Study of genetic diversity and grouping pattern bread wheat genotypes under water deficit- stress

Crop yield products reduction due to abiotic stress is estimated at 51 to 82%. Most plants are exposed to environmental stresses, and water deficit is one of the most important non-abiotic stresses in limiting and producing crops around the world, especially in arid and semi-arid regions. Plants have developed various strategies to cope with water deficit stress, including morpho-physiological and biochemical.Wheat is one of the most important crops in the world, which in 2020 had the highest area under cultivation at the rate of 221.33 million hectares (with a total production of 766.03 million tons) worldwide. In the same year in Iran, the area under wheat cultivation was 6.70 million hectares and its production was 16.75 million tons.

The research was performed in research farm of Rainfed Agricultural Research Station Gachsaran, Iran, over 2020-2021 cropping years. In this study, 100 lines obtained from the landrace bread wheat of different origins from several continents and several countries were studied. The experiment was performed in a simple lattice design 10×10 with two replications and separately in two environmental conditions of stress and non-stress. The operation planting is done in January after conventional tillage implementation of the area by hand. The source of moisture supply for both rain fed (water deficit stress) and irrigation (no stress) test conditions was rainfall and sprinkler irrigation before the phonological stage of flowering (pollination (Zadocs scale 61)). Irrigation interruption was applied at the beginning of flowering in a stress environment (water deficit stress conditions) which continued until harvest, but the environment without stress in two times when wheat plants to early reproductive stage, flowering stages, and the beginning of grain filling (Grain paste stage (Zadocs scale 61-83)) Irrigation was performed. In this study, 16 morphological traits and grain yield were measured under both stress and non-stress conditions, including flag leaf length and width (cm), flag leaf pod length (cm), and flag leaf area (cm2), number of nodes and leaves per stem, internodes number, peduncle length (cm), plant height (cm), tiller number, fertile and infertile tillers of number, length of awn (cm), spike length (cm) and spike yield (g).

The results of the analysis of variance showed high and significant variability in both non-stress and deficit water stress. TRI 3492 was the most tolerant of geographical origin in Nepal and TRI 4549 had the lowest STI relative to deficit water stress of geographical origin in China. The highest and lowest heritability in stress conditions were related to plant height (98.02%) and the number of intermediate nodes (25.00%), respectively. The greatest decrease in heritability (66%) due to stress conditions was the leaf sheath length of the flag leaf. Among the traits studied in this study, flag leaf area with 31.41%, flag leaf length with 25.25% and grain yield with 23.53% had the highest percentage of stress reduction. The results of cluster analysis of the studied genotypes in both environmental conditions are in six separate and different groups so that the greatest difference in genetic distance and grain yield in both environmental conditions was observed between the first and sixth clusters.

Using the genotypes of first cluster (TRI 403, TRI 4013, TRI 3981, TRI 10340, TRI 5262, TRI 4549, TRI 2513, TRI 2656, TRI 3477, TRI 3242, TRI 3526, TRI 3513, TRI 4116 and TRI 4113) with 6TH cluster (TRI 10296, TRI657, TRI755, TRI752, TRI757, TRI 11020, TRI691, TRI 6129 and TRI754) Can be used in crossbreeding programs as well as genetic studies (such as recombinant populations and association mapping) and to increase the rate of heterosis used in water-deficit stress conditions.