Evaluation of heritability and genetic parameters of grain yield and important agronomic traits in maize (Zea mays L.) lines using generations mean analysis method

Enough information about genetic parameters, including heritability and gene action, is the first step in breeding of a trait. Among different methods, generation mean analysis, with lower estimation error, is one of the best methods for estimation of genetic parameters. The present experiment was carried out to estimate heritability, number of genes and gene action for some agro-morphological traits in maize. The seeds of the generations of P1, P2, F1, F2, BC1 and BC2 were prepared during two successive years and were evaluated based on randomized complete block desine in Golestan Agricultural and Natural Resources Research and Education Center, Iran during 2015. Results of weighted ANOVA showed significant differences between the generations for all traits, therefore, generation mean analysis was performed. While, additive effect and relative dominance controlled ear length, number of row.ear-1, cob diameter and cob percentage, the additive, dominance and epistatic effects controlled the other traits simultaneously. Difference between dominance and additive components and the average of gene dominance was greater than unity which indicated the role of non-additive and the importance of heterosis effects in expression of these traits. The maximum heterosis and heterobeltiosis belonged to ear biomass and grain yield respectively. The broad and narrow sense heritability of the traits was ranged from 62.41 to 90.06 and 3.46 to 60.40, respectively. The average number of genes was ranged from 0.03 to 4.74 for different traits. In general, unlike grain yield, selection in early generations for yield-related traits with high narrow sense heritability such as ear length, cob diameter, 250-grain weight and number of grain.row-1, may improve grain yield in advanced generations. In addition, due to the high narrow sense heritability for cob percent (60.4%), selection in early generations for reduction in percentage of cob, with no significant increase the overall weight of the ear, may increase the ear harvest index and improving grain yield of maize.