Genetic analysis of potato (Solanum species) genotypes using morphological and molecular markers

English: Genetic analysis of 53 potato genotypes representing seven of the 13 potato species that are frequently used in the varietal development of potato was examined using morphological and molecular markers with main objective of analyzing their genetic distance and evolutionary relationships. These genotypes were obtained from the Ethiopian National Potato Research Program and the ARC-Roodeplaat Vegetable and Ornamental Plant Institute of South Africa. These species are collections from the major diversity centres of potato, i.e., Peru, Argentina, Mexico and Bolivia. They include both wild and cultivated diploid and tetraploid genotypes. Of the 53 genotypes only 15 genotypes consisting 11 advanced breeding clones and Ethiopian converted commercial tetraploid varieties were examined morphologically. As a result a genetic distance ranging from 0.46 to 1.68 was computed. This clearly indicates the phenotypic diversity existing .among them and the diverse genetic background of their parental materials. A direct positive correlation was found between stem height and weight of tuber and days to flowering and days to harvesting as previously reported and negative associations between number of tubers per plant and average weight of a tuber and leaflet width and days to flowering. AFLP and SSR analysis of these genotypes together with 38 other genotypes of different species supported the phenotypic diversity result with a genetic distance value ranging from 0.28 to 0.70 for AFLP and 0.28 to 0.78 for SSR. As expected the genetic distance computed using molecular data are more conservative in their estimate than those computed using morphological data. Furthermore, AFLP and SSR data revealed that Solanum stenotomum and Solanum sparsipilum might be the putative ancestor of the cultivated potato Solanum tuberosum subsp. andigena as previously hypothesized. However, the grouping of species based on DNA does not always indicate ancestry but is rather a result of introduced traits from wild species. This data clearly indicated those species that have contributed genes to potato cultivars thus far developed. Hence, with the use of morphological markers that are heritable and stable genetic distance could be successfully studied. This, however, does not rule out the major drawbacks of morphological markers caused by the low level of heritable and stable characters. In conclusion, this study has revealed the relevance of employing morphological markers together with molecular markers to determine genetic distances for potato breeding. Although there were differences in the ranges of genetic distances calculated using the different markers, there was a remarkable correlation between the relationships of the different genoptypes based on these distances. Hence, DNA marker systems with high multiplex ratio like AFLP and high diversity index like SSR can be an excellent component to the morphological and conventional markers that are currently used to estimate genetic diversity or distance and evolutionary relationships for potato.