MEIOSIS IN TWO MEXICAN AND TWO SOUTH AMERICAN WILD DIPLOID POTATOES

More than 70 percent of wild relatives of Potato (Solanum tuberosum L.) with a wide range of geographical distribution are diploids. These species are main resources of valuable genes for potato breeding programs. In this study, we evaluated the meiosis in diploid potatoes with different geographic origins (two species from Mexico (S. bulbocastanum and S. pinnatisectum) and two species from South America (S. commersonii and S. chacoense). Chromosomes pairing in Metaphase I, as expected in diploid species, were predominately bivalent, while in all of four investigated species, univalent pairing was also observed with very low frequency. The highest frequency of univalents observed in S. commersonii. Tetravalent observed only in S. bulbocastanum (0.07%). Microsporocytes with laggard chromosomes or chromatids were observed more or less in Anaphase I, and II in all species. This abnormality in S. commersonii was more than that of other species. By the way with regard to low incidence of tetrads with micronuclei in sporad, it is concluded that laggard chromosomes finally reached them to the respective nuclei. Overly results showed that the studied species from cytological point of view were true diploid and retained the integrity of its genome and there is no evidence of recent hybridity in them.