Combining Ability in Maize Under Varying Plant Densities¹

All possible crosses (reciprocals bulked) among 20 varietal populations of maize were evaluated at two plant population levels. Significant differences due to GCA and SCA were observed for all characters in both the trials except for grain yield for SCA in high density experiment. General combining ability effects were not drastically influenced by plant population levels, particularly for the height, the expression of which was predominantly controlled by GCA. The relative magnitude of σ²_g and σ²_s was inconsistent over plant population levels and it seemed that the expression of σ²_s was more susceptible to environments. Low (normal) plant density environment was observed to be more conducive for expression of genetic differences as heritability estimates were low at high plant density. It is stressed that further experimentation particularly with new germplasm will be useful.