Genetic Analysis Of Maturity And Yield Attributes In Subtropical Maize

Knowledge of the genetic parameters like gene action, heritability, genotypic and phenotypic association among traits and heterotic levels helps the plant breeders in developing breeding strategies.Four white grain maize inbred lines from flint group of corn, two with late maturity (100 - 120 days) and two with early maturity (90 - 100 days) were selected for this study.These contrasting inbred lines were crossed to form four crosses.Six generations i.e., P1, P2, F1, F2, BC1, and BC2 were developed for each individual cross and a total of 20 entries were evaluated in triplicate for two consecutive years (2006 and 2007) during summer season (July – October) at experimental farm of Cereal Crops Research Institute (CCRI), Pirsabak, Nowshera, NWFP, Pakistan.The objectives of the study were to elucidate the pattern of inheritance and to determine the relative magnitude of various genetic effects, broad and narrow sense heritability estimates, mid-parents and better parent heterosis, genotypic and phenotypic correlations and to ascertain the best hybrid combination(s) for commercial cultivation in maize growing belt of NWFP.Both dominance gene action and epistatic interaction played major role in governing the inheritance of days to pollen shed, silk, maturity, ear height, grains ear-1 and harvest index, whereas ear diameter, shelling percentage, stover and biological yields were mostly controlled by dominance gene action. Additive and dominance gene actions were seen only for 100-grain weight and grain yield efficiency. Leaf area, leaf area index, plant height, ear weight, ear length, kernel rows ear-1, grains row-1 and grain yield were found to have been controlled by additive, dominance and epistatic gene interactions.High heritability estimates were observed for all the plant traits except kernel rows ear-1 and shelling percentage which were of moderate levels.Significant and positive association was observed among most of the grain yield associated traits and between physiological and grain yield related traits.Ear weight, grains ear-1, grain yield, grain yield efficiency, stover yield and biological yield exhibited high heterotic levels while most of the other traits showed moderate levels of heterosis except days to pollen shed, silk and maturity, ear diameter, kernel rows, shelling and harvest index which indicated low levels of both mid-parents and better parent heterosis. Based on the present results it would be worthwhile to utilize the parental lines of the crosses that exhibited additive and dominance gene actions, coupled with high narrow sense heritability estimates and having strong relationship along with high heterotic levels for most of the physiological as well as grain yield related traits in the improvement of maize breeding germplasm of subtropical nature.Moreover, these lines could be successfully used for the development of superior maize hybrids.The resulting hybrid particularly Pop.9804 x FRW-4 was outstanding for yield attributes and can, therefore, be recommended for commercial cultivation in sub-tropical climates after testing on multiple locations to confirm its yield superiority.