Stability of late blight resistance of potato hybrids with diverse genetic background

Nine clones of interspecies potato hybrids and cv. Nayada recommended for cultivating on the territory of the northwestern Russia were tested for nine years under different infection loads in the field and following twice repeated artificial infection with a highly aggressive isolate of Phytophthora infestans. Stable resistance to late blight (LB) in the field through the entire period of observations was registered only in clone 99-4-1, meanwhile the responses of other genotypes varied depending on the year of the test. The results of the tests under natural and artificial infection when compared by the average degree of consistency (Kendall’s W = 0.43) did not concur perfectly indicating that a comprehensive assessment is necessary. In the best characterized clones 171-3 and 99-4-1 comprising the genetic material of S. anigenum, S. demissum and S. stoloniferum, only two race-specific resistance genes were found: R1 and R3b presuming that further study of the genetic nature of LB resistance in the interspecific hybrids is on the agenda.