Genetic diversity in wild wheats and goat grass

Abstract 

The genetic structure of 35 populations of wild relatives of cultivated wheats, all collected in Syria and Lebanon, was assessed using ten isozymes. The populations consisted of diploid goat grass, Aegilops speltoides, diploid wild wheats, Triticum monococcum spp. aegilopoides and T. urartu, and tetraploid wild wheat, T. turgidum ssp. dicoccoides. The majority of the populations were polymorphic (P=0–70%) having low within-population mean genetic diversity (H_ep=0.05–0.10) and relatively high within-species genetic diversity (H_es=0.14–0.31). The linkage between loci did not seem to be one of the causes for the observed polymorphism. All four species showed significant inbreeding at both the population (0.31–0.64) and species (0.77–0.96) levels, and the extent of inbreeding did not correlate with mating systems. Despite their apparent common ecological and evolutionary history, between-population or between-species level genetic identity was low (I=0.43–0.86). Among the diploid species, populations of Ae. speltoides clustered distinctly from those overlapping clusters of T. monococcum ssp. aegilopoides and T. urartu. The tetraploid species T. turgidum ssp. dicoccoides had relatively less genetic diversity (H_es=0.14) and was highly homozygous (F=0.96). The results suggest that these wild progenitors of cultivated wheats have undergone extensive local differentiation and inbreeding. We discuss the implications of our results on the management of wild wheat and goat grass populations.