Divergent diversity patterns of NBS and LRR domains of resistance gene analogs in wild emmer wheat populations

Disease resistance (R) genes are intriguing in their evolution and diversity patterns because of their constant interactions with evolving pathogens. In this study, we demonstrate the use of resistance gene analog (RGA) markers to estimate genetic diversity among 13 populations (118 genotypes) of Triticum dicoccoides collected along a natural aridity gradient in Israel. The diversity patterns of 204 markers derived from two R-gene domains, nucleotide binding site (NBS) and leucine-rich repeat (LRR), were compared and contrasted. Diversity patterns of NBS domain markers differed significantly from those of the LRR domain. NBS markers showed higher between-population diversity (F _st = 0.58), while LRR markers showed higher within-population diversity (F_st = 0.35). Gene diversity (H_e) values were twofold higher in the LRR domain than in the NBS domain (0.144 vs. 0.067). LRR H_e values were correlated with precipitation in the spring (r = 0.8, p = 0.01), while NBS H_e values showed no correlation with any ecogeographical variable. The evolutionary and applicative inferences of these findings are discussed. The current study demonstrates that RGA profiling is an excellent tool for studying diversity of R genes in natural plant populations.