AUTHOR=Hu Yanfeng , You Jia , Wang Yu , Long Yong , Wang Siru , Pan Fengjuan , Yu Zhenhua 

TITLE=Biocontrol efficacy of Bacillus velezensis strain YS-AT-DS1 against the root-knot nematode Meloidogyne incognita in tomato plants

JOURNAL=Frontiers in Microbiology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2022.1035748

DOI=10.3389/fmicb.2022.1035748

ISSN=1664-302X

ABSTRACT=<p>Root-knot nematodes (RKNs; <italic>Meloidogyne</italic> spp.), one of the most economically important plant-parasitic nematodes (PPNs), cause severe yield and quality losses in agriculture annually. The application of biological control agents is an environmentally safe and effective approach to control RKNs. Here, we report the genomic characteristics of a <italic>Bacillus velezensis</italic> strain YS-AT-DS1 (<italic>Bv-DS1</italic>) isolated from the tidal soil, revealing that it has a 4.73 Mb circular chromosome with an average GC-content of 46.43%, 3,977 genes, 86 tRNAs, and 27 rRNAs, and contains secondary metabolite clusters for producing antimicrobial compounds. <italic>In vitro</italic> assays indicated that <italic>Bv-DS1</italic> has not only antagonistic activities against fungal pathogens, but also shows nematicidal activity, with a mortality rate of 71.62% mortality rates in second-stage juvenile (J2s) <italic>Meloidogyne incognita</italic>. We then focused on the biocontrol efficiency of <italic>Bv-DS1</italic> against <italic>M. incognita</italic> in pot assays. Preinoculation with <italic>Bv-DS1</italic> enhanced tomato growth, and significantly reduced the infection rate of J2s, and the number of galls and egg masses on tomato roots. The underlying mechanism in <italic>Bv-DS1-</italic>induced resistance to <italic>M. incognita</italic> was further investigated through split-root experiments, and analysing the expression of the genes related to jasmonic acid (JA), salicylic acid (SA), and the tonoplast intrinsic protein (TIP). The results indicated that <italic>Bv-DS1</italic> could not activate host systemic-induced resistance (ISR) in the split-root system of tomatoes. Additionally, the expression of JA- (<italic>LOX D</italic> and <italic>MC</italic>) and SA- (<italic>PAL2</italic> and <italic>PR</italic>) responsive genes did not change in <italic>Bv-DS1</italic>-pretreated plants at 3 and 14 days after nematode inoculation. The presented data showed that JA-and SA-dependent pathways were not required for the biocontrol action of the <italic>Bv-DS1</italic> against RKN. The <italic>TIP</italic> genes, responsible for transport of water and small substrates in plants, have previously been shown to negatively regulate the parasitism of PPNs. Surprisingly, <italic>Bv-DS1</italic> compromised the downregulation of <italic>TIP1.1</italic> and <italic>TIP1.3</italic> by <italic>M. incognita</italic>. Together, our data suggest that <italic>Bv-DS1</italic> exhibits a dual effect on plant growth promotion and protection against RKN, possibly related to the regulation of water and solute transport <italic>via TIPs</italic>. Thus, the <italic>Bv-DS1</italic> strain could be used as a biocontrol agent for RKN control in sustainable agriculture.</p>