BMC plant biology · 2026
Harnessing an endophytic Bacillus strain closely related to Bacillus velezensis for biocontrol of twig blight in bayberry caused by Pestalotiopsis versicolor.
СтатьяНазвание и аннотация: Перевод в очереди
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Ibrahim Ezzeldin, Nasser Raghda, Kafsheer Doaa A, Zhu Hequan, Alzunaidy Nada A, Allemailem Khaled S, Al-Megrin Wafa Abdullah I, Wang Dan, Lin Haiping
Аннотация
BACKGROUND: Twig blight disease caused by Pestalotiopsis versicolor threatens bayberry (Myrica rubra) cultivation in China, prompting extensive reliance on chemical fungicides with limited long-term efficacy. This study investigated the potential of endophytic bacteria isolated from bayberry leaves as sustainable biocontrol agents against this pathogenic fungus.
RESULTS: An endophytic bacterium designated strain Bay9 was isolated from healthy bayberry leaves and identified as a Bacillus sp. closely related to Bacillus velezensis based on 16 S rRNA gene sequence analysis. Bay9 exhibited strong antifungal activity against P. versicolor in vitro and showed disease-suppressive effects under semi-controlled greenhouse conditions. On potato dextrose agar (PDA) and in potato dextrose broth (PDB), inhibition rates reached 74.44% and 87.65%, respectively, accompanied by severe ultrastructural damage to fungal hyphae observed by electron microscopy. Cell-free supernatants (CFSs) of Bay9 exhibited concentration-dependent antifungal activity, with inhibition rates of 15.77%, 34.99%, 66.74%, and 98.82% at concentrations of 2.5%, 5%, 10%, and 20% (v/v), respectively. CFSs at EC50 and EC90 concentrations (7.30% and 17.43%, respectively) significantly reduced spore production and germination, induced leakage of intracellular nucleic acids and proteins consistent with membrane perturbation and leakage, but not direct evidence of a defined molecular mechanism and substantially reduced colony formation. In detached leaf assays, EC50 and EC90 treatments reduced lesion development by 65.31% and 94.58%, respectively. Under semi-controlled greenhouse conditions, Bay9 treatment significantly reduced disease incidence (from 97% to 49.33%) and disease severity index (from 82.19% to 38.69%) compared with pathogen-inoculated plants (p < 0.05), without causing phytotoxic effects on bayberry saplings.
CONCLUSIONS: Bay9 exhibited strong antifungal activity associated with multiple putative mechanisms, potentially involving siderophore production, hydrolytic enzyme activities (protease, amylase, and lipase), and lipopeptide-related metabolites, as suggested by biochemical assays and MALDI-TOF-MS-based tentative identification of surfactin-, iturin-, and fengycin-like compounds. Collectively, these findings suggest that Bay9 has potential as a biocontrol agent against P. versicolor under laboratory, detached-leaf, and semi-controlled greenhouse conditions. However, further studies are required to elucidate the underlying molecular mechanisms and to validate its efficacy under field conditions before practical application can be recommended.
RESULTS: An endophytic bacterium designated strain Bay9 was isolated from healthy bayberry leaves and identified as a Bacillus sp. closely related to Bacillus velezensis based on 16 S rRNA gene sequence analysis. Bay9 exhibited strong antifungal activity against P. versicolor in vitro and showed disease-suppressive effects under semi-controlled greenhouse conditions. On potato dextrose agar (PDA) and in potato dextrose broth (PDB), inhibition rates reached 74.44% and 87.65%, respectively, accompanied by severe ultrastructural damage to fungal hyphae observed by electron microscopy. Cell-free supernatants (CFSs) of Bay9 exhibited concentration-dependent antifungal activity, with inhibition rates of 15.77%, 34.99%, 66.74%, and 98.82% at concentrations of 2.5%, 5%, 10%, and 20% (v/v), respectively. CFSs at EC50 and EC90 concentrations (7.30% and 17.43%, respectively) significantly reduced spore production and germination, induced leakage of intracellular nucleic acids and proteins consistent with membrane perturbation and leakage, but not direct evidence of a defined molecular mechanism and substantially reduced colony formation. In detached leaf assays, EC50 and EC90 treatments reduced lesion development by 65.31% and 94.58%, respectively. Under semi-controlled greenhouse conditions, Bay9 treatment significantly reduced disease incidence (from 97% to 49.33%) and disease severity index (from 82.19% to 38.69%) compared with pathogen-inoculated plants (p < 0.05), without causing phytotoxic effects on bayberry saplings.
CONCLUSIONS: Bay9 exhibited strong antifungal activity associated with multiple putative mechanisms, potentially involving siderophore production, hydrolytic enzyme activities (protease, amylase, and lipase), and lipopeptide-related metabolites, as suggested by biochemical assays and MALDI-TOF-MS-based tentative identification of surfactin-, iturin-, and fengycin-like compounds. Collectively, these findings suggest that Bay9 has potential as a biocontrol agent against P. versicolor under laboratory, detached-leaf, and semi-controlled greenhouse conditions. However, further studies are required to elucidate the underlying molecular mechanisms and to validate its efficacy under field conditions before practical application can be recommended.