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

Background: Root-knot nematodes (Meloidogynespp.) 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. javanicain infected tomato plants. Results: Seventeen bacteria were isolated from vermicompost and earthworm. Their antagonistic effects were tested against the root-knot nematode M. javanicain 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 fusiformisC1, Bacillus megateriumC3, B. safensisVW3, Pseudomonas resinovoransVW4, Lysinibacillussp. VW6, and Sphingobacterium daejeonenseLV1 by 16S rRNA gene sequencing. The isolates B. megateriumC3, B. safensisVW3, P. resinovoransVW4, and L. fusiformisC1 inhibited the nematode egg hatching by 20–28%, and Lysinibacillussp. VW6 and L. fusiformisC1 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. resinovoransVW4 was the most effective isolate. However, B. safensisVW3, B. megateriumC3, and L. fusiformisC1 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 fusiformisC1, Pseudomonas resinovoransVW4, and Sphingobacterium daejeonenseLV1 and the antagonistic activities of Bacillus megateriumC3 and B. safensisVW3 against Meloidogyne javanica.