The Distribution, Abundance, and Genetic Relationships of Four Strains of the Rubus Aphid (Amphorophora Rubi (Kalt.)) in Relation To Raspberry Breeding

Field collections of Amphorophora rubi (Kalt.), the rubus aphid, from 28 localities were classified into strains by their reaction to the raspberry varieties Mailing Landmark and Seedling 136/2, the former being resistant to strains 1 and 3 of the aphid, and the latter to strain 2. A new strain, numbered 4, was isolated, capable of breeding on both varieties, and it was found that the field distribution of this strain and of strain 2 was closely linked with the variety Landmark.Strains 2 and 4 appeared to have low fertility when inbred and, after a year of rearing in captivity, were all found to be homozygous for the genes conditioning their host plant reaction. Hybridization of strains 2 and 3 led to increased fertility and to the production, in the F2, of strain 4 types. An hypothesis postulating single-gene control of the ability to colonize Landmark and 136/2 is advanced and genotypes for the four strains are suggested.The implications of the discovery of strain 4 for plant breeding for resistance usi...