Pathogenic Penicillium spp. on Apple and Pear.

Numerous Penicillium spp. have been associated with postharvest fruit spoilage. This study investigates pathogenicity and aggressiveness of selected Penicillium spp. previously isolated from South African and European Union fruit export chains. Penicillium expansum was the most aggressive and P. crustosum the second most aggressive on all apple cultivars ('Royal Gala', 'Granny Smith', 'Golden Delicious', 'Topred', and 'Cripps Pink') and two pear cultivars ('Packham's Triumph' and 'Forelle') tested. P. digitatum was the most aggressive on 'Beurre Bosc', 'Beurre Hardy', and 'Sempre' ('Rosemarie') pear cultivars and the third most aggressive on Granny Smith and Cripps Pink apple cultivars. To our knowledge, this is the first report where P. digitatum has been described as aggressive on certain pome fruit cultivars. These pear cultivars are also the most commonly associated with decay on the export markets, resulting in considerable end-market losses. P. brevicompactum was detected as pathogenic on pear but was not further evaluated in the study. P. solitum covered a broader cultivar range, expressed higher disease incidence, and was more aggressive (larger lesions) on pear cultivars than on apple cultivars. This study provides new information on host specificity and the importance of pathogenic Penicillium spp. isolated from various environments in the shipping and marketing channels.