AUTHOR=Wang Hongwei , Cai Xiao-Yu , Xu Man , Tian Feng 

TITLE=Enhanced Biocontrol of Cucumber Fusarium Wilt by Combined Application of New Antagonistic Bacteria Bacillus amyloliquefaciens B2 and Phenolic Acid-Degrading Fungus Pleurotus ostreatus P5

JOURNAL=Frontiers in Microbiology

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2021.700142

DOI=10.3389/fmicb.2021.700142

ISSN=1664-302X

ABSTRACT=<p>Continuous monoculture of cucumber (<italic>Cucumis sativus</italic> L.) typically leads to the frequent incidence of Fusarium wilt caused by <italic>Fusarium oxysporum</italic> f. sp. <italic>cucumerinum</italic> (FOC). As potent allelochemicals, phenolic acids are believed to be associated with soilborne diseases. This study aimed to investigate the effect of single or co-inoculation of antagonistic bacteria <italic>Bacillus amyloliquefaciens</italic> B2 and phenolic acid-degrading fungus <italic>Pleurotus ostreatus</italic> P5 on the suppression of cucumber Fusarium wilt. The strain B2 was identified as <italic>B. amyloliquefaciens</italic> based on biochemical, physiological, and 16<italic>S</italic> rDNA and <italic>gyrB</italic> gene sequence analyses. Strain B2 showed indole-3-acetic acid (IAA) and siderophore production and phosphate solubilization in <italic>in vitro</italic> assays. Scanning electron microscope (SEM) imaging showed the ability of strain B2 to adhere to the root surface of cucumber. <italic>P. ostreatus</italic> P5 could effectively degrade mixed phenolic acids as its sole source of carbon and energy for growth in liquid medium. In a pot experiment, four treatments were established as follows: (1) CK, uninoculated control; (2) B2, inoculation of strain B2; (3) P5, inoculation of strain P5; and (4) B2 + P5, co-inoculation of strain B2 and strain P5. At the end of the 60-day pot experiment, the B2, P5, and B2 + P5 treatments significantly reduced disease incidence by 48.1, 22.2, and 63.0%, respectively, compared to the CK treatment (<italic>p</italic> &lt; 0.05). All three inoculation treatments significantly increased the growth of cucumber seedlings and suppressed the FOC population compared to the control (<italic>p</italic> &lt; 0.05). High-performance liquid chromatography (HPLC) analysis showed that total phenolic acids were decreased by 18.9, 35.9, and 63.2% in the B2, P5, and B2 + P5 treatments, respectively. The results from this study suggest that combined application of <italic>B. amyloliquefaciens</italic> B2 and <italic>P. ostreatus</italic> P5 could be a promising strategy for suppressing Fusarium wilt and improving plant growth of cucumber seedlings under continuous cropping conditions.</p>