Genetic investigations of yield and yield components in an exotic gene pool of maize(Zea mays L.)

Pool-40 an exotic germplasm of maize (Zea mays L.) introduced form CIMMYT was used as the base population to study the nature and magnitude of genetic variances, genotype x environment interactions, level of dominance and other related parameters like heritability (in narrow sense) and grains expected to be realized through full-sib family selection. Bi-parental progenies generated through Design-1 and II of Comstock and Robinson (1948, 1952) were evaluated under two random environments in an incompletely Randomized Block Design. Observations were recorded on grain yield per plant, ear length, ear diameter , kernel rows per ear, 100-kernel weight and other traits like days to tassel/silk, plant height and ear height. Comparison of the relative magnitude of the additive genetic variance and variance due to dominance deviation estimates revealed that additive genetic variance was more important than the variance due to dominance deviations for all the traits studied under the two NC designs except for grain yield per plant which showed equal importance of both these genetic components of variance in the inheritance of this trait. Negative estimates of dominance variance were confined to Design-1 for days to tassel, days to silk and ear height. G x E interaction studies revealed that additive genetic variance was not, in general greatly affected by the environment. On the contrary, the component of variance due to dominance deviations showed greater interaction with the environment. This indicated that additive genetic variance was more stable than the other over the environments. Estimates had higher values in Design-II than in Design-I. Presence of substantial genetic variability for grain yield in the reference population revealed that genetic gain (through full-sib family selection) would be around 6.0 to 6.5 per cent per cycle. Comparison of the various estimates obtained through the two NC designs revealed that the estimates for Design-II are more realistic and therefore, reliable. These studies indicated that there is ample scope for improvement of this gene pool with reference to grain yield and other related traits through some cyclic selection scheme. Partial to complete lines of dominance exhibited by the traits also offers opportunities for isolating superior inbred lines for development of hybrids. Besides, the introgression of some of the traits from this gene pool can broaden the genetic base of the local germplasm in combating biotic and abiotic stresses