Estimation of Gene Action for Grain Yield and Yield-related Traits in Grain Maize (Zea mays L.) under Moisture Stress Conditions

To determine the type of genes action and estimate genetic parameters under moisture stress condition, two inbred lines of S0200237 (P1) and ILYH0231 (P2), sensitive and resistant to moisture stress, respectively, were crossed in 2013. Six generations P1, P2, F1, F2, BC1 and BC2 were planted in a randomized complete block design in 2015 and generation mean analysis was performed. Significant and positive heterosis was observed for ear biomass/ plant and ear-grain yield/plant. The joint scale test and the average of gene dominance confirmed the inadequacy of the additive-dominance model for most traits, indicating the importance of epistatic and over-dominant effect in genetic control of the traits. The results showed that row number/ear, ear diameter, cob diameter and grain depth were controlled by additive effect. The broad and narrow sense heritability of the ranged varied from 68.9 to 88.6 and 13 to 50.40, respectively. The average of genes number controlling the traits varied from 1-7 genes for grain yield. The maximum positive heterosis was observed for ear biomass and grain yield per plant. Generally, selection in early generations for grain yield-related traits with high narrow sense heritability, including the number of rows per ear, will improve grain yield in advanced generations. In addition, selection in early generations to reduce cob percent, to some extent, does not result in a significant reduction in total ear weight, and will result in an increase in harvest index, thus improves grain yield under moisture stress conditions.