Analysis of Genetic Effects of Chemical Components in Flue-cured Tobacco

In order to breed new flue-cured tobacco lines of harmonious chemical composition via scientific and rational parent selection and combination collocation, thirty complete diallel cross combinations were prepared from six flue-cured tobacco varieties with Griffing method (Ⅲ). The genetic effects of eight chemical component indexes (the contents of nicotine, total nitrogen, total sugar, potassium, chlorine and the ratios of total nitrogen/nicotine, total sugar/nicotine, potassium/chlorine) in tobacco leaves were preliminarily analyzed. The results showed that the said chemical indexes differed extremely significantly between combinations, the general combining ability (GCA) between parents and the specific combining ability (SCA) between combinations exhibited extremely significantly differences as well. Moreover, the variance of GCA was greater than that of SCA for all the indexes except for the ratio of total nitrogen/nicotine. It indicated that for most of the chemical indexes investigated in this experiment, parent selection was more important than combination collocation. For GCA effect, cv. RG17 possessed a potential in increasing potassium content and cv. Nanjiang No.3 might increase potassium/chlorine ratio; 6388 lines presented a potential in decreasing chlorine content. Analyzing SCA effect from the point of chemical quality, the combination of K326 ×Nanjiang No.3, Jingyehuang × Nanjiang No.3 and K8 × Jingyehuang were the best, followed by K326 × Jingyehuang and K8×RG17. There existed obvious heritability differences between the traits of chemical indexes. Potassium content and total sugar content possessed the highest and the lowest special heritability of 33.82% and 1.37%, respectively. The general heritability of chlorine content (51.84%) and potassium content (50.04%) was the highest, while that of total sugar content (15.08%) was the lowest. Only the special heritability of potassium content accounted for over 50% of general heritability, it indicated that the heritability of potassium content mainly was additive effect, which facilitated to the breeding tobacco cultivars of high-potassium content and was suitable to line selection at earlier generation. For the traits of other chemical indexes, it would be preferable to carry out line selection while the trait became stable.