Background: Raspberry breeding programmes worldwide aim to produce improved cultivars to satisfy market demands and within these programmes there are many targets, including increased fruit quality, yield and season, and improved pest and disease resistance and plant habit. The large raspberry aphid, Amphorophora idaei, transmits four viruses and vector resistance is an objective in raspberry breeding. The development of molecular tools that discriminate between aphid resistance genes from different sources will allow the pyramiding of such genes and the development of raspberry varieties with superior pest resistance. We have raised a red raspberry (Rubus idaeus) F 1 progeny from the cross 'Malling Jewel' × 'Malling Orion' (MJ × MO), which segregates for resistance to biotype 1 of the aphid Amphorophora idaei and for a second phenotypic trait, dwarf habit. These traits are controlled by single genes, denoted (A 1 ) and (dw) respectively.

The distribution of distinct isolates of raspberry bushy dwarf virus (RBDV) in Rubus in England was studied. Isolates similar in Rubus host range to the Scottish type isolate (D200) were largely confined to the old red raspberry (Rubus idaeus) cv. Norfolk Giant, but were also encountered in a single plant of an unidentified raspberry cultivar and in a clump of wild R. idueus. Outside East Malling Research Station (EMRS) RBDV isolates with wider Rubus host ranges than that of the type isolate were found only and exclusively in hybrid berries (Loganberry, clones LY59 and L654, and Tayberry) in which infection ranged from (1% to 100%. The significance of these findings is discussed.

Strong resistance to the cane diseases Elsinoe veneta, Did vmella applanata and Botrvtis cinerea, and to Sphaerotheca macularis, occurred in Fi and BC, derivatives of an accession of Rubus coreanus . Resistance to cane spot (E. veneta) was polygenic .In eight out of ten BC, progenies, average grades for cane spot infections were significantly higher in white-flowered (an,) than pink-flowered (Ani) plants and in hairy-caned (H) than in glabrous (h) seedlings . It is postulated that in . R . coreanus factors controlling resistance are linked with An, and . probably, with h .Average grades for spur blight (D . applanata) were significantly higher in white-flowered plants in nine out of ten BC1 progenies . Spininess (S) was associated with greater susceptibility in six out of eight BC, families, although this difference was not statistically significant .Plants with the phenotype hAn i on average provided the best source of resistance to both cane spot and spur blight .

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