Comparative analysis of quantitative trait loci for foliage resistance to Phytophthora infestans in tuber-bearing Solanum species

Previously published data for potato foliage resistance to late blight were examined in a combined analysis to determine how the genetic backgrounds of the host and pathogen affect the occurrence of resistance QTLs. Data from 19 diploid populations and one tetraploid population that originated from at least 12 different tuber-bearing Solanum species were included. Comparative analysis across all populations revealed three highly active genomic regions on the distal parts of chromosomes 3, 4, and 5. The region most consistently detected that conferred foliage resistance in Solanum was located on chromosome 5, near marker locus GP21. A previously identified cluster of three race-specific R-genes on chromosome 11 was not associated with polygenic resistance. Statistical examination of active QTLs indicates that congruence among QTLs is significantly affected by both genetic relatedness of mapping populations and race of Phytophthora infestans used for resistance tests. The proportion of congruent QTLs for late blight resistance decreased from 0.52 detected in related Solanum populations tested with the same race of Phytophthora infestans to 0.20 found in unrelated mapping populations tested with different races of Phytophthora infestans. Analysis of resistance mapping tests provided statistical evidence for the occurrence of race-specific QTLs in tuber-bearing Solanum. The highly conserved genomic regions identified in the comparative analysis are likely to be good candidates for gene cloning or marker assisted selection in potato breeding programs.