Genetic Diversity in Wild and Weedy Aegilops, Amblyopyrum, and Secale Species—A Preliminary Survey

Abstract

The wild and weedy relatives of bread wheat, Triticum aestivum L., are suggested as potential sources of useful alleles for bread wheat improvement. For example, the genus Aegilops L. has contributed two of the three bread wheat genomes. In this study we measured the nature and extent of allozyme variation for 10 isozymes in three diploid and eight polyploid Aegilops, one Amblyopyrum (Jaub. & Spach), and one feral Secale L. species collected from 15 populations in their centers of origin in Syria, Lebanon, Turkey, and California. The predominantly autogamous Aegilops species were, to a large extent, homozygous and homogeneous. The presence of heterozygous genotypes in Aegilops tauschii Coss. (H0 = 0.0033 ± 0.01) and Ae. crassa Boiss (H0 = 0.0048 ± 0.08) indicated the possibility of limited facultative outcrossing in these Aegilops species. The obligate outcrossers, Amblyopyrum muticum (Boiss.) Eig (He = 0.09 ± 0.16) and Secale cereale L. (He = 0.09 − 0.13), showed less than expected genetic variation. The extent and nature of genetic variation were identical between the introduced Californian Ae. cylindrica Host and that which occurs in the Fertile Crescent (He = 0.00); however, in Ae. triuncialis L., the introduced Californian population had a higher genetic diversity estimate (He = 0.06 ± 0.12) than the population from the Fertile Crescent (He = 0.00). The average genetic distance between the polyploid Aegilops species was greater (D = 0.64 ± 0.28) than that observed between the diploid Aegilops species (D = 0.18 ± 0.10), or between the diploid Aegilops and weedy S. cereale (D = 0.52 ± 0.06). We discuss the implication of these findings for germplasm collection and wheat breeding.