First Report of Tobacco Fusarium Root Rot Caused by Fusarium redolens in China

Abstract

HomePlant DiseaseVol. 107, No. 2First Report of Tobacco Fusarium Root Rot Caused by Fusarium redolens in China PreviousNext DISEASE NOTE OPENOpen Access licenseFirst Report of Tobacco Fusarium Root Rot Caused by Fusarium redolens in ChinaX. T. Gai, Y. X. Hu, K. Dai, J. M. Wang, N. Jiang, C. H. Lu, and Z. Y. XiaX. T. Gai†Corresponding author: X. T. Gai; E-mail Address: [email protected]https://orcid.org/0000-0002-0923-6728Yunnan Academy of Tobacco Agricultural Sciences, Kunming 650031, ChinaSearch for more papers by this author, Y. X. HuDali Tobacco Company of Yunnan, Dali 671000, ChinaSearch for more papers by this author, K. DaiYuxi Tobacco Company of Yunnan, Yuxi 653100, ChinaSearch for more papers by this author, J. M. WangLincang Tobacco Company of Yunnan, Lincang 677300, ChinaSearch for more papers by this author, N. JiangYunnan Academy of Tobacco Agricultural Sciences, Kunming 650031, ChinaSearch for more papers by this author, C. H. Luhttps://orcid.org/0000-0002-9165-5138Yunnan Academy of Tobacco Agricultural Sciences, Kunming 650031, ChinaSearch for more papers by this author, and Z. Y. XiaYunnan Academy of Tobacco Agricultural Sciences, Kunming 650031, ChinaSearch for more papers by this authorAffiliationsAuthors and Affiliations X. T. Gai1 † Y. X. Hu2 K. Dai3 J. M. Wang4 N. Jiang1 C. H. Lu1 Z. Y. Xia1 1Yunnan Academy of Tobacco Agricultural Sciences, Kunming 650031, China 2Dali Tobacco Company of Yunnan, Dali 671000, China 3Yuxi Tobacco Company of Yunnan, Yuxi 653100, China 4Lincang Tobacco Company of Yunnan, Lincang 677300, China Published Online:1 Feb 2023https://doi.org/10.1094/PDIS-02-22-0374-PDNAboutSectionsPDF ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat In July 2021, a disease with an average incidence of 5% on tobacco plants (Nicotiana tabacum L.) was observed in Yunnan province. Initial symptoms were wilting on lower leaves and poor plant growth. With the development of infection, the lower leaves became chlorotic, and some roots changed color to brown. In high soil moisture, symptoms of rot expanded in the roots, whole plants became wilted and stunted, and in more serious cases, some plants ultimately died. To isolate the causal agent, nine symptomatic roots (cultivar Honghuadajinyuan) were collected from a 3-acre field in Kunming (24.68° N, 103.26° E). The lesion and healthy tissue were cut, surface sterilized (75% ethanol for 30 s, followed by 2% wt/vol of NaOCl for 1 min), washed with sterile distilled water three times, then dried on sterilized filter paper, and plated on potato dextrose agar (PDA) for 3 days at 25°C. Nine isolates were obtained from nine samples. Each isolate was obtained from a single spore and examined for morphological and molecular analyses. The colony on PDA formed dense white aerial mycelium, which was observed after 5 days. Macroconidia were falcate, slightly curved, three to five septa, and measured 17.5 to 38.3 × 2.2 to 3.3 μm (n = 50). Microconidia were oval, zero to one septa, and 5.1 to 11.6 × 1.8 to 3.4 μm (n = 50). Chlamydospores were absent. The colony morphology and conidial characteristics were similar to those of Fusarium spp. (Leslie and Summerell 2006). For molecular analyses, the internal transcribed spacer (ITS) region of rDNA, translation elongation factor 1ɑ (EF-1α), and the RNA polymerase II beta subunit (RPB2) genes were amplified and sequenced using primers ITS1/ITS4 (White et al. 1990), EF-1H/EF-2T (Geiser et al. 2004), and RPB2-5F/RPB2-7cR (Reeb et al. 2004), respectively. The sequences of the isolate 21SL97 showed that BLAST analysis of the 559-bp ITS sequence (OM666548) resulted in 100% identity with Fusarium redolens strain JH11-2 (MT563396), and the 730-bp EF-1α sequence (OM622423) showed 99% identity with F. redolens strain CBS:743.97 (MT010987), while the RPB2 gene sequences had 100% identity to F. redolens strain NA_FRA03. Among the other eight isolates, six were identified as F. oxysporum and two were identified as F. solani. Pathogenicity tests were conducted to fulfill Koch’s postulates. Ten six-leaf-stage tobacco seedlings cultivar Yunyan 87 were used. A conidial suspension (105 spores/ml) was poured over the roots of tobacco seedlings. Three seedlings were treated with sterile water that served as a control. All 10 seedlings were maintained at 25°C and 70% relative humidity. After 5 days, the lower leaves showed symptoms of wilting and the roots showed discoloration on all inoculated seedlings, whereas the control seedlings did not develop symptoms. The fungus reisolated from the inoculated seedlings was identical to F. redolens using the EF-1α gene sequence. Fusarium root rot on tobacco was reportedly caused by F. oxysporium f. sp. nicotianae in China. As far as we know, F. redolens was identified in tobacco in Malaysia (Salleh and Strange 1988). In recent years, F. redolens was reported in different crops in China (Cao et al. 2018; Fan et al. 2021; Guan et al. 2014; Tang et al. 2021; Wang et al. 2019). However, to the best of our knowledge, this is the first report of F. redolens causing root rot on tobacco in China. Identification of F. redolens as a root rot agent might provide important insight for disease management practices on tobacco caused by Fusarium species.The author(s) declare no conflict of interest.