Abstract
Despite the global value of barley, compared to its wild progenitor, genetic variation in this crop has been drastically reduced due to the process of domestication, selection and improvement. In the medium term, this will negatively impact both the vulnerability and yield stability of barley against biotic and abiotic stresses under climate change. Returning to the crop wild relatives (CWR) as sources of new and beneficial alleles is a clear option for enhancing the resilience of diversity and adaptation to climate change. Southeastern Anatolia constitutes an important part of the natural distribution of wild barley in the Fertile Crescent where important crops were initially domesticated. In this study, we investigated genetic diversity in a comprehensive collection of 281 geo-referenced wild barley individuals from 92 collection sites with sample sizes ranging from 1 to 9 individuals per site, collected from southeastern Anatolia and 131 domesticated genotypes from 49 different countries using 40 EST-SSR markers. A total of 375 alleles were detected across entire collection, of which 283 were carried by domesticated genotypes and 316 alleles were present in the wild gene pool. The number of unique alleles in the wild and in the domesticated gene pool was 92 and 59, respectively. The population structure at K = 3 suggested two groups of wild barley namely G1-W consisting wild barley genotypes from the western part and G1-E comprising those mostly from the eastern part of the study area, with a sharp separation from the domesticated gene pool. The geographic and climatic factors jointly showed significant effects on the distribution of wild barley. Using a Latent Factor Mixed Model, we identified four candidate loci potentially involved in adaptation of wild barley to three environmental factors: temperature seasonality, mean temperature of driest quarter, and precipitation of coldest quarter. These loci are probably the targets of genomic regions, with potential roles against abiotic stresses.
Highlights
Archeological evidence suggests that barley (Hordeum vulgare L. ssp. vulgare) was domesticated more than 10,000 years ago in the Fertile Crescent [1]
The highest polymorphism information content (PIC) and genetic diversity (GD) were observed for marker GBM1015 (0.859 and 0.871 respectively) and the lowest values were observed for GBM1404 (0.103 and 0.105 respectively)
The genetic diversity analysis revealed a high number of alleles (375 in total) across the entire collection of wild and domesticated barley
Summary
Archeological evidence suggests that barley (Hordeum vulgare L. ssp. vulgare) was domesticated more than 10,000 years ago in the Fertile Crescent [1]. The core distribution area of wild barley is the Fertile Crescent, but it naturally occurs from western North Africa to the Himalayas [2] Compared to their wild relatives, the domestication process of crop plants usually leads to genetic bottlenecks causing considerable reduction of genetic variation, which is a major concern for plant breeders today. One approach is to identify useful alleles within crop wild relatives and landrace genepools [4] To achieve this goal, the analysis of genetic variation of crop plants and their wild progenitors is important, considering materials from the center of domestication and/or the center of highest diversity [5]. Ecological and geographical data have been considered as important factors to improve sampling strategies and managing genetic diversity [8,9]
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