Segregation for resistance to PLRV was evaluated in three families originating from mating of a highly resistant <diploid clone> with <diploid partners>, which differed in their <resistance> to <PLRV>. The virus concentration and external <disease symptoms> in graft-inoculated plants served as criteria of resistance. The mean level of progeny resistance was never inferior to the mid-parent value and usually exceeded it. Some genotypes in the progeny were at least as resistant as their highly resistant parent. Susceptible genotypes were not found in the progeny. The results obtained are consistent with the assumption that a high level of resistance to PLRV is a cumulative effect of dominant genes.