Geographical variation of the alleles at the two prolamin loci, Pro1 and Pro2, in foxtail millet, Setaria italica (L.) P. Beauv.

Allelic variation at the two prolamin loci (Pro1 and Pro2) and its geographical distribution in 560 local cultivars of foxtail millet (Setaria italica) mainly from Eurasia were studied using SDS-polyacrylamide gel electrophoresis (SDS-PAGE). Genetic analysis of a newly detected polymorphic band, band 6, indicated that it is controlled by an allele at the Pro2 locus, which was designated as Pro2f. Two alleles (Pro1a and Pro1null) at the Pro1 locus and six alleles (Pro2a, Pro2b, Pro2c, Pro2d, Pro2e and Pro2f) at the Pro2 locus were detected among the cultivars examined. Although the frequency of the Pro1a allele varied from 0% in the Nansei islands of Japan and Africa to 66% in Afghanistan, no apparent trend was observed in geographical distribution. In contrast, two common alleles at the Pro2 locus, Pro2b and Pro2f, had clear differential geographical distribution. The Pro2b allele was most frequent in Europe and decreased in frequency eastwards. The Pro2f allele occurred frequently in subtropical and tropical regions including the Nansei islands of Japan, the Philippines, Nepal, India, Pakistan and Africa. All eight alleles at the Pro1 and Pro2 loci occurred in China, suggesting China is a center of diversity. The origin of geographical differentiation of local cultivars into a "tropical group" characterized by the Pro2f allele and other genes was discussed.