Segregation analysis and RFLP mapping of the R1 and R3 alleles conferring race-specific resistance to Phytophthora infestans in progeny of dihaploid potato parents

Abstract

Phytophthora infestans (Mont.) de Bary is the most important fungal pathogen of the potato (Solanum tuberosum). The introduction of major genes for resistance from the wild species S. demissum into potato cultivars is the earliest example of breeding for resistance using wild germplasm in this crop. Eleven resistance alleles (R genes) are known, differing in the recognition of corresponding avirulence alleles of the fungus. The number of R loci, their positions on the genetic map and the allelic relationships between different R variants are not known, except that the R1 locus has been mapped to potato chromosome V. The objective of this work was the further genetic analysis of different R alleles in potato. Tetraploid potato cultivars carrying R alleles were reduced to the diploid level by inducing haploid parthenogenetic development of 2n female gametes. Of the 157 isolated primary dihaploids, 7 set seeds and carried the resistance alleles R1, R3 and R10 either individually or in combinations. Independent segregation of the dominant R1 and R3 alleles was demonstrated in two F1 populations of crosses among a dihaploid clone carrying R1 plus R3 and susceptible pollinators. Distorted segregation in favour of susceptibility was found for the R3 allele in 15 of 18 F1 populations analysed, whereas the R1 allele segregated with a 1:1 ratio as expected in five F1 populations. The mode of inheritance of the R10 allele could not be deduced as only very few F1 hybrids bearing R10 were obtained. Linkage analysis in two F1 populations between R1, R3 and RFLP markers of known position on the potato RFLP maps confirmed the position of the R1 locus on chromosome V and localized the second locus, R3, to a distal position on chromosome XI.

Characterization and high-resolution mapping of a late blight resistance locus similar to R2 in potato

“…A detached leaf assay with P. infestans isolate 90128 revealed 24 resistant and 45 susceptible genotypes, which fits to a 1-2 segregation according to the v 2 test. This segregation is skewed to susceptible, which might be caused by the relatively small population size or by postzygotic selection against unfavourable allelic combinations El-Kharbotly et al 1994). Nine genotypes were not assigned due to unclear observation.…”

“…Several R genes have been localized, e.g. R1 on chromosome 5 (Leonards-Schippers et al 1992) and R3, R6 and R7 clustered on chromosome 11 (El-Kharbotly et al 1994. R1 and R3 have been isolated (Ballvora et al 2002;Huang 2005).…”

The novel, major locus Rpi-phu1 for late blight resistance maps to potato chromosome IX and is not correlated with long vegetation period

“…R2 was localized on chromosome IV (Li et al 1998). Genes R3, R6 and R7 were all mapped to a distal position on chromosome XI (El-Kharbotly et al 1994. Fine mapping of R3 revealed that this resistance is in fact conferred by two closely linked genes R3a and R3b with distinct pathogen speciWcities (Huang et al 2004.…”

“…Soon afterwards, some of them have been introduced into potato cultivars (Niederhauser et al 1954;Stewart and Bradshaw 2001). The Wrst gene for late blight resistance that was mapped and subsequently cloned in potato is R1 on chromosome V ( Leonards-Schippers et al 1994;Ballvora et al 2002). Other R genes originating from S. demissum were mapped to diVerent positions.…”

Evolution and Management of the Irish Potato Famine Pathogen Phytophthora Infestans in Canada and the United States

“…Initially, a total of 11 R genes (R1-R11) from Solanum demissum were characterized for potatoes ( Table 2). Most of these R genes, R3 through R11 were mapped to chromosome 11 (Bradshaw et al 2006;El-Kharbotly et al 1994;Huang et al 2004Huang et al , 2005, while R1 (El-Kharbotly et al 1994), R2 (Li et al 2008), and R8 (Jo et al 2011) were mapped to chromosomes 5, 4, and 8, respectively. These R genes were introduced into cultivated varieties worldwide.…”