Abstract
Bacillus subtilis DZSY21 isolated from the leaves of Eucommia ulmoides oliv. was labeled by antibiotic marker and found to effectively colonize the leaves of maize plant. Agar diffusion assays and biocontrol effect experiments showed that strain DZSY21 and its lipopeptides had antagonistic activity against Bipolaris maydis, as well as high biocontrol effects on southern corn leaf blight caused by B. maydis. Using MALDI-TOF-MS analysis, we detected the presence of antimicrobial surfactin A, surfactin B, and fengycin in the strain DZSY21. Signaling pathways mediated by DZSY21 were analyzed by testing the expression of key plant genes involved in regulation of salicylic acid (SA) or JA/ET pathways, the defense-related genes PR1 and LOX were concurrently expressed in the leaves of DZSY21-treated plants; this corresponded to slight increase in the expression level of PDF1.2 and decreases in ERF gene transcription levels. The results indicated an induced systemic response that is dependent on the SA and jasmonic acid (JA) pathways. Thus, we hypothesized that the strain DZSY21 inhibits B. maydis by producing antifungal lipopeptides and activating an induced systemic response through SA- and JA-dependent signaling pathways. This work describes a mechanism behind reduced disease severity in plants inoculated with the endophytic bacteria DZSY21.
Highlights
Epidemics of southern corn leaf blight in maize are caused by Bipolaris maydis; these infections are regarded as one of the most destructive foliar diseases due to their extensive damage to crop yield and quality (Wang et al, 2015)
After being cultured for 7 days, the diameter of the colony of the B. maydis treated with the strain DZSY21 was roughly 3 cm (Figure 1B), while the colony of B. maydis treated with water was basically full of Petri dish (Figure 1A)
The isolated endophytic strain DZSY21 was grown in Landy medium for 38 h in order to induce secretion of antifungal lipopeptides
Summary
Epidemics of southern corn leaf blight in maize are caused by Bipolaris maydis; these infections are regarded as one of the most destructive foliar diseases due to their extensive damage to crop yield and quality (Wang et al, 2015). Fungicides and resistant cultivars have been used to control this disease in the field Some fungicides, such as Chlorothalonil, Carbendazim, and Thiophanate-methyl wettable powders are effective in preventing disease (Akgül and Mirik, 2008); the use of chemical fungicides pollutes the environment and catalyzes the development of fungicide-resistant strains (Bajwa et al, 2003). Endophytic bacteria are micro-organisms that colonize healthy plant tissue without causing any apparent symptoms or diseases to the host (Arnold et al, 2003). These strains could exert several beneficial effects on host plants, including conferring resistance against different biotic and abiotic stresses (Kharwar et al, 2008), inducing resistance to plant pathogens, and producing beneficial bioactive substances. There is interest in the use of endophytic bacteria for the biological
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