Bacillus lipopeptide-mediated biocontrol of peanut stem rot caused by Athelia rolfsii

Abstract

IntroductionPeanut (Arachis hypogaea L.) is a widespread oilseed crop of high agricultural importance in tropical and subtropical areas. It plays a major role in the food supply in the Democratic Republic of Congo (DRC). However, one major constraint in the production of this plant is the stem rot (white mold or southern blight) disease caused by Athelia rolfsii which is so far controlled mainly using chemicals. Considering the harmful effect of chemical pesticides, the implementation of eco-friendly alternatives such as biological control is required for disease management in a more sustainable agriculture in the DRC as in the other developing countries concerned. Bacillus velezensis is among the rhizobacteria best described for its plant protective effect notably due to the production of a wide range of bioactive secondary metabolites. In this work, we wanted to evaluate the potential of B. velezensis strain GA1 at reducing A. rolfsii infection and to unravel the molecular basis of the protective effect.Results and discussionUpon growth under the nutritional conditions dictated by peanut root exudation, the bacterium efficiently produces the three types of lipopeptides surfactin, iturin and fengycin known for their antagonistic activities against a wide range of fungal phytopathogens. By testing a range of GA1 mutants specifically repressed in the production of those metabolites, we point out an important role for iturin and another unidentified compound in the antagonistic activity against the pathogen. Biocontrol experiments performed in greenhouse further revealed the efficacy of B. velezensis to reduce peanut disease caused by A. rolfsii both via direct antagonism against the fungus and by stimulating systemic resistance in the host plant. As treatment with pure surfactin yielded a similar level of protection, we postulate that this lipopeptide acts as main elicitor of peanut resistance against A. rolfsii infection.

Exploring Synergistic Effects of Levan and Levan‐MetabolizingBacillaceae in Promoting Growth and Enhancing Immunity of Tomato and Wheat

“…These compounds are believed to play a key role in reducing disease (Touré et al, 2004). This strain showed good colonization ability potential on peanut roots and produced a wide range of bioactive secondary metabolites against Athelia rolfsii (Korangi Alleluya et al, 2023). Interestingly, lipopeptide signatures were further fine‐tuned when cocultured with Trichoderma harzianum (Fifani et al, 2022).…”

“…stand out as the most extensively studied organisms in the context of the rhizosphere (Boulahouat et al, 2023), but they may be equally important in the phyllosphere context as well (Fessia et al, 2022). Commercial plant protection formulations, for instance with Bacillus thuringiensis (as bio‐insecticide), Bacillus subtilis , Bacillus amyloliquefaciens and Bacillus velezensis gain importance in crop protection (Savary et al, 2019; Samaras et al, 2021a,b; Korangi Alleluya et al, 2023; Ortiz & Sansinenea, 2023). Many species of the Bacillaceae family, especially Bacillus and Priestia species isolated from the plant rhizosphere, show seed germination and plant growth‐promoting activity, hence they are called plant growth‐promoting rhizobacteria (PGPR, Savary et al, 2019).…”

Bacillus-based biocontrol beyond chemical control in central Africa: the challenge of turning myth into reality

“…In the same study, S499 was able to efficiently reduce disease severity (39-67%) caused by these fungi in greenhouse and field conditions ( Kulimushi et al., 2018 ). In addition, B. velezensis GA1 and its cyclic lipopeptides played an important role in the control of peanut stem rot disease caused by Athelia rolfsii , providing up to 60% of protection ( Korangi Alleluya et al., 2023 ).…”