First Report of Nothophoma quercina Causing Trunk Canker on Crabapple (Malus micromalus) in China

Abstract

HomePlant DiseaseVol. 102, No. 7First Report of Nothophoma quercina Causing Trunk Canker on Crabapple (Malus micromalus) in China PreviousNext DISEASE NOTES OPENOpen Access licenseFirst Report of Nothophoma quercina Causing Trunk Canker on Crabapple (Malus micromalus) in ChinaM. Liu, W. Zhang, I. S. Manawasinghe, Y. Zhou, Q. K. Xing, X. H. Li, J. Y. Yan, and S. WangM. Liu†Corresponding author: M. Liu; E-mail: E-mail Address: liumeidmw@163.comhttp://orcid.org/0000-0002-6785-8090Search for more papers by this author, W. ZhangSearch for more papers by this author, I. S. ManawasingheSearch for more papers by this author, Y. ZhouSearch for more papers by this author, Q. K. XingSearch for more papers by this author, X. H. LiSearch for more papers by this author, J. Y. YanSearch for more papers by this author, and S. WangSearch for more papers by this authorAffiliationsAuthors and Affiliations M. Liu † W. Zhang I. S. Manawasinghe Y. Zhou Q. K. Xing X. H. Li J. Y. Yan , Institute of Plant and Environment Protection, Beijing Academy of Agriculture and Forestry Sciences, Beijing 100097, China S. Wang , Administrative Office of the Summer Palace, Beijing Municipal Administration Center of Parks, Beijing 100080, China. Published Online:23 May 2018https://doi.org/10.1094/PDIS-11-17-1866-PDNAboutSectionsSupplemental ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat Malus micromalus (crabapple) is an ornamental plant mainly distributed in northern China, where the spring climate is warm and dry (mean temperature 1.0 to 12.0°C). Typical trunk cankers on crabapple were observed at the Summer Palace, Beijing, in March 2017. The symptoms included warts on trunk, cracked periderm around warts, roughed bark with scaled periderm, and cankers often expanded and coalesced during dry weather, affecting the ornamental value of crabapple. Symptomatic tissues from the trunk were cut into small pieces (4 × 4 mm), surface-sterilized in 75% alcohol for 1 min, 1% NaClO for 1 min, and then rinsed three times with sterilized water. The sterilized tissues were cultured on potato dextrose agar (PDA) plates (three pieces of tissue per plate) and incubated at 25°C with a 12-h photoperiod for 7 days. Pure cultures of the suspected pathogen were obtained by hyphal-tip and single spore isolation techniques. The colonies on PDA were greenish olivaceous to olivaceous, with pure white, floccose to wooly aerial mycelium. Fifteen days post incubation, abundant, black, solitary, globose, peroblate to suboblate, and 50 to 175 µm (n = 50) diameter pycnidia were scattered over the medium. Conidia were aseptate, hyaline to brown, oval to obtuse, and 4.5 to 7.0 × 2.5 to 4.0 µm (n = 50). For molecular characterization, two representative isolates based on similar morphology characters were selected and four phylogenetic markers (LSU, ITS, TUB2, and RPB2) were amplified by PCR (Chen et al. 2015). The amplicons were sequenced and deposited in GenBank under accession numbers KY887674, KY887675, KY887672, KY887673, KY887678, KY887679, KY887676, and KY887677. Maximum parsimony and Bayesian inference phylogenetic trees were constructed using PAUP (phylogenetic analysis using parsimony) v. 4.0b10 and MrBayes v. 3.1.2. The isolates JZB380007 and JZB380009 clustered together with ex-type culture of Nothophoma quercina (CBS 633.92) with 100% bootstrap support and 1.00 Bayesian posterior probabilities support. Based on the morphological and molecular data, the isolates were identified as N. quercina (Aveskamp et al. 2010; Chen et al. 2015). To confirm pathogenicity, shoots were surface sterilized and wounds (4 mm diam., 1 mm depth) were made with a cork borer. The mycelial plug from mother colonies was placed on the wound, which was then covered with a Parafilm (BEMIS, U.S.A.). Wounded shoots were inoculated with only PDA plugs as controls. Inoculated shoots were placed under dark and moist conditions (70 to 90% RH) at 25°C. Fourteen days later, wounded shoots produced warts and showed peeling symptoms, but controls remained asymptomatic. The same fungus was reisolated from the inoculated shoots, confirming Koch’s postulates. N. quercina has been reported previously in the U.S.A., Tunisia, and Korea (Chen et al. 2013; Taieb et al. 2014; Yun et al. 2016). To our knowledge, this is the first report of N. quercina causing trunk canker in China. Therefore, our report would be useful for its management.