Heterosis and Combining Ability Analysis for Grain Yield and Related Traits in Maize (Zea mays L.).

The present investigation on maize (Zea mays L.) was carried out to generate information on combining ability (general and specific) and its interaction with environment gene action and heterosis for yield and 16 morpho-agronomic traits. The experimental material comprised of a diallel set involving 12 diverse inbred lines excluding reciprocals and two standard checks (W3 x W5 and C15). The experimental material was evaluated in randomised complete block design having two replications over two locations namely High Altitude Rice Research Sub-Station, Larnoo (E1) and Experimental Farm, Division of Plant Breeding and Genetics, Shalimar (E2) of SKUAST-K during Kharif, 2007.The data were recorded on days to 50% anthesis, days to 50% silking, days to 75% husk browning, plant height (cm), ear height (cm), ear leaf length (cm), ear leaf breadth (cm), profilicacy index (%), ear length (cm), ear girth (cm), kernel row number per ear, kernels per row, grain depth (cm), shelling percentage, 100-seed weight (g), grain yield per plant(g) and protein content (%). The mean values were used for statistical analysis and estimation of genetic parameters following diallel analysis (Griffing, 1956 and Hayman, 1954). The combining ability analysis over environments was carried out as per Singh (1973a, 1979). Analysis of variance revealed significant differences among the lines and crosses. The variance due to GCA and SCA was significant for all the traits studied which showed that both were important in the inheritance of the traits. Significant interaction between combining ability effects and environments were observed for most of traits. The estimate of dominance deviations was higher in magnitude than the corresponding additive genetic variance for all the traits in individual environments as well as pooled over environments which demonstrated the feasibility of production of hybrids. None of the parents was found to be good general combiner simultaneously for all characters. However, PMI-67was identified as good general combiner for most of traits viz, early maturity traits, grain yield per plant, 100-grain weight, ear girth, grain depth, ear leaf length protein content and ear leaf breadth whereas PMI-69 was the best general combiner for early maturity traits, reduced plant height, protein content and low ear placement. PMI-298 was the most desirable general combiner for grain yield per plant. The most promising crosses that revealed highly significant and positive SCA effect for grain yield were PMI-67 x PMI-69, PMI-48 x PMI-224, PMI-360 x PMI-401, PMI-118 x PMI-360 and PMI-03 x PMI-64.These crosses were mostly the result of high x low or low x low or low x average general combiners. On the basis of per se performance five top ranking cross combinations for grain yield included PMI-117 x PMI-298, PMI-67 x PMI-69, PMI-224 x PMI-298, PMI-118 x PMI-298 and PMI-64 x PMI-67. High per se performance in general, was strongly associated with specific combining ability effects. Protein content among crosses was lowest for PMI-03 x PMI-64 (7.70%) and highest for PMI-224 x PMI-298 (12.30%). High SCA effects in desired direction was usually found strongly associated with high protein content. The component analysis indicated preponderance of non-additive gene effects in inheritance of all traits studied. Average degree of dominance was in over dominance range for all characters. The gene distribution was observed to be asymmetrical for all traits with positive and negative effects in parents for most of the characters. The value of KD/KR indicated presence of excess of dominant genes for all trait except 100-grain weight, ear girth and prolificacy index. Low to moderate estimates of heritability (narrow sense) were recorded. Significant and desirable heterosis was observed for most of the traits. The maximum heterosis for grain yield per plant was registered by PMI-117 x PMI-298 followed by PMI-67 x PMI-298, PMI-224 x PMI-298, PMI-118 x PMI-298 and PMI-64 x PMI-67. Higher magnitude of Hetrobeltiosis and standard heterosis in the favourable direction for grain yield and component traits suggested the possibility of yield enhancement in maize through the exploitation of heterosis breeding