Isolation of Acremonium Species Causing Postharvest Decay of Peaches in Spain.

Two Acremonium spp., A. tubakii and A. rutilum, were isolated from rotted peaches (Prunus persica (L.) Batsch 'Miraflores') after ripening at 15 and 20°C, respectively, for 10 days. Fruit harvested in September 1994 in Mula (Murcia) at a firm-ripe stage of maturity were either nontreated or washed with water at 18°C and sorted in a packing line. Sorted fruit were treated with an aqueous dilution of iprodione (Rovral 50% WP Rhône-Poulenc Agrochimie, Paris, France) at 2 g·liter^-1, pH = 7, and 18°C for 5 min. Half of the iprodione-treated fruit were forced-air pre-cooled to reach 0°C at the endosperm in about 12 h. Isolations of fungi were made from subepidermic tissue of decay margins of fruit with potato dextrose agar (PDA). Fungal species were identified after axenic cultures were grown on PDA for 10 days at 30°C. Acremonium spp. were identified based on microscopic morphology of asexual reproduction structures, using taxonomic keys. No other fungi were isolated from fruit decayed by Acremonium spp. A. tubakii decayed 1.7% of the iprodionetreated and pre-cooled fruit ripened at 15 or 20°C and the fruit treated by iprodione without pre-cooling but ripened at 20°C. These fruit were completely decomposed and oozed liquid. Colonies of this species were light colored, with nonramified, nonseptate, and hyaline conidiophores. The one-cell, ovate, and hyaline conidia of the fungus were enclosed in slimy heads. A. tubakii did not cause any brown discoloration of the PDA media. A. rutilum affected 3.2% of the iprodione-treated fruit ripened at 20°C. In contrast to A. tubakii infection, A. rutilum affected only the surface of fruit, which remained dry. Cultures of A. rutilum were white to pink and the conidia were one-celled, ovate, and hyaline, forming a head on the tip of the nonramified conidiophores. Conidia were long, nonseptate, and distinct from the somatic hyphae. Acremonium spp. probably developed on injuries caused by handling and/or treatments, because these rots did not occur on untreated fruit. Rhizopus nigricans, and to a lesser extent other fungi such as Alternaria, Cladosporium, and Penicillium spp., also commonly caused decay of sampled fruit. A. tubakii is a ubiquitous soil fungus reported from various European countries. A. rutilum isolated from diseased apples were pathogenic upon reinoculation (1). Both fungi were not found in the Spanish type culture collection of 1990. Other Acremonium spp. have been identified in melon roots in Spain (2). To the best of our knowledge, this is the first report of Acremonium spp. causing decay of peach in Spain. References: (1) C. Brooks et al. Phytopathology 4:403, 1914. (2) J. García-Jiménez et al. Plant Dis. 78:416, 1994.