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 resistanc e currently present in cultivars is insufficient to protect the crop. New s ources of polygenic resistance to Erwinia carotovora ssp, atroseptica (van Hall) Dye (Eca) have been selected in diploid hybrids originating from inte rcrossing 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 constr ucted based on ALFP and RFLP markers including three resistance-gene-like ( RGL) markers. Clustering of AFLP markers in putative centromeric regions wa s 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 chromo somes, The QTL with the largest and most reproducible effect on tuber resis tance mapped to chromosome I. Effects on leaf resistance were less reproduc ible than effects on tuber resistance. Putative QTL, for leaf resistance we re identified on 10 chromosomes. Inheritance of tuber and leaf resistance t o Eca was largely independent. Several QTL for resistance to Eca were linke d to RGL loci. Four of those QTL mapped to genomic segments that have been shown to contain factors for qualitative and quantitative resistance to dif ferent pathogens in potato, tomato (Lycopersicon esculentum Mill.), or toba cco (Nicotiana tabacum L).