SUMMARYNewly‐opened strawberry flowers of several cultivars were inoculated in the glasshouse, growth chamber and field with conidia of Botrytis cinerea from cultures of seven isolates. Infection in pistils, stamens, petals, sepals and receptacles was detected by u.v. microscopy after softening fixed tissues in 1 N sodium hydroxide and staining in 0–1% aniline blue. For all isolates, cultivars and environments, conidia germinated on the stigmas and their hyphae grew into the transmitting tissue of the styles, but so slowly that they sometimes took 4–6 wk to reach the style bases. Cv. Troubadour was the only cultivar in which hyphae grew from the style into the carpel, but growth there was limited and did not progress into the receptacle. The fungus produced conidiophores and conidia on the stigmas of 15 of the 23 cultivars tested in the field but did not do so in the growth chamber or glasshouse tests. It readily colonised the anthers and connective between the anther lobes and sporulated on anthers in the field; in some cultivars it grew to the base of a few stamen filaments and into the receptacle. In the glasshouse, conidia remained ungerminated on the petals and sepals for at least 6 days, but in a moist chamber they germinated and hyphae rapidly penetrated the epidermis and colonised internal tissues of these flower parts. Results indicated that stamens may be more important than styles as a source of latent infection.

RAPD markers were generated from 13 different Rubus species in order to assess the degree of similarity between species from the important subgenera. All ten primers revealed scorable polymorphisms within both the closely related and the genetically diverse individuals. Three hundred and seventy-two markers were generated and scored from the material analysed. Estimates of similarity, dendrograms and principle co-ordinate analysis were calculated, with the results generally being in agreemen with previous classifications of the species studied, confirming the validity and usefulness of the RAPD method. However, amongst the species studied, R. macraei of the Idaeobats proved more diverse and grouped in with both the Idaeobats and Eubats at only 26% similarity.

Pedigrees of 137 red raspberry (Rubus idaeus L.) varieties released throughout the world since 1960 were used to calculate: 1) the genetic contribution of founding clones to these varieties; 2) genetic relatedness among them; and 3) their inbreeding coefficients. Fifty founding clones contributed to the pedigrees of these varieties with a mean genetic contribution ranging from <0.1% to 21%. Varieties were clustered according to the genetic contribution into groups strongly related to geographical origin. Varieties developed in the former USSR and derived from `Novost Kuzmina' formed a distinct cluster. The remaining varieties were clustered in groups based mainly on whether they were of North American or European origin. Varieties were clustered also on the basis of Wright's coefficient of relationship-a measure of genetic relatedness. Cluster groups were related to their geographical origin and the varieties within the groups could be traced to similar intermediate parents. Inbreeding coefficients ranged from 0.0 to 0.625 and were related, in part, to the numbers of generations of controlled hybridization from common ancestors. The British group, with the largest number of generations of breeding, had a low mean inbreeding coefficient, indicating that inbreeding can be minimized with attention to the mating system. Strategies are suggested for maintaining and increasing the genetic diversity in the world's red raspberry breeding populations.

This study focuses on four raspberry (Rubus idaeus) genotypes from two different genetic backgrounds: cvs Glen Prosen and Glen Clova, bred at the Scottish Crop Research Institute (SCRI) and genotypes bred at Horticulture Research International (HRI), East Malling (EM), EM 4997 and EM 5007. The ripe fruit of each genotype pair were characterised subjectively by raspberry breeders as relatively firm or soft, respectively. Different stages of fruit development from each genotype were used to quantify fruit firmness, rates of ethylene evolution and ripening rate. Penetrometry data confirmed suspected firmness differences. Firmness correlated with rates of ethylene evolution. Rates of ethylene production also correlated with receptacle size. Storage of green fruits in 20 μl l−1 ethylene reduced fruit firmness, enhanced respiration rate and colour (anthocyanin) development and stimulated the development of cell wall hydrolase activities. However, during natural ripening in the field, fruit respiration rate declined, which indicates a non‐climacteric ripening pattern. In drupelets, the activities of polygalacturonase (PG), pectin methylesterase (PME), Cx‐cellulase (Cx) and β‐galactosidase (β‐gal.) increased substantially as ripening progressed. More detailed studies with ripe fruit of cv. Glen Clova indicated major isoforms of PG at pIs 3.3, 8.6 and 10.1; of PME at pIs 7.2, 8.5, 8.7, 8.8; of Cx at pI 2.4; and of β‐gal. at pIs 6.3 and 6.7.

Various media, sources of explant and Rubus genotypes of diverse origin were assessed for their ability to regenerate whole plants in vitro. Regenerants were produced from leaf discs and from both peeled and unpeeled internodal stem segments but not from epidermal peelings. Hormone type and concentration, amount of sucrose, absence of activated charcoal, presence of light and for leaf discs their orientation with adaxial surface uppermost were factors crucial for plantlet regeneration, and genotypes differed considerably in their capacity to regenerate.