Transfer of a new PVX resistance gene from Solanum commersonii to S. tuberosum through somatic hybridization

The tetraploid somatic hybrid SH9A, obtained by protoplast fusion of the accession PI 243503 of Solanum Commersonii (2n=2x=24, EBN=1) and the dihaploid potato clone SVP11 (2n=2x=24, EBN=2), was evaluated for resistance to potato virus X (PVX). The inheritance of resistance to PVX was also determined in the SH9A self-pollinated progenies. The accession PI 243503 of S. commersonii (cmm) had been previously found to be resistant to potato PVX, but this resistance source has not been further exploited since cmm is not crossable either with tetraploid or dihaploid Solanum tuberosum (tbr). After mechanical inoculation of the virus, all SH9A and cmm plants were found to be resistant to PVX as demonstrated by DAS-ELISA test and by back-inoculations on Gomphrena globosa. The resistance to PVX transferred to the somatic hybrid seems to be of the 'extreme type' since it was not possible to detect the virus by ELISA test in the inoculated leaves and recover the virus by back-inoculation onto G. globosa. Virtually all selfed progenies of the somatic hybrid were resistant, suggesting homozygosity for a dominant gene in the wild parent and disomic inheritance in the genotypes analyzed.