Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/6/2003
Publication Date: 1/8/2004
Citation: Simko, I., Haynes, K.G., Jones, R.W. 2004. Mining data from potato pedigrees: tracking the origin of susceptibility and resistance to Verticillium dahliae in North American cultivars through molecular marker analysis. Theoretical and Applied Genetics. 108:225-230. Interpretive Summary: Verticillium wilt, caused by Verticillium dahliae, is a serious soil-borne pathogen that reduces yield in susceptible potato cultivars by causing early death. We have located a marker that is close to the gene that governs resistance to Verticillium wilt. The ancestry of 139 potato cultivars was traced back through many generations to two potato clones which were used extensively in the early potato breeding program at Beltsville: USDA X96-56 and USDA 41956. This marker was not present in USDA X96-56, which contributed susceptibility to Verticillium wilt in many of its offspring. At least three alleles of this marker were found in USDA 41956, which contributed resistance to Verticillium wilt in many of its offspring. Tetraploid potatoes may have as many as four copies of this allele. Resistance to Verticillium wilt increases with increasing numbers of this allele across all maturity classes, even though earlier maturing cultivars are more susceptible than later maturing cultivars. This information will be useful to breeders in developing Verticillium wilt resistant cultivars and indicates the importance of the allelic composition at this locus for resistance to Verticillium wilt.
Technical Abstract: Potato (Solanum tuberosum L.) cultivated in North America is an autotetraploid species with a narrow genetic base. Most of the popular commercial cultivars are susceptible to Verticillium dahliae, a fungal pathogen causing Verticillium wilt disease, though some cultivars with relatively high resistance also exist. We have used the available pedigree information to track the origin of susceptibility and resistance to Verticillium wilt present in cultivated potatoes. One hundred thirty-nine potato cultivars and breeding selections were analyzed for resistance to the pathogen and for the presence of the microsatellite marker allele STM1051-193 that is closely linked to the resistance QTL located on the short arm of chromosome 9. We detected an unusually high frequency of susceptible genotypes in the progeny descending from the breeding selection USDA X96-56. Molecular analysis revealed that USDA X96-56 does not have the STM1051-193 allele. Most of the first-generation progeny of this breeding selection also lack the allele. On the other hand, pedigree analysis indicated that breeding selection USDA 41956 often transfers V. dahliae resistance to its progeny. Molecular analysis detected presence of (at least) three STM1051-193 alleles in this breeding selection. These two genotypes (USDA X96-56 and USDA 41956) appear to have contributed greatly to the susceptibility or resistance, respectively, found in present commercial cultivars. Our results also indicate that the maturity class substantially affects the plant resistance response. In the intermediate to very late maturing class the presence of the STM1051-193 allele significantly increases the resistance. Early to very early potatoes are usually more susceptible to the disease regardless of the allelic status, though the pattern of the allele effect is always the same. The results indicate that the STM1051-193 allele can be used for the marker-assisted selection, but the potato maturity class also needs to be considered when making the final decision about the plant resistance level. This information can be utilized by breeders to develop marker assisted selection strategies for developing new cultivars with Verticillium wilt resistance.