Wang Chih-Wei, Yu Yu-Hsiang, Wu Chun-Yao, Feng Ru-Ying, Tandon Kshitij, Chen Ying-Lien, Tang Sen-Lin
Taitung District Agricultural Research and Extension Station, Council of Agriculture, Executive Yuan, Taitung, Taiwan.
Biodiversity Research Center, Academia Sinica, Taipei, Taiwan.
Front Microbiol. 2021 Nov 1;12:756100. doi: 10.3389/fmicb.2021.756100. eCollection 2021.
Wilt disease of roselle ( L.) is common in Taiwan; however, the causative agent remains unknown. The stems of wilted roselle are browned, slightly constricted, and covered by white aerial hyphae, suggesting that potential pathogens may originate from soil. To identify the potential pathogens, we conducted a rhizosphere microbiota survey in phenotypically healthy and diseased plants through fungal internal transcribed spacer (ITS) and bacterial 16S rRNA amplicon sequencing for uncovering the microbial compositions in the roselle rhizosphere. The fungal family Nectriaceae exhibited significantly higher abundance in diseased rhizospheres than in healthy rhizospheres, and this bacterial community was more specific to geography (i.e., plot-dependent) than to rhizosphere disease status. However, a few bacterial groups such as were associated with the healthy rhizosphere. species were the most dominant species of Nectriaceae in the survey and became the main target for potential pathogen isolation. We successfully isolated 119 strains from diseased plants in roselle fields. Koch's postulates were used to evaluate the pathogenicity of these strains; our results indicated that K1 (FsK1) can cause wilting and a rotted pith in roselles, which was consistent with observations in the fields. This is the first demonstration that can cause roselle wilt in Taiwan. Furthermore, these newly isolated strains are the most dominant operational taxonomic units detected in ITS amplicon sequencing in diseased rhizospheres, which serves as further evidence that is the main pathogen causing the roselle wilt disease. Administration of SOI-3374, a strain isolated from a healthy roselle rhizosphere, caused considerable anti-FsK1 activity, and it can serve as a potential biocontrol agent against roselle wilt disease.
玫瑰茄（Hibiscus sabdariffa L.）的枯萎病在台湾很常见；然而，病原体仍不明确。枯萎的玫瑰茄茎干呈褐色，略有缢缩，并覆盖着白色气生菌丝，这表明潜在病原体可能源自土壤。为了鉴定潜在病原体，我们通过真菌内转录间隔区（ITS）和细菌16S rRNA扩增子测序，对表型健康和患病的玫瑰茄植株进行了根际微生物群调查，以揭示玫瑰茄根际的微生物组成。真菌丛赤壳科在患病根际的丰度显著高于健康根际，并且该细菌群落对地理因素（即地块依赖性）的特异性高于对根际疾病状态的特异性。然而，一些细菌类群，如 ，与健康根际相关。 在调查中是丛赤壳科最主要的物种，成为潜在病原体分离的主要目标。我们成功地从玫瑰茄田的患病植株中分离出119株菌株。采用柯赫氏法则评估这些菌株的致病性；我们的结果表明， K1（FsK1）可导致玫瑰茄枯萎和髓部腐烂，这与田间观察结果一致。这是首次证明 在台湾可引起玫瑰茄枯萎病。此外，这些新分离的菌株是在患病根际的ITS扩增子测序中检测到的最主要的可操作分类单元，这进一步证明 是导致玫瑰茄枯萎病的主要病原体。从健康玫瑰茄根际分离出的菌株SOI-3374具有显著的抗FsK1活性，可作为防治玫瑰茄枯萎病的潜在生物防治剂。
