentionAnalysis of conditional genetic variance indicated that the same tendency was also found in the genetic performance of the six traits as mentioned earlier,showing that the traits were expressed significantly mediated by the interaction of dominant effects with environment but slightly by additive gene effects,suggesting that the utilization of heterosis would be effective in the improvement of the tobacco quality,but the environmental effect on heterosis should be also paid attention.The results form unconditional heritabilities analysis suggested that the expression of genes for six quality traits were significantly affected by environment,suggesting the selection for that the quality of flue-cured tobacco could be mediated by cultivature practiceAnalysis of genetic covariance proved that genetic covariance was positive or negative to different degrees between different leaf stages and different quality traits.Based on genetic relationship controlled by different genetic systems and desirable range of the traits concerned,different methods were determined in breeding program,in this way the breeding objective of increasing or decreasing the different qualities in the main traits of flue-cured tobacco would be realized.Based on analysis of the genetic effect covariance for flue-cured tobacco at different main quality traits of flue-cured tobacco,it indicated that increasing total sugar apparent to increase the nicotine,ratio of sugar to nicotine and Schmuck value,but to decreased total nitrogen.Negative effect was found in the correlated direct additive correlation(CorA)of total nitrogen and the other traits,the decreased total nitrogen might lead to the decreases of nicotine,ratio of sugar to nicotine and Schmuck value,implying that it appeared to be effective to improve traits at the given time.The analysis of the correlation between the direct dominant covariances(CovD)of total nitrogen and the other traits showed that it appeared to be effective in hybrid breeding.The correlation were positive,between the direct additional covariance(CovA)in nicotine and the other traits implying that it would be effective to improve nicotine content,ratio of sugar to nicotine and Schmuck value,but negative between nicotine and the ratio of nitrogen to nicotine,suggesting that it was difficult to improve them at the given time.The analysis of correlation between the direct dominant correlation(CorD)of nitrogen and the other traits showed that it appeared to be effective in hybrid breeding.Negative effect was found in the correlation between in direct additive covariances(CovA)of ratio of sugar to nicotine and ratio of nitrogen to nicotine,but positive effect was found in sugar,nicotine and Schmuck value,implying that it appeared to be effective to improve the traits.The correlation between direct dominance covariances(CovD) of ratio of sugar to nicotine and Schmuck value showed that it appeared to be effective to use heterosis in breeding.Direct additive correlation(CorA)between ratio of nitrogen to nicotine and Schmuck value showed that it appeared to be effective to improve traits.negative effect was found in direct dominant correlation(CorD),implying that it was hard to be successful in heterosis breeding.