Plant Growth-Promoting and Antifungal Activity of Bacillus spp. Isolated from Wild Wheat Aegilops cylindrica Against Fusarium culmorum in Cultivated Wheat

Wild grasses such as Aegilops cylindrica are a promising source of epiphytic bacteria with plant growth-promoting (PGP) properties and those that contribute to biocontrol. Two bacterial strains from the phyllosphere of A. cylindrica were isolated and identified as Bacillus mojavensis WP4 and Bacillus siamensis WS6. Both strains produced auxins (1.56–5.09 μg/mL) and siderophores and dissolved phosphates. They inhibited the growth of F. culmorum in vitro and increased the biomass of wheat seedlings by up to 2.9 times, although the effects were variety-specific (Tulaykovskaya 10 variety). Neither strain exhibited multiple drug resistance. B. mojavensis WP4 and B. siamensis WS6 are multifunctional strains that stimulate plant growth and exhibit biocontrol activity against F. culmorum during the germination stage. But visible protection of young plants (not seeds) was not observed; however, bacterial treatment restored photosystem II activity (Fv/Fm and Y(II)) in infected plants. Microscopic examination confirmed root colonization. Future research should focus, on the one hand, on conducting experiments in greenhouses and under field conditions, and on the other hand, on investigating the molecular mechanisms underlying the interaction between the bacterium (Bacillus sp. strain), the plant (wheat), and the phytopathogen (F. culmorum).