Genetic Analysis of Grain Yield and Related Traits in Maize (Zea mays L.) Using Graphical Diallel Analysis

The first step in breeding programs is accurate identification and sufficient knowledge of genetic parameters, including the type of gene action and the heritability of the studied trait. Development of high yielding lines and the identification of heterotic groups are the most important objectives of corn breeders. Also, determining the inbred lines of parents that create suitable hybrids is very valuable and can reduce the duration of the hybrid production program in corn. Graphic diallele analysis is one of the biometric methods of genetic analysis of quantitative and multigenic traits, the results of which can be very useful for improving traits within and between populations as well as producing hybrid varieties. The objective of this experiment was to investigate the genetic control of grain yield and related traits in maize inbred lines. The results of this study can be useful in selecting the most appropriate breeding method for the studied traits and producing high yielding maize hybrids in Zanjan region, Iran.

To estimate the type of gene action, the number of genes, heritability and other genetic parameters controlling grain yield and its related traits in maize inbred lines, a 5×5 diallel crosses design was used. The parents and 20 hybrids derived from their crosses were evaluated in a randomized complete block design with three replications in the research field of Zanjan University, Zanjan province, Iran, in 2019. The studied traits were including plant height, ear length, number of grain rows in ear, number of grains per row, 300-grain weight, and grain yield. The genetic analysis of the data was done according to Hayman (1954) graphical approach.

Estimating the genetic parameters showed both additive and non-additive gene effects in controlling the studied traits in this research. The results of graphical analysis also indicated the existence of over-dominance gene effects in controlling grain yield and its related traits. The alleles increasing the studied traits were of dominant type. Broad-sense heritability varied from 54% for 300-grain weight to 89% for ear length, and narrow-sense heritability ranged from 29% for 300-grain weight to 41% for number of grain rows per ear. Although high general heritability was estimated for most of the studied traits, which indicates the greater role of genetic factors and the relatively less influence of environmental factors in controlling the diversity of these traits, the existence of over-dominance effect of genes and low narrow-sense heritability indicates that the selection of these traits in the early generations will not be successful. Therefore, the breeding methods based on hybridization and selection in advanced generations can be useful in improving and breeding the grain yield and its related traits in the studied maize inbred lines. Also, the use of EP80 inbred line which had the most number of dominant genes for controlling yield and its components may have promising results in improving these traits in breeding programs.

In total, the results of the current study regarding the type of gene action controlling grain yield and its components in the studied maize inbred lines showed the important role of the over-dominance effects of genes. Therefore, the most appropriate strategy for exploiting these genes and improving the population is to obtain hybrid varieties that provide the possibility of exploiting heterosis in the investigated parents. is to use the heterosis phenomenon and produce hybrid varieties.