DISEASE RESISTANCE IN SOLANUM-PHUREJA AND DIPLOID AND TETRAPLOID SOLANUM-TUBEROSUM X SOLANUM-PHUREJA HYBRIDS

Diploid Solanum phureja, diploid and tetraploid S. tuberosum x S. phur eja hybrid, and tetraploid S. tuberosum backcross clones were assessed for resistance to commercially important diseases. There was a reduct ion in the expression of S. phureja characteristics with increasing do sage of S. tuberosum genetic material. The generally high resistance o f the S. phureja group to common scab, potato leafroll virus and potat o virus Y decreased, while resistance to gangrene, foliage and tuber b light tended to increase. Resistance genes were probably well disperse d throughout the S. phureja genotype so that many were lost on hybridi sation, but S. phureja could be a useful source of scab and virus resi stance in the production of S. tuberosum cultivars.