Combining ability analysis for drought tolerance in rice (O. sativa L.) under reproductive stage

An investigation in rice (Oryza sativa L.) was carried out to study the nature of gene action governing drought tolerant and yield contributing traits under reproductive stage drought stress. Nine genotypes from varied sources including land races, pre-release cultures, drought tolerant varieties and tropical japonica types were crosses in diallel analysis. The results indicated that predominant role of dominance gene action for all the drought tolerant traits except leaf drying and all the yield contributing traits except days to 50% flowering and plant height. Additive gene action was predominant for plant height, while both additive and dominance gene actions were equal in magnitude for days to 50% flowering and leaf drying. The parents viz., CT 9993, Moroberekan, Nootripathu, Kallurundaikar, PMK 2 and Norungan are found to be promising in producing superior segregants for physiological and morphological mechanisms of drought tolerance along with grain yield. The hybrids Nootripathu / Moroberekan, Nootripathu / CT 9993, MDU 5 / Moroberekan, CPMB ACM 04001 / Moroberekan, CPMB ACM 04001 / CT 9993 and PMK 2 / Kallurundaikar could be recommended for recombination breeding to get useful segregants for yield and drought tolerance. Based on per se, sca effects and standard heterosis, the hybrids MDU 5 / CT 9993, Nootripathu / Moroberekan, Kallurundaikar / Moroberekan, Kallurundaikar / CT 9993, PMK 2 / Moroberekan and Norungan / Nootripathu are ideal for heterosis breeding