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

[摘要] English: Genetic analysis of 53 potato genotypes representing seven of the 13 potato species that arefrequently used in the varietal development of potato was examined using morphological andmolecular markers with main objective of analyzing their genetic distance and evolutionaryrelationships. These genotypes were obtained from the Ethiopian National Potato ResearchProgram 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 andEthiopian converted commercial tetraploid varieties were examined morphologically. As aresult a genetic distance ranging from 0.46 to 1.68 was computed. This clearly indicates thephenotypic diversity existing .among them and the diverse genetic background of theirparental materials. A direct positive correlation was found between stem height and weight oftuber and days to flowering and days to harvesting as previously reported and negativeassociations between number of tubers per plant and average weight of a tuber and leafletwidth and days to flowering.AFLP and SSR analysis of these genotypes together with 38 other genotypes of differentspecies supported the phenotypic diversity result with a genetic distance value ranging from0.28 to 0.70 for AFLP and 0.28 to 0.78 for SSR. As expected the genetic distance computedusing molecular data are more conservative in their estimate than those computed usingmorphological data. Furthermore, AFLP and SSR data revealed that Solanum stenotomumand Solanum sparsipilum might be the putative ancestor of the cultivated potato Solanumtuberosum subsp. andigena as previously hypothesized. However, the grouping of speciesbased on DNA does not always indicate ancestry but is rather a result of introduced traitsfrom wild species. This data clearly indicated those species that have contributed genes topotato cultivars thus far developed. Hence, with the use of morphological markers that areheritable 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 heritableand stable characters.In conclusion, this study has revealed the relevance of employing morphological markerstogether with molecular markers to determine genetic distances for potato breeding.Although there were differences in the ranges of genetic distances calculated using thedifferent markers, there was a remarkable correlation between the relationships of thedifferent genoptypes based on these distances. Hence, DNA marker systems with highmultiplex ratio like AFLP and high diversity index like SSR can be an excellent component tothe morphological and conventional markers that are currently used to estimate geneticdiversity or distance and evolutionary relationships for potato.

[发布机构] University of the Free State