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First Report of Neofusicoccum luteum Causing Stem-End Rot Disease on Avocado Fruits in Chile

2020; American Phytopathological Society; Volume: 104; Issue: 7 Linguagem: Inglês

10.1094/pdis-11-19-2299-pdn

1943-7692

L. Tapia, Alejandra Larach, Natalia Riquelme, J. Guajardo, Ximena Besoaín,

Plant-Microbe Interactions and Immunity

HomePlant DiseaseVol. 104, No. 7First Report of Neofusicoccum luteum Causing Stem-End Rot Disease on Avocado Fruits in Chile PreviousNext DISEASE NOTES OPENOpen Access licenseFirst Report of Neofusicoccum luteum Causing Stem-End Rot Disease on Avocado Fruits in ChileL. Tapia, A. Larach, N. Riquelme, J. Guajardo, and X. BesoainL. TapiaEscuela de Agronomía, Facultad de Ciencias Agronómicas y de los Alimentos, Pontificia Universidad Católica de Valparaíso, Chile, A. LarachEscuela de Agronomía, Facultad de Ciencias Agronómicas y de los Alimentos, Pontificia Universidad Católica de Valparaíso, Chile, N. RiquelmeEscuela de Agronomía, Facultad de Ciencias Agronómicas y de los Alimentos, Pontificia Universidad Católica de Valparaíso, Chile, J. GuajardoEscuela de Agronomía, Facultad de Ciencias Agronómicas y de los Alimentos, Pontificia Universidad Católica de Valparaíso, Chile, and X. Besoain†Corresponding author: X. Besoain; E-mail Address: ximena.besoain@pucv.clhttp://orcid.org/0000-0002-4861-7961Escuela de Agronomía, Facultad de Ciencias Agronómicas y de los Alimentos, Pontificia Universidad Católica de Valparaíso, ChileAffiliationsAuthors and Affiliations L. Tapia A. Larach N. Riquelme J. Guajardo X. Besoain † Escuela de Agronomía, Facultad de Ciencias Agronómicas y de los Alimentos, Pontificia Universidad Católica de Valparaíso, Chile Published Online:7 May 2020https://doi.org/10.1094/PDIS-11-19-2299-PDNAboutSectionsSupplemental ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat Chile is the world's third largest exporter of avocado (Persea americana Mill.), after Mexico and Peru. Avocados are grown on about 29,000 ha (http://www.odepa.gob.cl/, 2019) and are mainly exported to the United States and Europe. In January 2017, avocado fruits (cv. Hass) showed symptoms of light brown spherical lesions in the peel and pulp, peduncle base lesions (3 to 5 cm width), and necrotic veins. Symptomatic fruits were obtained from trees located in a commercial orchard from the commune of Santo Domingo, Valparaíso Region, Chile (33°43′26″ S, 71°46′25″ W). The estimated disease incidence was 40%. From six symptomatic fruits, samples of peel and flesh tissue were taken from the advance zone of the lesions, disinfected (1% hypochlorite, 30 s), washed three times with sterile distilled water, dried, and transferred to plates with acidified potato dextrose agar medium. The plates were incubated in the dark for 5 to 7 days at 25°C. From these tissues, a white mycelium developed, reaching the edge of the Petri dish (90 mm) in 2 days, which turned gray in subsequent days, and a pale yellow pigment was observed during the first 7 days. After 14 days of exposure of the plates to UV-A light (320 nm), pycnidia were produced. The conidia obtained from pycnidia were hyaline, smooth surface, ellipsoidal with a truncated base, usually unicellular and fusiform, and an average length of 19.25 µm (17 to 21 µm) and an average width of 6 µm (5 to 7 µm), considering 20 conidia per isolate. Isolates (palb2017, palb2018, and palb2022) were preliminarily identified as Neofusicoccum sp. according to the key of Phillips et al. (2013). For the molecular identification, DNA from the three isolates was extracted from the mycelium of a monosporic culture of each isolate. The internal transcribed spacer region (ITS) and β-tubulin (β-tub) region were amplified by polymerase chain reaction (PCR) using the primers ITS4/ITS5 and Bt2a_F/Bt2b_R, respectively. The PCR products were sequenced and identified using BLASTN (NCBI). Isolate palb2017 had 99% similarity to Neofusicoccum luteum for ITS (KY711214.1, U.S.A.) and β-tub (KX464956.1, Netherlands); isolate palb2018 had 100% similarity to N. luteum for ITS (KY711214.1, U.S.A.) and β-tub (KX464956.1, Netherlands); and isolate palb2022 had 99 and 100% similarity to N. luteum for ITS (KY711214.1, U.S.A.) and β-tub (KX464956.1, Netherlands), respectively. The sequences of the Chilean isolates were deposited in GenBank with accession numbers MG978120 (ITS) and MH006966 (β-tub) for palb2017, MG978121 (ITS) and MH006967 (β-tub) for palb2018, and MG978122 (ITS) and MH006968 (β-tub) for palb2022. A pathogenicity test was performed using the three identified isolates (palb2017, palb2018, and palb2022) with avocado fruits cultivar Hass (n = 5 per isolate), which were ripe and green, apparently healthy. The fruits were sterilized (1% hypochlorite, 30 s), washed three times with sterile distilled water (1 min), and inoculated by introducing a piece of agar with mycelium (5 mm) inside the fruit (3 to 4 mm depth) near the peduncular area on a wound caused with a sterile cork borer and then sealed with Parafilm. Negative controls (n = 5) were inoculated with pieces of pure agar. The fruits were incubated in aseptic moist chambers for 1 week at room temperature (25 ± 2°C). Seven days postinoculation, around the point of inoculation, a brown lesion (mean diameter 44 mm) was observed in the skin with soft rot in the pulp and presence of necrotic veins in the peduncular area of the fruit. The control fruits remained asymptomatic. N. luteum was reisolated from the inoculated fruits but not from the mock-inoculated ones, thus confirming Koch's postulates. Stem-end rot disease was previously reported in California caused by N. luteum (Twizeyimana et al. 2013). In Chile, the disease was first reported by Montealegre et al. (2016) caused by N. australe and by Valencia et al. (2019) caused by N. parvum. This is the first report of N. luteum causing stem-end rot disease in avocado in Chile.The author(s) declare no conflict of interest.References:Montealegre, J., et al. 2016. Plant Dis. 100:2532. https://doi.org/10.1094/PDIS-05-16-0738-PDN Link, ISI, Google ScholarPhillips, A. J. L., et al. 2013. Semental. Mycol. 76:51. Crossref, ISI, Google ScholarTwizeyimana, M., et al. 2013. Plant Dis. 97:1580. https://doi.org/10.1094/PDIS-03-13-0230-RE Link, ISI, Google ScholarValencia, A., et al. 2019. Plant Dis. 103:996. https://doi.org/10.1094/PDIS-07-18-1131-RE Link, ISI, Google ScholarThe author(s) declare no conflict of interest.DetailsFiguresLiterature CitedRelated Vol. 104, No. 7 July 2020SubscribeISSN:0191-2917e-ISSN:1943-7692 DownloadCaptionA cucumber plant with a light gray lesion of charcoal rot at the soil line and microsclerotia visible on the stem (D. S. Egel et al.). Photo credit: D. S. Egel. Rot and discolored sepals of persimmon fruit caused by Mucor inaequisporus (S.-Y. Lee and H.-Y. Jung). Photo credit: H.-Y. Jung. Metrics Article History Issue Date: 2 Jul 2020Published: 7 May 2020Accepted: 8 Mar 2020 Pages: 2027-2027 Information© 2020 The American Phytopathological SocietyKeywordsavocadoNeofusicoccum luteumstem-end rotPersea americanaThe author(s) declare no conflict of interest.Cited byFungal Pathogens Associated with Aerial Symptoms of Avocado (Persea americana Mill.) in Tenerife (Canary Islands, Spain) Focused on Species of the Family Botryosphaeriaceae25 February 2023 | Microorganisms, Vol. 11, No. 3Neofusicoccum luteumCABI Compendium, Vol. CABI Compendium