Resistance to potato viruses M,S, X and the spindle tuber virus in tuber-bearingSolanum species

On two separate occasions, some available accessions of tuber-bearingSolanum species were tested for resistance to potato viruses. Challenge inoculations were made mechanically with infective sap; and assessment was by sub-inoculation to differential host plants, supplemented by serological tests. In 1956–57, four accessions remained free from potato virus S (PVS), and nine remained free from PVM. In 1968–70, one or more clones of 11 accessions showed resistance to PVS—one of them,S. megistacrolobum, a diploid, apparently being hypersensitive. Resistance to PVX was found in seven accessions, and to PVM in two. There appeared to be resistance to the potato spindley tuber virus in five accessions.