Mapping the H2 resistance effective against Globodera pallida pathotype Pa1 in tetraploid potato

Key message The nematode resistance gene H2 was mapped to the distal end of chromosome 5 in tetraploid potato. Abstract The H2 resistance gene, introduced into cultivated potatoes from the wild diploid species Solanum multidissectum , confers a high level of resistance to the Pa1 pathotype of the potato cyst nematode Globodera pallida . A cross between tetraploid H2 -containing breeding clone P55/7 and susceptible potato variety Picasso yielded an F1 population that segregated approximately 1:1 for the resistance phenotype, which is consistent with a single dominant gene in a simplex configuration. Using genome reduction methodologies RenSeq and GenSeq, the segregating F1 population enabled the genetic characterisation of the resistance through a bulked segregant analysis. A diagnostic RenSeq analysis of the parents confirmed that the resistance in P55/7 cannot be explained by previously characterised resistance genes. Only the variety Picasso contained functionally characterised disease resistance genes Rpi - R1 , Rpi - R3a , Rpi - R3b variant, Gpa2 and Rx , which was independently confirmed through effector vacuum infiltration assays. RenSeq and GenSeq independently identified sequence polymorphisms linked to the H2 resistance on the top end of potato chromosome 5. Allele-specific KASP markers further defined the locus containing the H2 gene to a 4.7 Mb interval on the distal short arm of potato chromosome 5 and to positions that correspond to 1.4 MB and 6.1 MB in the potato reference genome.