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First Report of Botrytis cinerea Causing Fruit Rot of Pyrus sinkiangensis in China

Fragrant pear, Pyrus sinkiangensis Yu, is widely cultured in northern China, and is typically sweeter and of higher economic value than other pears. (2,3). In early October 2012, a fruit rot affecting approximately 30% of 300 kg of P. sinkiangersis produced in Korla orchards of Xinjiang was observed in a market of Zhengzhou, Henan Province, China. Early symptoms appeared as small, round, pale yellow-brown lesions on the fruit, which expanded from 10 to 20 mm diameter in 7 days. Later, affected fruit completely rotted and were covered with grey-white mycelium after 20 days. On the surface of mycelium, branched, septate conidiophores (2.0 mm tall and 13 to 15 μm thick) were produced. These were melanized at the base and hyaline near the apex. Conidia were hyaline, aseptate, ellipsoidal to obovoid, with a slightly protuberant hilum and ranged from 7 to 13.5 × 5.5 to 8.5 μm. One isolate of the pathogen (zm120286) was made by dispersing conidia on the potato dextrose agar (PDA) medium, directly removed from the sporulating tissue with thin needle. The colony was gray to white and produced blackish sclerotia at the edge of the colonies, which was 3.0 to 4.0 × 2.0 to 3.0 mm after 2 weeks of incubation at 22°C. The pathogen was identified as Botrytis cinerea Pers.:Fr on the basis of the morphology and ITS sequencing of rDNA (1,4). The sequence (GenBank Accession No. KF010847) was 100% identical to the sequences of two Botryotinia fuckeliana (anamorph: Botrytis cinerea) (e.g., GenBank Accession Nos. KC683713, HM849615). Koch's postulates were performed by placing a 5 mm diameter mycelia plug removed from the periphery of a 7-day-old colony of zm120286 on 10 surface-sterilized fresh fragrant pears collected from Korla orchards. An equal number of fresh fragrant pears were inoculated with 5 mm diameter plugs of PDA medium to serve as controls. All fragrant pears were incubated in clear plastic boxes with a dish of sterile distilled water at 25°C under ambient light. Symptoms identical to those described in the outbreak above were observed after 3 days. From each of the symptomatic pears, B. cinerea was recovered, whereas controls remained symptom-free. To our knowledge, this is the first outbreak of B. cinerea on P. sinkiangersis in China, which may necessitate the development of pre-harvest management practices.

References: (1) M. B. Ellis. Dematiaceous Hyphomycetes. Commonwealth Mycological Institute, Kew, England, 1971. (2) X.W. Li et al. Chinese Agricultural Science Bulletin, 26(15):100-102, 2010. (3) T. Yu and K. Kuan. Acta Phytotaxon. Sin. 8: 202, 1963. (4) Z. Y. Zhang. Flora Fungorum Sinicorum. Vol. 26. Botrytis, Ramularia. Science Press, Beijing, 2006.