Abstract
BackgroundRoot-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.ResultsSeventeen 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.ConclusionsMost 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.
Highlights
Root-knot nematodes (Meloidogyne spp.) are the most destructive agricultural pests, which parasitize thousands of different plant species in the world
Preliminary evaluation of the bacterial isolates against Meloidogyne javanica The results of preliminary screening of the 17 bacterial isolates from vermicompost or earthworm showed that in all treatments, the number of galls per gram of infected tomato roots was significantly lower than the untreated control
The egg hatching of the nematode in the presence of Lysinibacillus sp. (W6) and S. daejeonense LV1 was statistically similar to the control
Summary
Root-knot nematodes (Meloidogyne spp.) are the most destructive agricultural pests, which parasitize thousands of different plant species in the world. Root-knot nematodes (Meloidogyne spp.) are the most destructive agricultural pests, which parasitize many plant species of different groups around the world. They are the main subject of extensive research, including studies on biology, plant-nematode interaction, and especially control approaches (Moens et al 2009). Plant growth-promoting rhizobacteria (PGPR) induced systemic resistance by increasing the activity of the defense gene, which caused the decrease in the level of root-knot nematode infection in tomato plants (Vigila et al 2019). These bacteria have been extracted from various substrates including manure, compost, and soil
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