Sorghum is a major staple food crop for the people in semi-arid areas of Asia. Post-flowering drought is a global constraint of sorghum production with this the present study is to study the genetics of stay green and yield traits to the drought stress tolerance of the stay green introgressed lines. The significance of scaling test except for traits days to flowering for the traits studied indicates that the simple additive - dominance model or simply additive model is not adequate to explain the gene effects of stay green and grain yield component traits in sorghum. This result shows that traits presence of non-allelic interaction controlling these traits. With respect to stay-green, comparison between generation means revealed non-additive gene action for trait inheritance of stay green traits. The predominance of mean effect, dominance and dominance × dominance gene effects indicating dominant gene action play major role controlling the SPADB, SPADM, total number of green leaves at booting and maturity, green leaf area at booting and maturity in both crosses studied. With respect to gene effects mean followed by dominance and additive × dominance gene effect is significant and predominance in controlling the trait. However, the dominance and additive × dominance gene effect are in negative direction in both the crosses. The non-allelic gene action shows duplicate gene interaction. Duplicate epistasis signifies dispersion of alleles at the interacting loci and will decrease variation in S2 or F2 and subsequent generations and will delay the pace of progress through selection.

Drought Stress, Stay Green and Yield traits

The dominant gene action is significant and predominant for canopy temperature and leaf temperature in both crosses and also the F1 mean of both the crosses on par with the better parents (K260 and K359w) indicate dominant genes play role in trait expression. Photosynthetic rate at booting and maturity the mean of F1 generation for the trait on par with the better parental means of K260 and K359w indicating presence of dominant gene action in the both the crosses GS-23×K260 and GS-23 × K359w. For PRB, apart from mean effect, dominance and additive × dominance gene effects are significantly predominant among all the gene effects. With respect to grain yield component traits scaling test revealed presence of epistasis for all the traits except days to 50% flowering. Days to booting all the gene effects were significant in cross 1 (GS-23 × K260). With respect to gene effects additive, dominance, additive×dominance and dominance×dominance effects were significant indicate their predominant role in controlling the trait. Days to maturity, duplicate epistasis involved in the controlling of the trait in the cross GS-23 × K260 and complementary epistasis involved in the controlling of the trait in other cross GS-23 × K359w. Plant height, panicle length and panicle width, the mean of F1, BC1 and BC2 generation is more inclined toward the better parents indicating the trait is under control of dominance gene action. Further, the dominance and dominance×dominance gene actions are predominant in trait expression and they are under duplicate epistasis. Grain yield per plant with respect to gene effects, except additive gene effect, all other gene effects are significant in first cross (GS-23 × K260) and mean effect followed by dominance and dominance × dominance gene effects are predominant in controlling the trait. Whereas in second cross additive and additive × dominance gene interaction is non-significant (GS-23 × K359w) and mean effect followed by dominance and additive × additive gene effects are predominant in controlling the trait. The additive × dominance is significant and the value is near to the mean indicating the major involvement of additive × dominance gene effect in trait expression of fodder yield per plant. Thousand seed weight and grain number per panicle all the gene effects are significant with predominance of dominance and dominance × dominance gene effect with opposite sign values indicating duplicate epistasis involved in trait expression. For harvest index per panicle mean and all gene effects are significant dominance mean and additive × dominance are predominant in trait expression. Whereas in the second cross (GS-23 × K359w), dominance, mean and dominance × dominance is predominant in trait expression. Leaf colour was controlled by two dominant independent genes viz., Dg1 and Dg2. Whereas stay green trait was controlled by two independent dominant genes STG3A and STG3B. Stay green inheritance studies in F1, F2 and F3 breeding behavior showed that the dominant gene action plays major role in controlling the stay green trait in both the crosses and stay green trait is dominant across generations in nature of expressing at maturity level too, thus giving the sorghum crop to with stand physiological stress under drought conditions by staying green.

Priyanka S., Girish G., Lokesha R., Tembhurne B. V., Amaregouda Patil and Ayyanagouda Patil (2023). Genetics of Physiological and Yield Traits of Stay Green in Sorghum to Drought Stress in Rabi. Biological Forum – An International Journal, 15(8): 90-105.