Assessment of gene effects for drought and yield contributing traits in rice (Oryza sativa L.)
Abstract
Drought tolerance is a polygenic character controlled by polygenes and very difficult to study the gene action by line x tester analysis for improvement of drought related traits. In this situation, the present study was conducted to identify gene effects in rice for drought and yield contributing characters under drought condition by generation mean analysis. The six generations viz., P1, P2, F1, F2, BC1 and BC2 were generated in three crosses viz., PMK 4 x ADT 45, Norungan x ASD 16 and Nootripathu x Co 51. Moisture stress was imposed during 30 days after planting by withholding irrigation. During drought period, the condition of the soil was dry and fragmented. Data on yield and drought contributing traits were recorded for all six generations. The results revealed that, among the main genetic effects, dominance was positively expressed in all characters except three traits (leaf rolling, days to first flowering and harvest index). In the present study, the dominance gene effects and dominance x dominance genetic effects were predominant for grain yield and major yield contributing characters joined with duplicate type of epistasis. For enhancement of these characters, selection will be postponed to later on generations or bi-parental mating of breeding method may be followed. An additive gene effect was also significantly positive for all the characters under study. In addition, additive x additive genetic effects also significant and positive for most of the characters. In the present study revealed that, complementary gene effect was observed in drought related trait leaf rolling in all three crosses, number of grains per panicle and spikelet fertility in one cross (PMK 4 x ADT 45). Complementary epistasis was expressed in the cross Norungan x ASD 16 for harvest index. In this situation, additive gene effects were predominant. For improvement of these traits, simple selection procedure and pedigree methods of breeding to be followed.