QTL for resistance to Globodera rostochiensis pathotype Ro2 and G. pallida pathotype Pa2/3 in autotetraploid potato

Authors: PARK, JAEBUM - Cornell University; HACKETT, CHRISTINE - Biomathematics And Statistics Scotland (BIOSS); DANDURAND, LOUISE-MARIE - University Of Idaho; Wang, Xiaohong; DEJONG, WALTER - Cornell University

Submitted to: American Journal of Potato Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/12/2019
Publication Date: 11/22/2019
Citation: Park, J., Hackett, C.A., Dandurand, L., Wang, X., Dejong, W.S. 2019. QTL for resistance to Globodera rostochiensis pathotype Ro2 and G. pallida pathotype Pa2/3 in autotetraploid potato. American Journal of Potato Research. https://doi.org/10.1007/s12230-019-09745-4.
DOI: https://doi.org/10.1007/s12230-019-09745-4

Interpretive Summary: Potato cyst nematodes (Globodera rostochiensis and G. pallida) are quarantine pests that can cause greater than 60% potato yield reduction if not controlled. The Ro2 pathotype of G. rostochiensis (golden nematode), which can infect potato cultivars containing the H1 resistance gene, has been detected on New York potato farms. The emergence of Ro2 poses a serious threat to the success of the G. rostochiensis quarantine in NY; there is a critical need to develop potato varieties that are resistant to Ro2. Identifying genes or quantitative trait loci (QTL) that confer resistance against Ro2 would accelerate breeding. In this study, a mapping population of 182 offspring was obtained by crossing the breeding clone NY121, which is Ro2 resistant, with breeding clone NY115, which is Ro2 susceptible. The offspring of this cross were evaluated for Ro2 resistance and genotyped with SNP (single nucleotide polymorphism) markers. Combined analysis of the marker and resistance data revealed that two regions on chromosome 5 provided resistance against Ro2. One of these regions also conferred resistance to G. pallida. We hypothesize that the gene(s) that confers resistance against both Ro2 and G. pallida may correspond to Grp1, a previously described QTL that confers resistance to both PCN species. Marker-assisted selection for Grp1 may facilitate breeding for PCN resistance.

Technical Abstract: The golden and white potato cyst nematodes (Globodera rostochiensis and G. pallida, respectively) are devastating quarantine pests of potatoes. The most widely distributed pathotype of the golden nematode, Ro1, is well controlled by the H1 resistance gene. A pathotype that overcomes H1, Ro2, has been detected on several farms in New York State. To map Ro2 resistance gene(s), two autotetraploid parental clones – NY121 (Ro2 resistant) and NY115 (susceptible) – along with 182 F1 offspring were genotyped with 8303 SNP markers, and the resistance of each clone to Ro2 was assessed with a greenhouse pot assay. Analyses with TetraploidSNPMap identified two Ro2 resistance QTL on chromosome 5: one QTL was located at 26 cM and explained 24% of the variation for resistance, while the second at 59 cM co-localized with a marker (57R) known to be tightly linked to H1 and explained 13% of the variation. Subsequent bioasssay of G. pallida revealed that the locus at 26 cM was also effective against pathotype Pa2/3, explaining 9.2% of the variation while a second QTL that increased susceptibility to Pa2/3 was located at 15 cM on chromosome 10, explaining 6.9% of the variation. The resistance gene(s) at 26 cM on chromosome 5 may correspond to previously described Grp1; a marker diagnostic for this region would be useful for applied potato breeding.