Identification and characterization of Colletotrichum fructicola causing black spots on young fruits related to bitter rot of pear (Pyrus bretschneideri Rehd.) in China Jingjing Jiang a, b, c , Hongyan Zhai a, b, c , Huannan Li a, b, c , Zhenhua Wang a, b, c, d , Yongsen Chen e , Ni Hong a, b, c , Guoping Wang a, b, c , Gilbert Nchongboh Chofong a, b, c , Wenxing Xu a, b, c, * a State Key Laboratory of Agricultural Microbiology, Wuhan, Hubei 430070, PR China b College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei 430070, PR China c Key Lab of Plant Pathology of Hubei Province, Wuhan, Hubei 430070, PR China d Hubei Entry-exit Inspection and Quarantine Bureau of P.R.C, Wuhan, Hubei 430070, PR China e Guangxi Subtropical Crops Research Institute, Nanning, Guangxi 53002, PR China article info Article history: Received 19 October 2013 Received in revised form 1 January 2014 Accepted 5 January 2014 Keywords: Pathogen identification Etiology Dangshansuli Anthracnose Fruit rot Quiescent infection abstract In recent years, Pyrus bretschneideri Rehd. var. ‘Suli’ has been damaged by a disease characterized by the presence of black spots on young fruit in China, which was always followed by severe bitter rot on matured fruits. The etiology of these symptoms and their relationship with the bitter rot was unknown. A colony was routinely isolated from young and matured ‘Suli’ pear fruits showing black spots and rot symptoms, respectively. This fungal colony was identified as Colletotrichum fructicola based on morphological characteristics and DNA sequence data of 7 regions. C. fructicola was confirmed to be capable of eliciting both black spots and bitter rot symptoms by completion of Koch’s Postulates. The results suggested that the disease characterized by the presence of black spots on young fruits is indeed an early stage of the bitter rot observed on matured fruits of ‘Suli’ pear. Variety resistance analysis indicated an obvious resistance variation possessed by the pear varieties generally cultured in China, with black spots only occurring on some pear varieties. Our results also indicated that wounding can break the quiescent infections, enhance the infectivity of C. fructicola, and lead to more rapid rot of young and matured fruits. These results provided a clear clue that C. fructicola can invade some varieties of P. bretschneideri Rehd. directly without entry via wounds, but subsequently turned into quiescent infection and causing black spots on the fruit surface. The quiescent infection acts as a pathogenic factor responsible for bitter rot of matured fruits. The influence of temperature and pH conditions for growth and colony morphology of C. fructicola were also evaluated. The characterization of C. fructicola causing bitter rot of pear (P. bretschneideri) is expected to provide useful information for controlling this economically important disease. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction ‘Suli’ pear (Pyrus bretschneideri var. ‘Suli’, also known as ‘Dang- shansuli’), cultivated for more than 500 years, is the most impor- tant commercial Asiatic pear variety in the world with a production at over 4 million tons per year (Wu et al., 2013). Considering its significance, it was chosen for whole genome sequencing of pear (Wu et al., 2013). In recent years, ‘Suli’ pears cultivated in Dangshan County, in the Anhui Province of China, have exhibited a severe disease symptom charactrized by black spots on the fruit. These symptoms can be observed during the fruit growing period until the fruit reaches maturity. This disease is commonly known as “black spot disease” in China. It is characterized by the emergence of small black spots of about 1.0 mm in diameter on the surface of young fruits. At the maturation stage, numerous fruits rot, while no obvious sign indicates that black spots develop into fruit rot when the fruit reaches maturity. Severe occurrences of this disease were observed in the areas of Dangcheng, Gedian, Xuanmiao, and Liangli in Dangshan County. In the orchards surveyed in this study, fruit * Corresponding author. State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, Hubei 430070, PR China. Tel.: þ86 15527800168. E-mail addresses: xuwenxing@mail.hzau.edu.cn, xuwenxing@163.com (W. Xu). Contents lists available at ScienceDirect Crop Protection journal homepage: www.elsevier.com/locate/cropro 0261-2194/$ e see front matter Ó 2014 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.cropro.2014.01.003 Crop Protection 58 (2014) 41e48