First Report of <i>Boeremia exigua</i> var. <i>exigua</i> Causing Branch Blight on Walnut in China

HomePlant DiseaseVol. 105, No. 10First Report of Boeremia exigua var. Causing Branch Blight on Walnut in China PreviousNext DISEASE NOTE OPENOpen Access licenseFirst ChinaFengfeng Cai, Chengde Yang, Ting Ma, Mengjun Jin, and Lingxiao CuiFengfeng Caihttps://orcid.org/0000-0003-4891-5843College Plant Protection, Gansu Agricultural University, Lanzhou 730070, ChinaBiocontrol Engineering Laboratory Crop Diseases Pests Province, ChinaSearch for more papers by this author, Yang†Corresponding author: C. D. Yang; E-mail Address: [email protected]://orcid.org/0000-0003-4942-8959College Mahttps://orcid.org/0000-0003-3312-6753College Jinhttps://orcid.org/0000-0001-6485-1734College Cuihttps://orcid.org/0000-0002-8460-6493College author AffiliationsAuthors Affiliations Fengfeng Cai1 2 Yang1 † Ma1 Jin1 Cui1 1College 2Biocontrol Published Online:1 Nov 2021https://doi.org/10.1094/PDIS-02-21-0382-PDNAboutSectionsView articlePDFPDF Plus ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat View articleWalnut (Juglans sinensis L.) is an economically important tree. Its fruit rich omega-3 essential fatty acids, which are valuable nutritionally (Cheon et al. 2013). In March 2019, severe branch blight walnuts (cv. Qingxiang) was observed two fields Ganquan Town, (N 33°56′, E105°44′). The incidence about 3% among 10,000 walnuts. Disease symptoms included fusiform or oval black lesions that gradually expanded the branches, dieback reddish brown dead bark with lots small spots (pycnidia), defoliation. To isolate pathogen, 30 diseased tissues collected from different trees were disinfected 0.1% HgCl solution 1 min, rinsed sterilized water three times, placed potato dextrose agar (PDA) at 25°C dark. About 3 days later, four fungal isolates (3-3, 3-6, 3-9, H3) similar morphological characteristics obtained. Their colonies, regular margins oatmeal agar, 6.1 6.8-cm diameter after 7 days, loose, greenish olivaceous gray, velvety, floccose woolly. conidia (n = 60) 4.77 8.84 μm long (mean 6.88 μm; SD ± 0.91 μm) × 1.71 3.89 wide 2.81 0.53 μm), cylindrical, ellipsoidal oblong, hyaline, aseptate. Pycnidia 25) 76.66 132.86 102.93 12.15 variable shape size, mostly globose subglobose. These (Boerema 2004). Pathogenicity tests performed times five healthy 2- 3-year-old Qingxiang). Plants wounded insect needle (no. 6) inoculated a 5-mm mycelium block grown PDA medium as control kept moist climatic cabinet (>85% RH, 25°C). After occurred branches expanded, but asymptomatic. Original reisolated these shoots. Genomic DNA extracted, internal transcribed spacer (ITS), β-tubulin (tub2) gene, RNA polymerase II second largest subunit (rpb2) gene amplified sequenced using primers ITS1/ITS4, Btub2Fd/Btub4Rd, RPB2-5F2/fRPB2-7CR (Chen 2015; White 1990; Woudenberg 2009), respectively. Sequences deposited GenBank (accession nos.: ITS, MT154621, MT154622, MT154623, MT154624; tub2, MT223481, MT223482, MT223483, MT223484; rpb2, MW448152, MW448153, MW459982, MW459983) compared available sequences NCBI. Results showed ITS had 100% sequence identity spp., tub2 rpb2 B. (GenBank accession nos. MN983734 MN983315) linicola MN983785 MT920619). According host specificity Verhoeven 1976), 106 conidia/ml spore suspension sterile stem base 2-month-old flax seedlings, 25°C) moisturizing repeated times. weeks, all plants still asymptomatic, indicating not linicola. Therefore, they identified based characteristics, molecular analysis, pathogenicity tests. our knowledge, first report causing walnut worldwide, will provide further guidance prevention blight.The author(s) declare no conflict interest.References:Boerema, G. H., Verhoeven, A. 1976. Neth. J. Pathol. 82:193. https://doi.org/10.1007/BF03041376 Crossref, Google ScholarBoerema, 2004. Phoma Identification Manual. CAB International, Wallingford, U.K. ScholarChen, Q., 2015. Stud. Mycol. 82:137. https://doi.org/10.1016/j.simyco.2015.10.003 ISI, ScholarCheon, W., 2013. Dis. 97:1114. Link, ScholarWhite, T. J., 1990. Page 315 in: PCR Protocols: A Guide Methods Applications. Academic Press, San Diego, CA. ScholarWoudenberg, H. C., 2009. Persoonia 22:56. https://doi.org/10.3767/003158509X427808 ScholarThe interest.DetailsFiguresLiterature CitedRelated Vol. 10 October 2021SubscribeISSN:0191-2917e-ISSN:1943-7692 DownloadCaptionPycnidia Leptosphaeria biglobosa formed necrotic tissue blighted leaf petiole Brassica rapa subsp. pekinensis (C. Yu al.). Photo credit: Yu. Panicle blast rice site sub-Saharan Africa (S. K. Mutiga V. Were. Symptoms bud soft rot agave caused Pantoea dispersa (F. Palemón-Alberto S. Ortega-Acosta. Metrics Downloaded 517 Article History Issue Date: 28 Dec 2021Published: 2021First Look: Apr 2021Accepted: 25 2021 Page: 3291 Information© American Phytopathological SocietyKeywordsfungitreestree nutspathogen detectionThe interest.