Investigation of Genetic Diversity and Grouping of Barley Genotypes Based on Indices Related to Grain Yield under Rain-fed and Supplemental Irrigation Conditions

In a Mediterranean-type climate, water stress, which often occurs at the end of the season, is the main factor limiting cereal yield. This study aimed to investigate the genetic diversity, heritability, and genetic Advance of some indices related to grain yield in barley under rain-fed conditions.

In this study, 108 lines and varieties of barley were evaluated as alpha lattice designs with two replications in nine blocks in each replication and twelve plots in each block under rain-fed and supplemental irrigation (irrigation, immediately after planting and in the stage of grain filling) conditions during 2019-2020 crop season at Maragheh Dryland Agricultural Research Station. The evaluated traits included grain yield, days to heading, days to physiological maturity, grain filling rate, thousand-grain weight, harvest index, spike harvest index, spike fertility index, spike fertility index at maturity, and spike partitioning index.

The analysis of variance showed highly significant differences among the genotypes for all the studied Characters. This implies that there is genetic diversity for all traits. The phenotypic coefficient of variation (PCV) was generally higher than the genotypic coefficient of variation (GCV) for all characters. The difference between PCV and GCV was large in spike fertility index at maturity, spike fertility index, and grain yield indicating the influence of environmental factors in the expression of these traits. Moderate to high heritability associated with a high genetic advance was observed for thousand-grain weight, grain filling rate, and spike fertility index indicating a predominance of additive gene action for these characters. This shows that selection is effective in improving these traits. Based on the cluster analysis by the ward's method and using the Euclidean distance, the examined genotypes were divided into four main groups under both rain-fed and supplemental irrigation conditions. Under rain-fed conditions, genotypes of the first group regarding traits, grain yield, seed filling speed, thousand seed weight, harvest index, spike fertility index, and spike partitioning index, and under supplemented Irrigation conditions, genotypes of the second group regarding traits, grain yield, seed filling speed, thousand seed weight, harvest index, spike harvest index, spike fertility index, and spike fertility index at maturity was in a better position.

Based on the obtained results, it is expected that the grain yield can be indirectly improved by selection for the traits of thousand-grain weight, grain filling rate, and spike fertility index. According to the cluster analysis results, under conditions rain-fed, the first group's genotypes and supplemented Irrigation conditions, the second group's genotypes can be considered in plant breeding programs or variety introduction.