Biocontrol Efficacy and Mechanism of Action of Bacillus velezensis L33a Against Postharvest Sweet Potato Black Rot

Jian, Wei; Li, Yuanyuan; Zhu, Yaqian; Yao, Qing; Qin, Youcheng; Liu, Haiying; Zhang, Jing; Qiu, Guoyang; Gui, Qihang; Zhao, Zhengwu

doi:10.3390/jof12070492

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Biocontrol Efficacy and Mechanism of Action of Bacillus velezensis L33a Against Postharvest Sweet Potato Black Rot

by

Wei Jian

^*,†

,

Yuanyuan Li

^†,

Yaqian Zhu

,

Qing Yao

,

Youcheng Qin

,

Haiying Liu

,

Jing Zhang

,

Guoyang Qiu

,

Qihang Gui

and

Zhengwu Zhao

^*

Key Laboratory of Plant Environmental Adaptation Biology of Chongqing, College of Life Sciences, Chongqing Normal University, Chongqing 401331, China

^*

Authors to whom correspondence should be addressed.

^†

These authors contributed equally to this work.

J. Fungi 2026, 12(7), 492; https://doi.org/10.3390/jof12070492

Submission received: 27 May 2026 / Revised: 21 June 2026 / Accepted: 2 July 2026 / Published: 3 July 2026

(This article belongs to the Special Issue Postharvest Fungi: Control of Fungal Diseases in Fruit and Vegetables)

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Abstract

Black spot disease caused by Ceratocystis fimbriata (C. fimbriata)is a severe postharvest disease of sweet potatoes. This study evaluated the biocontrol potential of Bacillus velezensis (B. velezensis) L33a against this pathogen. Confrontation assays showed that L33a inhibited mycelial growth by 82.83%. FDA/PI staining and scanning electron microscopy revealed that L33a disrupted cell membrane integrity and caused severe mycelial deformation. Co-culture experiments indicated that L33a altered the expression of key pathogenic genes in C. fimbriata. Volatile organic compounds (VOCs) from L33a inhibited the pathogen by 77.78%, outperforming cell-free supernatant (CFS). VOCs primarily suppressed spore germination, with phenylethanol (PEA) and octanoic acid achieving 100% inhibition. In planta tests on sweet potato tubers showed that both L33a culture and VOCs significantly reduced lesion expansion. Using qPCR analysis, we found that L33a activated defense-related genes in tissues around wounds, particularly those involved in the jasmonic acid (JA) signaling pathway. In summary, B. velezensis L33a effectively controls sweet potato black rot through multiple mechanisms: direct antifungal activity, inhibition of spore germination, modulation of pathogen gene expression, and induction of host defense responses. It represents a promising natural inhibitor for postharvest disease management.

Keywords: Bacillus velezensis; sweet potato black spot disease; biological control; volatile organic compounds; Ceratocystis fimbriata

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MDPI and ACS Style

Jian, W.; Li, Y.; Zhu, Y.; Yao, Q.; Qin, Y.; Liu, H.; Zhang, J.; Qiu, G.; Gui, Q.; Zhao, Z. Biocontrol Efficacy and Mechanism of Action of Bacillus velezensis L33a Against Postharvest Sweet Potato Black Rot. J. Fungi 2026, 12, 492. https://doi.org/10.3390/jof12070492

AMA Style

Jian W, Li Y, Zhu Y, Yao Q, Qin Y, Liu H, Zhang J, Qiu G, Gui Q, Zhao Z. Biocontrol Efficacy and Mechanism of Action of Bacillus velezensis L33a Against Postharvest Sweet Potato Black Rot. Journal of Fungi. 2026; 12(7):492. https://doi.org/10.3390/jof12070492

Chicago/Turabian Style

Jian, Wei, Yuanyuan Li, Yaqian Zhu, Qing Yao, Youcheng Qin, Haiying Liu, Jing Zhang, Guoyang Qiu, Qihang Gui, and Zhengwu Zhao. 2026. "Biocontrol Efficacy and Mechanism of Action of Bacillus velezensis L33a Against Postharvest Sweet Potato Black Rot" Journal of Fungi 12, no. 7: 492. https://doi.org/10.3390/jof12070492

APA Style

Jian, W., Li, Y., Zhu, Y., Yao, Q., Qin, Y., Liu, H., Zhang, J., Qiu, G., Gui, Q., & Zhao, Z. (2026). Biocontrol Efficacy and Mechanism of Action of Bacillus velezensis L33a Against Postharvest Sweet Potato Black Rot. Journal of Fungi, 12(7), 492. https://doi.org/10.3390/jof12070492

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Biocontrol Efficacy and Mechanism of Action of Bacillus velezensis L33a Against Postharvest Sweet Potato Black Rot

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