| Germplasm from wild Solanum species has contributed numerous beneficial traits to cultivated potato. However, much of this diverse germplasm has not been utilized due to difficult crossing barriers and a lack of understanding of the syntenic relationships among Solanum species. Modern knowledge of how to circumvent crossing barriers has broadened the possibilities for the utilization of this germplasm.; Late blight of potato, caused by Phytophthora infestans (Mont.) DeBary, has been a devastating potato production problem since the Irish Potato Famine in the 1840s. Since no control agent exists that can stop an established infection, host plant disease resistance is an attractive solution. Many late-blight resistance genes have been introgressed into S. tuberosum from S. demissum and systematically overcome by the pathogen. Recent work has identified late-blight resistance in several Mexican diploid Solanum species raising questions about the syntenic relationships of late-blight resistance loci in S. demissum and Mexican diploid Solanum species.; Phytophthora infestans isolate MSU96 (US8-A2) reveals resistance in the late-blight differential R9-Hodgson 2573 (LB3) and S. pinnatisectum. To determine the syntenic relationship between these two phenotypes, a cross of LB3 by susceptible Ranger Russet yielded an F1 mapping population segregating for one dose of the resistance allele. Restriction fragment length polymorphisms showed no association between the late-blight resistance on chromosome seven of S. pinnatisectum (R pil) and R9. There was also no linkage between R9 and other chromosome positions known to carry resistance loci. These results indicate that Rpil and R9 are non-syntenic and that R9 likely maps to a chromosome region not previously associated with disease resistance in potato.; As pathogen populations continue to evolve, a diversity of resistance genes is necessary to provide disease control. Sometimes the resistances reside in germplasm sources that are difficult to utilize, such as with Rpil. We attempted crosses of S. pinnatisectum with "bridge species" S. verrucosum and haploids of S. tuberosum to begin introgression of R pil to cultivated potato. Embryo rescue and 2,4-dichlorophenoxyacetic acid treatments were used to circumvent barriers caused by differences in EBN. We were unable to produce any hybrids between S. pinnatisectum clone 5JK1D and the other Solanum species. |
