Pear (Pyrus communis L.) is widely grown in Italy, the leading producer in Europe. In summer 2011, a previously unknown rot was observed on fruit of an old cultivar, Spadoncina, in a garden in Torino Province (northern Italy). The decayed area of the fruit was soft, dark brown, slightly sunken, circular, and surrounded by an irregular margin. The internal decayed area appeared rotten and brown and rotted fruit eventually fell. To isolate the causal agent, fruits were soaked in 1% NaOCl for 30 s and fragments (approximately 2 mm) were taken from the margin of the internal diseased tissues, cultured on potato dextrose agar (PDA), and incubated at temperatures between 20 and 28°C under alternating light and darkness. Colonies of the fungus initially appeared whitish, then turned dark gray. After about 30 days of growth, unicellular elliptical hyaline conidia were produced in pycnidia. Conidia measured 16 to 24 × 5 to 7 (average 20.1 × 5.7) μm (n = 50). The morphological characteristics are similar to those of the fungus Botryosphaeria dothidea (Moug.: Fr.) Ces. & De Not. (4). The internal transcribed spacer (ITS) region of rDNA was amplified with the primers ITS1/ITS4 and sequenced. BLAST analysis (1) of the 473-bp segment showed a 100% similarity with the sequence of the epitype of B. dothidea AY236949. The nucleotide sequence has been assigned the GenBank Accession No. JQ418493. Pathogenicity tests were performed by inoculating six pear fruits of the same cultivar (Spadoncina) after surface disinfesting in 1% sodium hypochlorite and wounding. Mycelial disks (8 mm diameter), obtained from 10-day-old PDA cultures of one strain, were placed on wounds. Six control fruits were inoculated with plain PDA. Fruits were incubated at 25 ± 1°C in plastic boxes. The first symptoms developed 3 days after inoculation. After 5 days, the rot was very evident and B. dothidea was consistently reisolated. Noninoculated fruits remained healthy. The pathogenicity test was performed twice. B. dothidea was identified on decayed pears in the United States (2), South Africa, New Zealand, Japan, and Taiwan (3). To our knowledge, this is the first report of the presence of B. dothidea on pear in Italy, as well as in Europe. In Italy, the economic importance of the disease on pear fruit is at present limited, although the pathogen could represent a risk for this crop.
References: (1) S. F. Altschul et al. Nucleic Acids Res., 25:3389, 1997. (2) L. F. Grand. Agr. Res. Serv. Techn. Bull. 240:1, 1985. (3) Y. Ko et al. Plant Prot. Bull. (Taiwan) 35:211, 1993. (4) B. Slippers et al. Mycologia 96:83, 2004.
