QTL analysis of new sources of resistance to Erwinia carotovora ssp atroseptica in potato done by AFLP, RFLP, and resistance-gene-like markers

The two most important bacterial diseases of cultivated potato, blackleg of stems and tuber soft rot, are caused by Erwinia species. Genetic resistance currently present in cultivars is insufficient to protect the crop. New sources of polygenic resistance to Erwinia carotovora ssp, atroseptica (van Hall) Dye (Eca) have been selected in diploid hybrids originating from intercrossing Solanum tuberosum L with the wild species S. chacoense Bitter and S. yungasense Hawk. One F1 hybrid population derived from these materials was used to locate, on the molecular map of potato, quantitative trait loci (QTL) for resistance of tubers and leaves to Eca. A linkage map was constructed based on ALFP and RFLP markers including three resistance-gene-like (RGL) markers. Clustering of AFLP markers in putative centromeric regions was observed. QTL analysis revealed complex inheritance of resistance to Eca. Genetic factors affecting resistance to Eca were located on all 12 potato chromosomes. Putative QTL for tuber resistance were identified on 10 chromosomes, The QTL with the largest and most reproducible effect on tuber resistance mapped to chromosome I. Effects on leaf resistance were less reproducible than effects on tuber resistance. Putative QTL, for leaf resistance were identified on 10 chromosomes. Inheritance of tuber and leaf resistance to Eca was largely independent. Several QTL for resistance to Eca were linked to RGL loci. Four of those QTL mapped to genomic segments that have been shown to contain factors for qualitative and quantitative resistance to different pathogens in potato, tomato (Lycopersicon esculentum Mill.), or tobacco (Nicotiana tabacum L).