Abstract:
Objective Pathogen of the tea leaf spot disease occurred at Duyun was identified and effective fungicides for field control determined.
Method Pathogenic microbes were isolated and purified using the tissue isolation method. Pathogenicity of the isolates was verified according to Koch’s protocol. Positive pathogen was identified according to morphological observation and phylogenetic analysis with concatenated multi-gene sequences including nuclear ribosomal RNA internal transcribed spacer (ITS), translation elongation factor 1-α (TEF1-α), and β-tubulin (TUB2). Susceptibility of the isolate to various germicides was evaluated using the mycelial growth rate method.
Result The pathogen that caused the leaf spot disease on tea plants at Duyun was identified as Botryosphaeria dothidea. It was the first reported case in Guizhou Province. Of various fungicides, the 50% carbendazim wettable powder showed the strongest inhibitory activity against the fungus, with an EC50 of 0.16 mg·L−1. The 40% difenoconazole suspension concentrate and 45% prochloraz emulsion in water had EC50 of 3.84 mg·L−1 and 5.0 mg·L−1, respectively. The biological agents, specifically the 0.5% chitosan aqueous solution and 25% oligosaccharide·ethylicin microemulsion, also exhibited substantial inhibitory activities, with EC50 of 17.68 mg·L−1 and 26.01 mg·L−1, respectively.
Conclusion B. dothidea was identified as the pathogen of the leaf spot disease on tea plants at Duyun. Chemical fungicides, e.g., carbendazim, difenoconazole, and prochloraz, were recommended for controlling severe outbreaks and the bio-fungicides, such as chitosan or oligosaccharide·ethylicin, for mild cases detected at early stages.
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