Inoculation of wheat bran with nonpathogenic Fusarium species an effective biological control method for Fusarium crown and root rot in asparagus

Fusarium crown and root rot (FCRR), a disease caused by the fungus Fusarium oxysporum f. sp. asparagi, is one of the most destructive diseases affecting asparagus worldwide. Despite some evidence of the suppression of FCRR by several nonpathogenic F. oxysporum sensu lato strains in laboratory experiments, biological control trials in FCRR-infested fields have not consistently demonstrated the effectiveness of these strains. Therefore, we developed and assessed a novel method of using nonpathogenic F. oxsyporum strains for the biological control of FCRR in the field. Two strains (SM007 and FAoc5) effectively suppressed FCRR in young asparagus seedlings were cultured on wheat bran medium. Then, the material was then inoculated into mature second-year seedlings before transplanting them into infested soil. Both strains successfully suppressed FCRR. Next, we evaluated the impact of irrigation and on this system in greenhouse experiments utilizing SM007. We found that the density of the fungus colonizing in the wheat bran played a pivotal role in disease suppression. Both strains utilized in this study also exhibited the capacity to impede chlamydospore germination of the pathogen when glucose was incorporated into soil. This suggests that nutrient competition between nonpathogenic strains and the pathogen plays a crucial role in disease suppression, highlighting the importance of maintaining an optimal balance between these microorganisms in organic matter-based applications of biocontrol agents.