Investigation of Genetic Diversity of Bread Wheat Accessions in terms of Agronomic Traits and SSR Molecular Markers

The study of genetic diversity in crops is essential for breeding programs and conservation of heritage resources and is a key step in assessing the adaptation of the population to new environmental conditions and thus the selection of new cultivars. There are various methods for estimating genetic diversity in different plant species, including the use of morphological traits and DNA markers.

For this purpose, in this study, genetic diversity between 25 bread wheat accessions in terms of 23 agronomic traits and 20 SSR molecular markers was investigated. A field experiment was conducted in 2016-2017 in the form of a randomized complete block design with three replications in rainfed and irrigation at the end of the growing season conditions in the research farm and laboratories of the Faculty of Agriculture and Natural Resources of Razi University.

The results of analysis of variance showed that there was a significant difference between the accessions for most of the studied traits. Based on the results of cluster analysis, the accessions were divided into four groups. The results of comparing the mean and cluster analysis showed that accessions 2, 13, 6, 15, 18 and 10 were the best accessions based on agronomic characteristics, which can be suggested for breeding programs, and in contrast to accessions 3, 24, 11, 12 and 16 as the weakest accessions in terms of The studied agronomic traits were identified. In assessing the genetic diversity of the populations using 20 SSR markers, 16 primers with suitable polymorphisms were selected. The percentage of total polymorphism was estimated to be 93.75. XCFD168-2D, XGWM350-7D and XGWM136-1A primers with 100% polymorphism, maximum number of alleles, high amount of polymorphic information content indices, marker index, effective multiplex ratio index and resolving index due to the high proliferation of bands and the production of high polymorphic bands, they were introduced as the most suitable primers for wheat in subsequent studies. Molecular analysis of variance showed that the degree of diversity within the groups was greater than the diversity between the groups. The results of cluster analysis by UPGMA method based on Jaccard similarity coefficient led to the classification of 25 bread wheat accessions in four different groups, which showed high agreement with the results of analysis to the main coordinates, and finally accessions 1, 3 and 25 had the greatest genetic distance with accessions 13 , 7 and pioneer cultivars, so it is possible to suggest the selection of parents from these two groups for breeding programs.

Evaluation of agronomic characteristics showed that accessions 2, 13, 6, 15, 18 and 10 are superior accessions, among which, oxides of external and internal origin were observed. In evaluating the genetic diversity of the accessions, the primers XCFD168-2D, XGWM350-7D and XGWM136-1A were identified as the most suitable primers for wheat in subsequent studies. Markers with high polymorphism as well as markers and accessions with unique bands in the banding pattern are also of great value for breeding programs, for example, identifying genes useful for resistance to various biological and abiotic stresses in wheat and promoting its various cultivars.