G. ShanthakumarNaveen Kumar K. L.2017-03-062017-03-06http://krishikosh.egranth.ac.in/handle/1/5810004165A study was conducted to assess the combining ability, nature of gene action and extent of heterosis in respect to grain yield and its component traits, involving 91 hybrids (developed through L x T design using thirty inbreds, three testers) and nine commercial checks in maize during summer and kharif 2013 at MARS, University of Agricultural Sciences, Dharwad. The analysis of variance indicated significant amount of variability among genotypes for 14 quantitative characters studied. The computed variance ratios (GCA: SCA variance) revealed the predominance of non-additive gene action in the inheritance of all the traits. The study on the combining ability revealed that the lines DMIL103, DMIL152, DMIL699, DMIL765 and DMIL767 among the parental lines and DMIL011 and DMIL031 among the testers were identified as the best general combiner for grain yield than the rest in both the season. The study on standard heterosis revealed that 3 hybrids viz., DMIL765 x DMIL031 (13.95%), DMIL318 x DMIL011 (13.08%), DMIL699 x DMIL031 (1.69%) in summer and whereas in kharif DMIL639 x DMIL011 (29.41%), DMIL703 x DMIL031 (25.11%) DMIL688 x DMIL011 (24.53%) exhibited significant positive heterosis over best commercial check Super 900M and also exhibited significant sca effect for grain yield and its components, obtained from the parents with high x high and high x low gca effects. It is suggested to evaluate the identified hybrids in large scale trail to confirm their superiority. The hybrids, DMIL218 x DMIL021 were top cross showed the significant heterosis as well as sca effects for SPAD value (-1.96) and canopy temperature (15.58%). Most of these were obtained from the parents with high x high gca effects. So these crosses can be utilized for exploiting hybrid vigor.ennullThesis