AUTHOR=Tian Xue-liang , Zhao Xiao-man , Zhao Song-yu , Zhao Jian-long , Mao Zhen-chuan 

TITLE=The Biocontrol Functions of Bacillus velezensis Strain Bv-25 Against Meloidogyne incognita

JOURNAL=Frontiers in Microbiology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2022.843041

DOI=10.3389/fmicb.2022.843041

ISSN=1664-302X

ABSTRACT=<p><italic>Meloidogyne incognita</italic> is obligate parasitic nematode with a wide variety of hosts that causes huge economic losses every year. In an effort to identify novel bacterial biocontrols against <italic>M. incognita</italic>, the nematicidal activity of <italic>Bacillus velezensis</italic> strain Bv-25 obtained from cucumber rhizosphere soil was measured. Strain Bv-25 could inhibit the egg hatching of <italic>M. incognita</italic> and had strong nematicidal activity, with the mortality rate of second-stage <italic>M. incognita</italic> juveniles (J2s) at 100% within 12 h of exposure to Bv-25 fermentation broth. The <italic>M. incognita</italic> genes <italic>ord-1</italic>, <italic>mpk-1</italic>, and <italic>flp-18</italic> were suppressed by Bv-25 fumigation treatment after 48 h. Strain Bv-25 could colonize cucumber roots, with 5.94 × 10<sup>7</sup> colony-forming units/g attached within 24 h, effectively reducing the infection rate with J2s by 98.6%. The bacteria up-regulated the expression levels of cucumber defense response genes <italic>pr1</italic>, <italic>pr3</italic>, and <italic>lox1</italic> and induced resistance to <italic>M. incognita</italic> in split-root trials. Potted trials showed that Bv-25 reduced cucumber root knots by 73.8%. The field experiment demonstrated that disease index was reduced by 61.6%, cucumber height increased by 14.4%, and yield increased by 36.5% in Bv-25–treated plants compared with control. To summarize, <italic>B. velezensis</italic> strain Bv-25 strain has good potential to control root-knot nematodes both when colonizing the plant roots and through its volatile compounds.</p>