Tripartite interactions shape the biocontrol potential of lactic acid bacteria against Ralstonia solanacearum and Fusarium oxysporum f. sp. cubense race 1

Abstract

ABSTRACT This study investigated the antagonistic potential of two lactic acid bacteria (LAB) strains, A15 and A55, against the major banana pathogens Fusarium oxysporum f. sp. cubense race 1 (Foc R1), the causal agent of Fusarium wilt, and Ralstonia solanacearum race 2 (Rs), responsible for Moko disease. In vitro assays revealed significant inhibition of Foc R1 and Rs by both LAB strains, and greenhouse experiments showed that their application reduced the severity and delayed the onset of Fusarium wilt symptoms in Gros Michel banana plants (p < 0.05). However, LAB treatments did not mitigate Moko disease; instead, disease severity increased over time in Rs-infected plants, underscoring that in vitro antagonism does not necessarily translate into effective in planta biocontrol. The results further suggest that LAB-mediated suppression of Foc R1 might be influenced by host factors, such as an induction in plant defences, highlighting the complexity of tripartite interactions in biological control. Although LAB effects were limited to disease suppression rather than plant growth promotion, their integration into broader pest management programmes may enhance sustainability and reduce reliance on chemical controls. Future research should focus on elucidating the biochemical mechanisms underlying LAB activity and optimising application strategies under field conditions.