Abstract An increasing amount of attention has been directed towards beneficial microorganisms capable of producing bioactive substances, which can promote the growth of crops and enhance their defense mechanisms. This study focused on the growth-promoting effects of Bacillus velezensis HE-23, isolated from the roots of Aucklandia lappa, on tomatoes (Solanum lycopersicum L.). The growth-promotion experiments indicated that the fermentation broth of HE-23 significantly facilitated tomato seed germination and seedling growth. Specifically, the root length, above-ground dry weight, below-ground fresh weight, and below-ground dry weight were enhanced by 68.08, 80.08, 84.03, and 70.65%, respectively. In-depth analysis revealed that the fermentation broth of HE-23 could induce the expression of genes associated with the gibberellin (GA), indole-3-acetic acid (IAA), and mitogen-activated protein kinase (MAPK) cascade signaling pathways. Notably, the expression levels of SlFZY1, SlGA3ox2, and SlGA20ox2 were upregulated by 2.73, 2.99, and 5.3 fold respectively. These findings provide crucial insights into the growth-promoting mechanism of the HE-23 strain, and also lay a substantial foundation for its development as a microbial inoculant for vegetable and fruit crops.
W. Jian, Y. Qin, Y. Chen et al.· Russian journal of plant phy...· 0 citations
Verticillium dahliae is a destructive soil-borne fungus with a broad host range, and its persistence in soil complicates control. Current measures, mainly resistant cultivars and chemicals, are limited and environmentally risky, promoting biocontrol as a green alternative. Here, we investigated the biocontrol mechanisms of Bacillus velezensis L33a against V. dahliae JR2 in tomato. In vitro assays on PDA plates at 26°C for 9 d showed that L33a inhibited JR2 by 58.6%, caused hyphal malformation and disruption, and its volatile organic compounds suppressed pathogen growth. In pot experiments, tomato roots dipped in JR2 suspension (1 ×10⁶ CFU/mL) for 30 min at 7 d after transplanting and grown for 21 d achieved 60.9% control efficacy. Physiological assays indicated reduced peroxidase and catalase activities, while qPCR revealed that L33a alone upregulated JA signaling (SlJAZ1, SlMYC2, SlPI II) and antioxidant (SlCAT, SlAPX) genes, with further enhancement upon JR2 co-treatment. To track their interactions, we generated GFP-labeled JR2 and RFP-labeled L33a; dual fluorescence labeling showed that L33a endophytically colonized Arabidopsis thaliana roots and competed with JR2 for the same niche, correlating with reduced pathogen colonization. Integrated metabolomic and transcriptomic analysis further revealed that L33a treatment altered pathways related to ABC transporters, amino acid metabolism, cell wall integrity, and energy metabolism in JR2, with tyrosine metabolism significantly enriched at both levels. Collectively, these findings suggest that L33a is a promising biocontrol strain for green management of tomato Verticillium wilt.
