FIRST REPORT OF PILIDIUM CONCAVUM AS THE CAUSATIVE AGENT OF TAN-BROWN ROT OF PRUNUS DOMESTICA FRUITS

Abstract

In July 2012, an unknown disease of Prunus domestica consisting of yellowish brown lesions (1-2 cm in diameter) of the fruits with the presence of sporodochia was observed in many areas of Mazandaran province (northern Iran). A fungus isolated on potato dextrose agar (PDA), matched morphologically the description of Pilidium concavum (Desm.) Hohn (Rossman et al., 2004). Colonies were light salmon-beige, woolly, zonate, with sparse older mycelium and showed many dark, hemispherical conidiomata. Sporodochia were 273-354×86-121 μm with conidiophores 13.7-47.5 μm in length. Conidia were unicellular, cylindrical to fusiform, hyaline, 4.3-7.5×0.8-1.9 μm (mean 5.6×1.4) in size. The internal transcribed spacer region of rDNA was amplified using primers ITS 1 and ITS 4 and the sequence was submitted to GenBank (accession No. KC614564). A BLASTn search disclosed 99% similarity of this sequence to that of P. concavum (JX047867.1). For pathogenicity tests of the isolated fungus, a spore suspension (1×106 spores per ml) was sprayed on P. domestica fruits wounded by a needle (1 mm in diameter) to a depth of 2 mm. After inoculation, the fruits were covered with plastic bags and incubated for 6 days at 25°C and 90% relative humidity. Lesions like those observed in the field developed on inoculated fruits, from which the fungus was successfully re-isolated. Control fruits sprayed with water remained symptomless. P. concavum has been reported from strawberries fruits and stem (Mass, 1998; Lopes et al., 2010). To our knowledge, this is the first report of P. concavum causing fruit rot of stone fruits worldwide.