Abstract
BackgroundPhytophthora infestans (Mont.) de Bary, the causal organism of late blight, is economically the most important pathogen of potato and resistance against it has been one of the primary goals of potato breeding. Some potentially durable, broad-spectrum resistance genes against this disease have been described recently. However, to obtain durable resistance in potato cultivars more genes are needed to be identified to realize strategies such as gene pyramiding or use of genotype mixtures based on diverse genes.ResultsA major resistance gene, Rpi-rzc1, against P. infestans originating from Solanum ruiz-ceballosii was mapped to potato chromosome X using Diversity Array Technology (DArT) and sequence-specific PCR markers. The gene provided high level of resistance in both detached leaflet and tuber slice tests. It was linked, at a distance of 3.4 cM, to violet flower colour most likely controlled by the previously described F locus. The marker-trait association with the closest marker, violet flower colour, explained 87.1% and 85.7% of variance, respectively, for mean detached leaflet and tuber slice resistance. A genetic linkage map that consisted of 1,603 DArT markers and 48 reference sequence-specific PCR markers of known chromosomal localization with a total map length of 1204.8 cM was constructed.ConclusionsThe Rpi-rzc1 gene described here can be used for breeding potatoes resistant to P. infestans and the breeding process can be expedited using the molecular markers and the phenotypic marker, violet flower colour, identified in this study. Knowledge of the chromosomal localization of Rpi-rzc1 can be useful for design of gene pyramids. The genetic linkage map constructed in this study contained 1,149 newly mapped DArT markers and will be a valuable resource for future mapping projects using this technology in the Solanum genus.
Highlights
Phytophthora infestans (Mont.) de Bary, the causal organism of late blight, is economically the most important pathogen of potato and resistance against it has been one of the primary goals of potato breeding
Cvs Sárpo Mira and Robijn and clone DG 94-15 showed some level of resistance to P. infestans (Table 2)
The distributions of the mean detached leaflet and tuber slice resistances in the mapping population were bimodal and significantly deviated from normality, which was confirmed by the KolmogorovSmirnov test (Figure 2)
Summary
Phytophthora infestans (Mont.) de Bary, the causal organism of late blight, is economically the most important pathogen of potato and resistance against it has been one of the primary goals of potato breeding. Some potentially more durable, broad-spectrum R genes have recently been described, including RB/Rpi-blb1 [4,5], Rpi-blb3 [6], Rpivnt1.1 [7,8], Rpi-phu1 [9] and Rpi-sto1 [10] New strategies preventing such rapid evolution of compatible P. infestans races have been proposed. All these are based on avoiding monocultures and use of as many broad-spectrum R genes as possible. These can either be stacked within cultivars or used in mixtures of breeding lines each containing a different R gene. To improve the likelihood that these strategies will be successful, breeders need to have many such genes available and the search for these continues among wild relatives of potato
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