Estimation of combining ability and heterosis for drought tolerance in different locations in rice (Oryza sativa L.)

Diallel analysis was carried out in three different environments namely, managed stress, rainfed and dry conditions to study the combining ability and heterosis for 13 yield and drought tolerant traits. Evaluation of parents based on per se and gca effects, the parents Nootripathu, Mattaikar, Vellaichithiraikar, PMK 3 and NPT 107 were identified as the best genotypes for improvement of yield combined with drought tolerance . The hybrids viz., NPT 107 / MDU 5 for rainfed and dry condition and NPT 107 / Nootripathu for managed stress condition were observed to have parallelism between desirable mean, sca effects and standard heterosis for most of the drought tolerant traits besides grain yield and hence these hybrids were recommended for commercial exploitation of heterosis. The hybrids obtained by crossing the good general combiners viz., For the crosses of good general combiners viz., PMK 3 / Vellaichithiraikar, PMK 3 / Nootripathu and Vellaichithiraikar / Nootripathu, can be recommended for the development of high yielding drought tolerant varieties through pedigree method of breeding . For the hybrids of either with one good and one poor combiners viz., PMK 3 / MDU 5, PMK 3 / ASD 16, PMK 3 / Mattaikar, PMK 3 / Norungan, NPT 107 / Nootripathu and ASD 16 / Vellaichithiraikar, the biparental or reciprocal recurrent selection method may be followed to obtain desirable early segregants and for the cross combinations of both poor combiners viz., NPT 107 / MDU 5, MDU 5 / Mattaikar and MDU 5 / Norungan, since they involved non-additive gene action, cyclic method of breeding involving selection of desired recombinants and their inter se crossing would be more desirable.