VARIABILITY IN THE WILD RASPBERRY

S ummary Surveys of wild raspberries in Europe and Britain, and of progenies raised from seed collected in the wild, showed widespread polymorphism for the gene H (hairy/subglabrous canes) and less frequent polymorphism for P (spine colour intensifier). No yellow fruited ( t ), spineless ( s ) or sepaloid ( sx 3 ) plants were seen. Breeding experiments snowed there was no close linkage between H and the incompatibility S locus. Male sterility occurred in three out of nineteen progenies and partial female sterility, accompanied by abnormalities affecting vegetative characters, segregated in three out of eleven progenies from sibbing four seedlings. This condition was due to a semi‐lethal gene, gr . Progenies varied widely in response to powdery mildew ( Sphaerotheca macularis (Fr.) Jaczewski), from 0 to 100% of seedlings proving resistant. The incidence of resistance in progenies tended to increase with increasing altitudinal origin of the parent, total percentage resistance in all progenies being 6.6, 59.6, 64.3 and 97.2 for parental altitudes of less than 500 m, 500–1000 m, 1000–1500 m and over 1500 m, respectively. It is suggested that higher mildew resistance may be a secondary effect of greater cold hardiness at high altitudes. Resistance to the aphid Amphorophora rubi occurred in seventeen out of twenty‐eight wild progenies. Resistance to strain 3 of the aphid was more common than to strain 2; in both cases, the incidence of resistance tended to decrease with increasing altitude of the parent. Only one very small progeny was homozygous for resistance. Resistant and susceptible classes were usually sharply differentiated, indicating the segregation of major resistance genes. Genes conferring, respectively, strain 2 resistance alone, strain 3 resistance alone and resistance to both strains, were isolated.