Combining ability effects and heterotic grouping in newly developed early maturing yellow maize (Zea mays L.) inbreds under sub-tropical conditions
A field experiment was conducted at Experimental Farm, Shivalik Agricultural Research and Extension Centre, Kangra representing subtropical conditions of north western Himalayasecology during Kharif 2017 to estimate combining ability of newly developed early maturing yellow maize inbred lines. Twenty two crosses were generated by crossing 11 new developed yellow maize inbreds with 2 diverse testers using Line x Tester mating design. The experiment was conducted using randomized block design with two replications. The mean square due to genotypes, parents and parents v/s crosses were significant for all the traits, except for days to 50 per cent silking due to genotypes, kernel rows, days to 50 per cent tasseling and days to 50 per cent silking due to parents. This revealed presence of appreciable amount of genetic variability in the experimental material of the present investigation. The ratio of σ2gca / σ2sca for all the studied traits indicated the preponderance of non-additive gene effects in the inheritance of these traits. Among female inbred lines, L9 had significant GCA effects for grain yield per plant (21.64) and yield component traits like shelling percentage (3.24) , ear length(2.37), ear diameter(1.07), number of kernels/row(3.84) and 1000- kerenel weight (8.68) , indicated that best general combiner for these traits, while in male parent T2 was the best general combiner for yield contributing traits viz., ear length (0.47), ear diamter (0.19), number of kernel rows per ear (0.59), number of kernels/row (1.02) and 1000-kernel weight (10.05). On the basis of mean grain yield and SCA effects, three test crosses, viz., L9xT2, L5xT1, and L1xT1 were identified most promising and may be further tested at multi environments for use as single cross hybrids. L9xT2 manifested highest mean grain yield (102.17g/plant) and significant positive specific combining ability effect (15.93). Based on the SCA effect for grain yield, the newly developed inbreds were classified into two heterotic groups. The lines L1, L2, L4, L5 and L6 belonged to tester group CM-212, while L3, L9, and L11 belonged to heterotic group of HKI-1105. Inbred lines assigned into two opposite heterotic groups could be used as parents to develop hybrids and inbred lines with same heterotic group with positive GCA may be used for synthetic variety development.
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