RESISTANCE TO LATE BLIGHT IN POTATO - A PUTATIVE GENE THAT SUPPRESSESR-GENES AND IS ELICITED BY SPECIFIC ISOLATES

Eleven progenies, ten bi-parental and one selfed, of tetraploid potato were assessed for phenotypic segregation ratios of resistance to susc eptible individuals against two isolates of P. infestans, one avirulen t to all 11 known potato R genes (avirulent pathotype) and one virulen t to eight R genes (virulent pathotype). Assuming Mendelian inheritanc e of independent R genes, the numbers of individuals segregating for r esistance to both races could not be explained sufficiently for all pr ogenies. However, the assumed presence of dominant, specific suppresso rs of the R gene function that were elicited by specific isolates of t he fungus and that segregated in the host independently from R genes e xplained all frequencies of resistant and susceptible individuals in e ach of the progenies studied.