AUTHOR=Kim Bora , Park Ae Ran , Song Chan Woo , Song Hyohak , Kim Jin-Cheol 

TITLE=Biological Control Efficacy and Action Mechanism of Klebsiella pneumoniae JCK-2201 Producing Meso-2,3-Butanediol Against Tomato Bacterial Wilt

JOURNAL=Frontiers in Microbiology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2022.914589

DOI=10.3389/fmicb.2022.914589

ISSN=1664-302X

ABSTRACT=<p>Bacterial wilt caused by <italic>Ralstonia solanacearum</italic> is a fatal disease that affects the production of tomatoes and many other crops worldwide. As an effective strategy to manage bacterial wilt, biological control agents using plant growth-promoting rhizobacteria (PGPR) are being developed. In this study, we screened 2,3-butanediol (BDO)-producing PGPR to control tomato bacterial wilt and investigated the action mechanism of the disease control agent. Of the 943 strains isolated from soil, <italic>Klebsiella pneumoniae</italic> strain JCK-2201 produced the highest concentration of 2,3-BDO. The culture broth of <italic>K. pneumoniae</italic> JCK-2201 did not show any direct activity on <italic>R. solanacearum in vitro</italic>, but a 100-fold dilution effectively controlled tomato bacterial wilt with a control value of 77% <italic>in vivo</italic>. Fermentation utilizing <italic>K. pneumoniae</italic> JCK-2201 was optimized to produce 48 g/L of meso-2,3-BDO, which is 50% of the sucrose conversion efficiency. In addition, the control efficacy and mechanism of meso-2,3-BDO produced by JCK-2201 in tomato bacterial wilt were determined by comparative analysis with <italic>Bacillus licheniformis</italic> DSM13 producing meso-2,3-BDO and <italic>B. licheniformis</italic> DSM13 <italic>ΔalsS</italic> that did not produce 2,3-BDO, as the step of converting pyruvate to α-acetolactate was omitted. Tomato seedlings treated with the <italic>K. pneumoniae</italic> JCK-2201 (500-fold dilution) and <italic>B. licheniformis</italic> DSM13 (100-fold dilution) culture broth produced meso-2,3-BDO that significantly reduced <italic>R. solanacearum</italic>-induced disease severity with control values of 55% and 63%, respectively. The formulated meso-2,3-BDO 9% soluble concentrate (SL; 1,000-fold dilution) showed 87% control against tomato bacterial wilt in the field condition. <italic>Klebsiella pneumoniae</italic> JCK-2201 and <italic>B. licheniformis</italic> DSM13 treatment induced the expression of plant defense marker genes, such as <italic>LePR1</italic>, <italic>LePR2</italic>, <italic>LePR5</italic>, <italic>LePR3</italic>, and <italic>PI-II</italic>, in the salicylic acid and jasmonic acid signaling pathways at 4 days after inoculation. These results show that 2,3-BDO-producing bacteria and 2,3-BDO are potential biological control agents that act through induction of resistance for controlling tomato bacterial wilt.</p>