Molecular characterisation of resistance against potato wart races 1, 2, 6 and 18 in a tetraploid population of potato (Solanum tuberosum subsp. tuberosum)

Potato wart is caused by the obligate biotrophic fungus Synchytrium endobioticum, which is subject to quarantine regulations due to the production of long persisting spores in the soil and the lack of effective fungicides. The objective of this study was to identify quantitative trait loci (QTL) for resistance against potato wart races (R) 1, 2, 6 and 18 in a tetraploid potato population developed by crossing cv. Saturna (resistant to R1) with cv. Panda (resistant to R1, R2, R6, R18). A total of 92 progenies were used for phenotyping and genotyping. Resistance tests were performed for races 1 and 18 in 2 years and for races 2 and 6 in 1 year on 10 to 20 eyepieces per genotype. Based on amplified fragment length polymorphism (AFLP) and simple sequence repeat (SSR) markers, linkage maps were established for the female and male parent, respectively. Single marker analysis followed by a multiple regression analysis revealed initial marker–trait associations. The interval mapping routine of TetraploidMap was applied for QTL analysis. A major QTL for resistance against race 1 explaining between 46 % and 56 % of the phenotypic variation was identified near Sen1, a known resistance locus for potato wart race 1 on chromosome XI. Other resistance QTL were detected on chromosomes I (to R2), II (to R6, 18), VI (to R1, 2, 6, 18), VII (to R2, 6, 18), VIII (to R1, 2, 6, 18), X (to R2, 6, 18), XI (to R2, 6, 18) and on an unknown linkage group (to R18) explaining minor to moderate effects of the phenotypic variation. Resistance QTL against different potato wart races often overlapped, particularly concerning races 2, 6 and 18. Overall, this study gives a valuable insight into the complex inheritance of resistance against potato wart.