RESISTANCE TO GLOBODERA-ROSTOCHIENSIS (WOLL) PATHOTYPE ROL IN SELECTED PROGENIES OF SOME CULTIVARS OF SOLANUM-TUBEROSUM L

The inheritance of resistance to Globodera rostochiensis pathotype Ro1 was studied in progenies of 10 selected cultivars which had resistance to different pathotypes, stemming from several wild species. Progenies of all the cultivars were produced by crossing with a susceptible cultivar, and several random samples from each combination, usually progeny from a single berry, were tested for their resistance to pathotype Ro1. The cultivars could be separated into genotypic groups, according to the proportion of resistant progeny in each combination. Cultivars which did not differ significantly in the split of resistant and susceptible progenies, but were clearly different from other groups, were put in the same group. The number of groups which could be differentiated was not consistent with the theoretically possible genotype, simplex ... quadruplex, arising from the inheritance of the gene H-1. Greater genetic variation could be detected involving more than 4 genotypic groups. The results suggest the existence of another genetical mechanism. The number of groups and their reproducibility requires further investigation. It will therefore be necessary to test several different random samples to characterise a single combination.