Anthracnose of American ginseng is caused by Colletotrichum panacicola. In this study, Bacillus velezensis B313-6, isolated from the rhizosphere soil of American ginseng, was identified based on morphological, physiological, biochemical, 16S rRNA, and the gyrase subunit A protein (gyrA) regions’ analyses. B. velezensis B313-6 showed strong antagonistic activity against C. panacicola with an inhibition rate of 94.4% in dual culture assay, and exhibited broad-spectrum antifungal activity against eight other plant pathogenic fungi (inhibition rates 70–94%). Using single-factor experiments combined with response surface methodology, the fermentation conditions were optimized, increasing the inhibition rate against C. panacicola from 93.9% to 97.4%. In field trials, the B. velezensis B313-6 fermentation broth at a low dose (33.3 mL/m2) provided a control efficacy of 67.6% after the third spray, comparable to a commercial B. subtilis product used as a positive control. The low-dose treatment also significantly promoted American ginseng growth, increasing plant height, root length, shoot fresh weight and root fresh weight by 9.7%, 11.3%, 10.5% and 15.5%, respectively, compared to the treatment of water. These results indicate that B. velezensis B313-6 has great potential as a biocontrol agent against the anthracnose of Panax quinquefolius and also promotes the growth of American ginseng.
Shuang Feng, Yue Shi, Ruijie Liu et al.· Agriculture· 0 citations
Ginseng (Panax ginseng), a traditional and valuable medicinal plant, is severely affected by rusty root rot caused by Ilyonectria robusta. Xylanase is hypothesized to play a key role in the pathogenicity of I. robusta. Through transcriptomic analysis during ginseng infection, the highly expressed xylanase gene IrXyn01 was identified. A PEG-mediated genetic transformation system for I. robusta was established in this study, with optimized protoplast preparation yielding 1.4 × 107 protoplasts/mL and 36% transformation efficiency. IrXyn01 was successfully knocked out by using the CRISPR/Cas9 method. No significant differences in colony morphology, growth rate, sporulation, and spore germination were observed between mutants and the wild-type stain, indicating IrXyn01 is unrelated to vegetative growth. Under salt stress (KCl and NaCl), mutant inhibition reached 37.2% and 48.2% compared with the wild-type, respectively. The gene also regulated nitrogen source utilization, particularly for ammonium sulfate (29.3% inhibition of the knockout). When xylan was the sole carbon source, ΔIrXyn01 showed 12.8% growth inhibition. Neutral xylanase activity in mutants remained low (35–46 nmol/min/mL), compared to 138–142 nmol/min/mL in the wild-type strain and complemented strains. Pathogenicity assays confirmed that the IrXyn01 knockout significantly reduced disease severity, with lower rusty root rot severity in ginseng inoculated with mutants. This study identified IrXyn01 as a virulence gene in I. robusta and improves our understanding of its molecular pathogenesis.
Ya-Kun Zhang, Xiang-Kai Liu, Yi-Meng Wang et al.· Horticulturae· 0 citations
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