First Report of Brown Rot Caused by Phytophthora nicotianae on Navel Orange Fruit in China

HomePlant DiseaseVol. 107, No. 4First Report of Brown Rot Caused by Phytophthora nicotianae on Navel Orange Fruit in China PreviousNext DISEASE NOTE OPENOpen Access licenseFirst Report of Brown Rot Caused by Phytophthora nicotianae on Navel Orange Fruit in ChinaYusen Xiao, Song Luo, Mengting Guo, Shichang Ai, Guanghua Huo, and Chaoyu CuiYusen Xiaohttps://orcid.org/0000-0002-7771-6248Jiangxi Key Laboratory for Conservation and Utilization of Fungal Resources, Jiangxi Agricultural University, Nanchang 330045, Jiangxi, ChinaSearch for more papers by this author, Song LuoCollege of Bioscience and Bioengineering, Jiangxi Agricultural University, Nanchang 330045, Jiangxi, ChinaSearch for more papers by this author, Mengting GuoCollege of Bioscience and Bioengineering, Jiangxi Agricultural University, Nanchang 330045, Jiangxi, ChinaSearch for more papers by this author, Shichang AiCollege of Bioscience and Bioengineering, Jiangxi Agricultural University, Nanchang 330045, Jiangxi, ChinaSearch for more papers by this author, Guanghua Huo†Corresponding authors: G. Huo; E-mail Address: [email protected], and C. Cui; E-mail Address: [email protected]Jiangxi Key Laboratory for Conservation and Utilization of Fungal Resources, Jiangxi Agricultural University, Nanchang 330045, Jiangxi, ChinaSearch for more papers by this author, and Chaoyu Cui†Corresponding authors: G. Huo; E-mail Address: [email protected], and C. Cui; E-mail Address: [email protected]https://orcid.org/0000-0002-5535-0425Jiangxi Key Laboratory for Conservation and Utilization of Fungal Resources, Jiangxi Agricultural University, Nanchang 330045, Jiangxi, ChinaCollege of Bioscience and Bioengineering, Jiangxi Agricultural University, Nanchang 330045, Jiangxi, ChinaSearch for more papers by this authorAffiliationsAuthors and Affiliations Yusen Xiao1 Song Luo2 Mengting Guo2 Shichang Ai2 Guanghua Huo1 † Chaoyu Cui1 2 † 1Jiangxi Key Laboratory for Conservation and Utilization of Fungal Resources, Jiangxi Agricultural University, Nanchang 330045, Jiangxi, China 2College of Bioscience and Bioengineering, Jiangxi Agricultural University, Nanchang 330045, Jiangxi, China Published Online:27 Mar 2023https://doi.org/10.1094/PDIS-05-22-1066-PDNAboutSectionsView articlePDFSupplemental ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat View articleNavel orange (Citrus sinensis Osbeck cv. Newhall) is widely planted in southern China. From September to November 2021, severe outbreaks of Phytophthora brown rot were observed on navel orange fruit in three local orchards in Ganzhou City (28.80°N, 115.53°E), Jiangxi Province, China, with a disease incidence of 25 to 35%. Symptomatic fruit was mostly observed 1 m from the ground. Initial symptoms on infected fruit were circular, pale-brown to brown, water-soaked, slightly sunken lesions, covered with sparse white mycelia-like growth. As the disease progressed, the lesions turned dark brown and enlarged on the fruit surface. Three to four infected fruits were randomly collected from each orchard, placed in transparent plastic bags, and immediately brought to the laboratory for isolation. Infected fruits were surface disinfested with 70% ethanol for 60 s and rinsed three times with sterile water. Symptomatic tissues from the margin between necrotic and healthy tissues were cut into 5 × 5 mm pieces, placed onto potato dextrose agar, and incubated at 28°C for 5 days. Nine isolates were obtained. Colonies of three isolates (JFRL 03-16, 03-18, 03-19) in 10-day-old 20% V8 juice agar consisted of abundant, white, cottony aerial mycelia. Hyphal swellings and coenocytic mycelium were observed. Sporangia were ovoid, ellipsoid to spherical, papillate, and 17.2 to 60.1 × 15.8 to 48.6 μm (x¯ = 46.2 ± 5.5 × 32.4 ± 4.8 μm, n = 50). Chlamydospores were spherical, suborbicular, and 17.8 to 45.9 μm in diameter (x¯ = 30.5 ± 3.5 μm, n = 50). Oospores were not observed in pure cultures. These morphological characteristics were consistent with those of P. nicotianae (LaMondia et al. 2014). Genomic DNA was extracted from a representative isolate, JFRL 03-18, using the NuClean Plant Genomic DNA kit (CWBIO, China). The internal transcribed spacer (ITS) region, ras-related protein ypt1 (YPT), and β-tubulin (TUB) gene were amplified by PCR using primers ITS1/ITS4 (White et al. 1990), Yph1F/Yph2R (Schena et al. 2008), and TUBUF2/TUBUR1 (Kroon et al. 2004), respectively. All sequences were deposited in GenBank (ON231777 for ITS, ON246910 for YPT, and ON246908 for TUB). A BLASTn homology search for these nucleotide sequences showed 100% identity to the ITS (MH341621), YPT (MK058408), and TUB (MH760160) sequences of P. nicotianae. Sequences of 12 Phytophthora species and Pythium ostracodes were downloaded from GenBank. The phylogenetic tree of combined ITS, YPT, and TUB sequences showed that the isolate JFRL 03-18 clustered with P. nicotianae. To complete Koch’s postulates, zoospore suspensions were prepared from the cultures grown on 10-day-old V8 juice agar of isolates (JFRL 03-16, 03-18, 03-19). Pathogenicity tests were performed on healthy and surface-disinfested navel orange fruit. Nine fruits were gently wounded with a needle, inoculated with a 10-μl zoospore suspension (104 zoospores/ml) of three isolates separately, and three fruit treated with sterilized water as controls. All fruit were incubated at 25°C with 80% relative humidity and the test was repeated three times. After 7 days of incubation, the fruit inoculated with P. nicotianae showed similar brown rot symptoms and the control fruit remained symptomless. The pathogen was reisolated from all inoculated fruits and confirmed as P. nicotianae by morphological and molecular analysis. P. nicotianae was previously reported on Hamlin sweet orange (Citrus sinensis (L.) Osbeck) fruit causing Phytophthora brown rot in Florida (Graham and Timmer 1995; Hao et al. 2018). To our knowledge, this is the first report of P. nicotianae causing Phytophthora brown rot of navel orange fruit in China. Based on the severity of this disease, local growers should develop and implement integrated disease management strategies for control.The author(s) declare no conflict of interest.References:Graham, J. H., and Timmer, L. W. 1995. Citrus Ind. 76:38. Google ScholarHao, W., et al. 2018. Phytopathology 108:384. https://doi.org/10.1094/PHYTO-09-17-0315-R Link, ISI, Google ScholarKroon, L. P. N. M., et al. 2004. Fungal Genet. Biol. 41:766. https://doi.org/10.1016/j.fgb.2004.03.007 Crossref, ISI, Google ScholarLaMondia, J. A., et al. 2014. Plant Dis. 98:1278. https://doi.org/10.1094/pdis-03-14-0297-pdn Link, ISI, Google ScholarSchena, L., et al. 2008. Plant Pathol. 57:64. https://doi.org/10.1111/j.1365-3059.2007.01689.x ISI, Google ScholarWhite, T. J., et al. 1990. Page 315 in: PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, CA. Crossref, Google ScholarFunding: This work was supported by the Natural Science Foundation of Jiangxi Province (20171ACB20014); Youth Fund of Jiangxi Provincial Department of Education (GJJ190225).The author(s) declare no conflict of interest.DetailsFiguresLiterature CitedRelated Vol. 107, No. 4 April 2023SubscribeISSN:0191-2917e-ISSN:1943-7692 Download Metrics Article History Issue Date: 27 Apr 2023Published: 27 Mar 2023First Look: 23 Sep 2022Accepted: 21 Sep 2022 Page: 1245 Information© 2023 The American Phytopathological SocietyFundingNatural Science Foundation of Jiangxi ProvinceGrant/Award Number: 20171ACB20014Youth Fund of Jiangxi Provincial Department of EducationGrant/Award Number: GJJ190225KeywordsChinanavel orangePhytophthora brown rotPhytophthora nicotianaeThe author(s) declare no conflict of interest.PDF download