Evaluation of genetic diversity of spring barley genotypes with respect to some phenological and morphological traits

Barley (Hordeum vulgare) is the fourth most important crop in the world. It is commonly used for human food, malt, and animal feed. Through the study of pedigrees, morphological and biological traits, and molecular markers, it is possible to estimate the genetic diversity of crops, which plays an essential role in promoting breeding programs and preserving genetic resources. This study aims to identify superior barley genotypes in terms of phenological and morphological traits, group them using cluster analysis, and reduce the measured traits using principal component analysis. To evaluate the genetic diversity of spring barley genotypes based on phenological and morphological traits, an experiment was conducted at Divandareh Dryland Agricultural Research Station using a randomized complete block design with 27 genotypes in four replications. In this investigation, plant height, tillering date, shooting date, flag leaf width, flag leaf length, awn length, spike length, internode length, diameter at node location, internode diameter, flowering date, dough stage, milk stage, rootlet weight, grain yield per plant, biomass per plant, total biomass, 1000 grains weight, harvest index, number of fertile stems, number of florets per spike, number of grains per spike, number of leaves at spike emergence, germination date, maturity date, number of grains per plant, spike emergence date and total grain yield were evaluated. Analysis of variance was performed, and the method of least significant differences was used to compare the means (LSD). Using Pearson's correlation coefficient, the relationship between the studied traits was determined. Principal component analysis was utilized for data reduction. Using cluster analysis, the studied genotypes were grouped. MSTATC and SPSS softwares were utilized for data analysis. Except for flowering date, differences between genotypes were significant for the majority of traits, indicating a high level of diversity among spring barley genotypes. Greater heritability was observed for total grain yield, number of fertile shoots, main spike length, harvest index, and flag leaf length than for other traits. These traits can be used to segregate generations for indirect grain yield selection due to their high heritability. Path analysis (by stepwise regression) revealed that number of grains per plant and 1000-grain weight had a direct and significant effect on total grain yield, whereas the direct effect of awn weight on grain yield was less than that of number of grains per plant and 1000-grain weight. Therefore, grain number per plant and 1000-grain weight were the most influential factors in spring barley grain yield. Based on the evaluated traits, the cluster analysis divided the studied genotypes into three groups. The genotype 1 was found in the first cluster, the genotypes 26, 25, 27, 22, 14, 13, and the remaining genotypes were found in the third cluster. The first three principal components in principal component analysis explained 52.88 % of the total variance. The respective values for the second and third components were 17.23% and 9.15%. The traits of booting date (0.884), number of grains per spike (0.855), flowering date (0.776), and flag leaf width (0.883) had positive coefficients and high values in the first component. In the second component, plant height (0.885), shooting date (0.880), and flag leaf length (0.873) all had large positive coefficients, whereas 1000 -grain weight (-0.387) and plant weight (-0.377) had large negative coefficients. The number of leaves can be proposed as the third component. Cluster emergence date (0.586), milk stage (0.739), and number of grains per plant (0.570) had high coefficients in the third component. The third component is maturity-related characteristics. According to the means, the third cluster of genotypes can be utilized in grain yield breeding programs. Based on the results, the first component shall be designated as the grain yield and total biomass component. This component can be used for spring barley genotype selection.