Restriction fragment length polymorphism in wild and cultivated tetraploid wheat

RFLP diversity in the nuclear genome was estimated within and among Israeli populations of wild emmer wheat (Triticum turgidum var. dicoccoides) from a long-term study site at Ammiad (NE Israel), and from several other geographical locations. Using 55 enzyme-probe combinations, high levels of genetic diversity were revealed in wild emmer in general and within the Ammiad site. In spite of high diversity, observed heterozygosity was low and populations consisted of a patchwork of alternate multilocus homozygotes, consistent with the reproductive biology of a predominant self-fertilizing species. Retention of genetic diversity in wild emmer may be promoted by large population sizes, microhabitat diversity, and occasional gene flow through both pollen and seed. Population genetic structure in wild emmer appears to have been influenced by historical founder events as well as selective factors. Multivariate analyses indicated that individuals tend to cluster together according to their population of origin, and that there is little geographical differentiation among populations. Sampling of 12 domesticated land-races and both primitive and modern cultivars of T. turgidum revealed high levels of diversity and a large number of alleles that were not detected in the wild emmer populations. This may reflect a long-term domestication process in which wild, semi-domesticated, and domesticated types grew sympatrically, continuing introgression from wild populations, and perhaps also gene flow from trans-specific sources.