RESUMO
Despite efforts to control late blight in potatoes by introducing R(pi)-genes from wild species into cultivated potato, there are still concerns regarding the durability and level of resistance. Pyramiding R(pi)-genes can be a solution to increase both durability and level of resistance. In this study, two resistance genes, R(Pi-mcd1) and R(Pi-ber), introgressed from the wild tuber-bearing potato species Solanum microdontum and S. berthaultii were combined in a diploid S. tuberosum population. Individual genotypes from this population were classified after four groups, carrying no R(pi)-gene, with only R (Pi-mcd1), with only R(Pi-ber), and a group with the pyramided R(Pi-mcd1) and R (Pi-ber) by means of tightly linked molecular markers. The levels of resistance between the groups were compared in a field experiment in 2007. The group with R(Pi-mcd1) showed a significant delay to reach 50% infection of the leaf area of 3 days. The group with R ( Pi-ber ) showed a delay of 3 weeks. The resistance level in the pyramid group suggested an additive effect of R (Pi-mcd1) with R(Pi-ber). This suggests that potato breeding can benefit from combining individual R(pi)-genes, irrespective of the weak effect of R(Pi-mcd1) or the strong effect of R(Pi-ber).
Assuntos
Genes de Plantas , Imunidade Inata/genética , Phytophthora infestans/imunologia , Doenças das Plantas , Solanum tuberosum , Cruzamento , Produtos Agrícolas/genética , Produtos Agrícolas/microbiologia , DNA de Plantas/genética , Ligação Genética , Marcadores Genéticos , Dados de Sequência Molecular , Phytophthora infestans/patogenicidade , Doenças das Plantas/genética , Doenças das Plantas/imunologia , Doenças das Plantas/microbiologia , Solanum tuberosum/genética , Solanum tuberosum/microbiologiaRESUMO
The distinction between field resistance and resistance based on resistance (R) genes has been proven valid for many plant-pathogen interactions. This distinction does not seem to be valid for the interaction between potato and late blight. In this study, a locus involved in late blight resistance, derived from Solanum microdontum, provides additional evidence for this lack of distinction. The resistance is associated with a hypersensitive response and results in a delay of infection of approximately 1 to 2 weeks. Both a quantitative as well as a qualitative genetic approach were used, based on data from a field assay. Quantitative trait locus (QTL) analysis identified a QTL on chromosome 4 after correction of the resistance data for plant maturity. A qualitative genetic analysis resulted in the positioning of this locus on the short arm of chromosome 4 in between amplified fragment length polymorphism marker pCTmACG_310 and cleaved amplified polymorphic sequence markers TG339 and T0703. This position coincides with a conserved Phytophthora R gene cluster which includes R2, R(2-like), R(Pi-blb3), and R(Pi-abpt). This implies that R(Pi-mcd1) is the fifth R gene of this nucleotide-binding site leucine-rich repeat cluster. The implications of our results on R-gene-based and field resistance are discussed.