Studies on combining ability and heterosis for yield and drought tolerance traits in rice (Oryza sativa L.)

A research study was conducted involving four high yielding rice varieties viz., CO 51, MDU 6, ADT (R) 45 and ASD 16 as lines and fve drought tolerant genotypes viz., CR Dhan 201, CR Dhan 203, DRR DHAN 42, Apo and GP 239 as testers to understand the nature of gene action, combining ability of parents and hybrids, the extent of heterosis for drought tolerance and yield traits. The ratio of GCA and SCA were less than unity revealed the predominance of dominance gene action for all the drought tolerant and yield traits. Based on both per se performance and gca, the lines viz., MDU 6, ADT (R) 45 and the tester viz., DRR DHAN 42 were identifed as the best general combiners for yield and drought related traits. Hence, these parental genotypes could be used in developing cross combinations to produce desirable segregants with various mechanisms of drought tolerance and grain yield. Among the 20 hybrids, CO 51 x CR Dhan 203 and MDU 6 x CR Dhan 201 were good specifc combiners, which had signifcant sca effects for many yield and drought tolerant traits. The crosses MDU 6 x DRR DHAN 42 and ADT (R) 45 x DRR DHAN 42 exhibited signifcantly positive heterosis for panicle length, productive tillers, chlorophyll stability index, relative water content, flled grains per panicle, grain yield, root length, dry root weight, root volume, root thickness and root/shoot ratio. Combining per se performance, sca and standard heterosis, the hybrids MDU 6 × DRR DHAN 42, ADT (R) 45 ×DRR DHAN 42, ASD 16 × DRR DHAN 42 and MDU 6 × CR Dhan 201 were identifed as superior hybrids since they possessed good performance for many drought tolerant traits.