Mapping of the gene Nxphu that controls hypersensitive resistance to potato virus X in Solanum phureja lvP35

The line IvP35 of the diploid (2n = 2x = 24) cultivated potato species Solanum phureja (family Solanaceae) expresses hypersensitive resistance (H) to potato X potexvirus (PVX). In this study, a diploid potato population was produced using IvP35 as the male parent and a diploid line of S. tuberosum (87HW13.7) as the female parent and tested for resistance to PVX. Data indicated that H to PVX in IvP35 is a dominant, monogenically inherited trait controlled by a single gene, named Nx(phu), that is in a simplex condition (Nxnx). RFLP analysis carried out on the progeny lines revealed 4 markers (CT220, TG328, CT112 and TG424) from the long arm of chromosome IX that were linked to the hypersensitive phenotype; the closest linkage was observed with the marker TG424. Previous authors have shown that the same region of chromosome IX contains the gene Sw-5 for resistance to tomato spotted wilt tospovirus in Lycopersicon peruvianum (Solanaceae).