Abstract

Mature fruits from red raspberry (Rubus idaeus) genotypes in the greenhouse or field were subjected to various treatments to determine the role of conidia of B. cinerea in the infection of drupelets at the ripe fruit stage and in postharvest grey mould. Natural mould development at c. 100% RH in untreated fruits was compared with that in fruits in which drupelets had been either wounded with a fine needle and inoculated by dusting with conidia, inoculated without prior wounding, or wounded alone. The results indicated little difference between the effects of either wounding or inoculation alone on shelf life, but when these treatments were combined shelf-life was markedly reduced. Low-temp. SEM showed that conidia germinated only in the juice around wounds. At 20C conidia took about 3 days to germinate and induce a visible mould. The background inoculum present as mycelium in senescent, attached styles masked many infections that might have arisen from superficial conidia after harvest. Losses were reduced from 54 to 31% after 3 days when fruits were stored during the first 24 h at 2C, rather than at 20C throughout; only 7% became mouldy when incubated constantly at 10C. The results are discussed in the context of 'cold chain marketing' and strategies for breeding for resistance to postharvest grey mould.