Biocontrol potential of bacterial isolates from vermicompost and earthworm against the root-knot nematode Meloidogyne javanica infecting tomato plants

Background Root-knot nematodes (Meloidogyne spp.) are the most destructive agricultural pests, which parasitize thousands of different plant species in the world. Using antagonistic bacteria can be a potential alternative to hazardous chemical nematicides. This study was conducted to evaluate the biocontrol activities of the bacteria isolated from vermicompost and earthworm against M. javanica in infected tomato plants. Results Seventeen bacteria were isolated from vermicompost and earthworm. Their antagonistic effects were tested against the root-knot nematode M. javanica in laboratory and in glasshouse experiments. In the preliminary screening test, 8 bacterial isolates significantly caused more than 50% decrease in reproduction factor (Rf) of the nematode on tomato plants. Six isolates with more than 60% reduction in the nematode Rf were selected and identified as follows: Lysinibacillus fusiformis C1, Bacillus megaterium C3, B. safensis VW3, Pseudomonas resinovorans VW4, Lysinibacillus sp. VW6, and Sphingobacterium daejeonense LV1 by 16S rRNA gene sequencing. The isolates B. megaterium C3, B. safensis VW3, P. resinovorans VW4, and L. fusiformis C1 inhibited the nematode egg hatching by 20–28%, and Lysinibacillus sp. VW6 and L. fusiformis C1 caused 15 and 20% mortality of the second-stage juveniles in vitro. In a glasshouse, the 6 bacterial isolates reduced the nematode Rf by 47–66%, and P. resinovorans VW4 was the most effective isolate. However, B. safensis VW3, B. megaterium C3, and L. fusiformis C1 had the best effect on plant growth. Conclusions Most of the bacteria isolated from earthworm or vermicompost had nematicidal properties. This study provided empirical evidence of the nematicidal potential of isolates Lysinibacillus fusiformis C1, Pseudomonas resinovorans VW4, and Sphingobacterium daejeonense LV1 and the antagonistic activities of Bacillus megaterium C3 and B. safensis VW3 against Meloidogyne javanica.

Draft Genome Sequence of Mn(II)-Oxidizing Pseudomonas resinovorans Strain MO-1

ABSTRACT Pseudomonas resinovorans strain MO-1, which possesses a high ability to oxidize Mn(II), has been isolated from oligotrophic pond sediment. The draft genome sequence consists of 6,252,942 bp and has a G+C content of 63.4%. Strain MO-1 has 5,694 coding sequences, including 13 putative Mn(II) oxidation genes.

Beneficial bacterial strains on Agaricus blazei cultivation

The objective of this work was to evaluate the effects of six bacterial strains isolated from Agaricus blazei (ABM) on its cultivation. The six strains were characterized as to their effects on the productivity, polysaccharide-protein complex (PSPC), and polysaccharide contents of ABM cultured on sterilized casing soils. Three isolates enhanced ABM mycelium growth. Inoculation of Arthrobacter sp. or Exiguobacterium sp. on sterile peat casing soil resulted in 64% increase in ABM mushroom total fresh matter yield compared to the uninoculated control. Inoculation of Exiguobacterium sp., Microbacterium esteraromaticum or Pseudomonas resinovorans on sterilized loamy casing soil resulted in 62, 95, and 59% increase in ABM mushroom total fresh matter yield, respectively. The PSPC content in ABM increased 7 to 10% in casing soil inoculated with five of the six isolates compared to the uninoculated control. Exiguobacterium sp. inoculated on casing soil resulted in a mushroom-polysaccharide content 15% higher than the control. Moreover, inoculation of five of the six isolates on the casing soil reduced the harvesting time from 10 to 27 days. The evaluated beneficial microbes improve the yield, PSPC, and polysaccharide contents, besides reducing the harvesting time in ABM culture.