Submitted to: American Journal of Potato Research
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/17/2001
Publication Date: N/A
Citation: Interpretive Summary: Resistance to potato tuber soft-rot, a bacterial disease, was transferred from a wild species into cultivated potatoes via a cell fusion technique. A new assay for the disease is described. The newly resistant potato plants showed a 20 % decrease in the proportion of diseased tubers. DNA markers indicated that more than one gene was responsible for resistance. Inheritance of resistance was stable for at least four generations. Other scientists will benefit from this information as they use the resistant plants in their potato breeding programs. Because some chromosomal regions are unstable in somatic hybrids, the markers provided in this paper will allow breeders to follow the resistance from one generation of plants to the next.
Technical Abstract: Resistance to potato tuber soft rot caused by Erwinia carotovora was transferred from Solanum brevidens to the cultivated potato over the course of four backcross generations originating from a somatic hybrid. Soft rot reactions were determined via a tuber plug inoculation method developed during the course of these experiments. Soft rot resistance was highest in the somatic hybrid (only ca. 20% of tubers and plugs showed evidence of severe rotting) and lowest among progeny of control potato x potato crosses (ca. 80% of tuber plugs showed severe rot). Backcross generations involving somatic hybrids were intermediate in their reaction, and resistance stabilized to about 60% of tuber plugs showing severe rot in the BC2 through the BC4. Reciprocal crosses showed no difference in the inheritance of soft rot resistance, indicating that neither S. brevidens nor S. tuberosum donor cytoplasm had a significant effect on the expression of resistance. Crosses between BC3 siblings where no S. brevidens genetic markers were detected but resistance was segregating demonstrated a dosage effect for soft rot resistance. We conclude that introgression of soft rot resistance has occurred and that at least one locus responsible for resistance in S. brevidens now resides in the S. tuberosum genome.