Bacillus and its metabolites as biocontrol agents for Xanthomonas translucens pv. undulosa

Details

Supervisors

Bragard, Claude ; Lengrand, Salomé

Faculty

Faculté des bioingénieurs

Degree label

Master [120] : bioingénieur en sciences agronomiques, à finalité spécialisée

Abstract

enXanthomonas translucens pv. undulosa (Xtu), the causal agent of bacterial leaf streak and black chaff in wheat, is able to cause significant yield losses on small grain cereals. Its impact is expected to increase under climate change, while growing restrictions on chemical pesticides highlight the need for sustainable control alternatives. Biological control based on antagonistic microorganisms offers a promising environmentally friendly strategy for managing Xtu and improving wheat disease control. This master's thesis investigated the antagonistic activity of the strains Bacillus subtilis and Bacillus nakamurai against Xtu, and investigated the role of their secondary metabolites. The use of metabolite-deficient mutant strains helped to unravel the metabolites involved in the antagonistic activity against Xtu, in cell-based competition assays. Cell-free supernatant assays combined with UPLC-MS quantification of bacilysin allowed the contribution of individual metabolites to be assessed. Interactions between biosynthetic pathways were further explored, in particular the metabolic and regulatory links between bacilysin, bacillibactin and surfactin biosynthesis. In planta assays were conducted to evaluate the biocontrol potential of the antagonistic, phyllosphere-isolated Bacillus strains and B. nakamurai against Xtu on wheat, across cultivars with differing susceptibility. Overall, this work aims to identify key antimicrobial metabolites active against Xtu and to clarify their regulatory context, providing a basis for future strategies aimed at optimizing biocontrol approaches for sustainable management of wheat bacterial leaf streak.