Genome-wide association mapping of Pyrenophora teres f. maculata and Pyrenophora teres f. teres resistance loci utilizing natural Turkish wild and landrace barley populations.

Unimproved landraces and wild relatives of crops are sources of genetic diversity that were lost post domestication in modern breeding programs. To tap into this rich resource, genome-wide association studies in large plant genomes have enabled the rapid genetic characterization of desired traits from natural landrace and wild populations. Wild barley (Hordeum spontaneum), the progenitor of domesticated barley (Hordeum vulgare), is dispersed across Asia and North Africa, and has co-evolved with the ascomycetous fungal pathogens Pyrenophora teres f. teres and P. teres f. maculata, the causal agents of the diseases net form of net blotch and spot form of net blotch, respectively. Thus, these wild and local adapted barley landraces from the region of origin of both the host and pathogen represent a diverse gene pool to identify new sources of resistance, due to millions of years of co-evolution. The barley-P. teres pathosystem is governed by complex genetic interactions with dominant, recessive, and incomplete resistances and susceptibilities, with many isolate-specific interactions. Here, we provide the first genome-wide association study of wild and landrace barley from the Fertile Crescent for resistance to both forms of P. teres. A total of 14 loci, four against P. teres f. maculata and 10 against P. teres f. teres, were identified in both wild and landrace populations, showing that both are genetic reservoirs for novel sources of resistance. We also highlight the importance of using multiple algorithms to both identify and validate additional loci.