Submitted to: Plant Breeding
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/1/2006
Publication Date: 8/1/2006
Citation: Simko, I., Costanzo, S., Ramanjulu, V., Christ, B., Haynes, K.G. 2006. Mapping polygenes for tuber resistance to late blight in a diploid Solanum phureja x S. stenotomum hybrid population. Plant Breeding. 125:385-389. Interpretive Summary: Late blight, caused by Phytophthora infestans, is a serious disease of potato foliage and tubers. Genes that confer resistance to foliar late blight in potatoes have been extensively studied. Many such genes have been found. However, information on genes that confer resistance to tuber late blight is very limited. In this study we detected three genes that confer resistance to tuber late blight. These genes are different from the genes that confer foliar resistance. This information will be useful to scientists in developing late blight resistant varieties and in unraveling the genetic mechanisms involved in host plant resistance.
Technical Abstract: Potato tuber blight is a disease caused by the oomycete Phytophthora infestans (Mont.) de Bary. Due to the significant economic impact of this disease, introgression of durable resistance into the cultivated potato is one of the top priorities of breeding programs worldwide. Though numerous resistance loci against this devastating disease have already been mapped, most of the detected loci are contributing towards foliar resistance while specific information on tuber resistance is limited. To identify the genetic components of tuber resistance and its relationship to foliar resistance and plant maturity we have investigated the host-pathogen interaction in a segregating diploid hybrid Solanum phureja × S. stenotomum family. Mature tubers from this mapping family were inoculated with a sporangial suspension of P. infestans (US-8 clonal lineage) and evaluated for lesion expansion. No significant correlation was detected between late blight resistance in foliage and tubers, and between plant maturity and tuber resistance. Four chromosomal regions were significantly associated with tuber resistance to the disease. The largest effect was detected near the marker locus PSC (LOD 10.7) located on chromosome 10. This locus explained about 63% of the total phenotypic variation of the trait. The other three resistance-related loci were mapped on chromosomes 8 (GP128-2, LOD 4.4), 6 (CP18, LOD 4.0), and 2 (CP157, LOD 3.8). None of the four tuber resistance loci coincides with the foliage resistance loci detected in this same family. Tuber blight resistance QTLs on chromosomes 2, 8, and 10 are distinct from the maturity QTLs and have an additive effect on tuber resistance. These results indicate that different genes are involved in foliar and tuber resistance to P. infestans in the present family and that some of the resistance genes might be associated with late maturity.