Breeding of resistant strawberry cultivars for organic fruit production - Preliminary results with botrytis cinerea

Resistant strawberry cultivars represent an important prerequisite for organic cultivation systems to overcome high yield losses caused by fungal and bacterial diseases. To evaluate differences in susceptibility towards the fungal pathogen Botrytis cinerea Pers. (teleomorph Botryotinia fuckeliana) fruits from 13 different strawberry cultivars were artificially infected with field isolates from this pathogen. For infection, field isolates from grey mould-infected strawberries were taken and verified in a molecular approach using a PCR method. A resistance test was established by infecting fruits under standardized conditions using a defined inoculation procedure. First symptoms of grey mould occurred 1-3 dpi (days post inoculation) at 20°C in the climate cabinet. Different degrees of susceptibility and resistance became apparent 6 dpi and were evaluated with a scale from 0 = no fruit rot to 4 = full fruit rot. Susceptible cultivars like 'Senga Sengana' reached a score of 4 at 6 dpi whereas 'Florence' showed the lowest symptoms of fruit rot with a score of 0.7 and can be considered as relatively resistant towards grey mould disease. A comprehensive genetic evaluation of numerous strawberry cultivars, breeding clones and wild types will lead to the identification of resistant genotypes.