Interaction of bacteria Bacillus subtilis, B. cereus and Pseudomonas fluorescens CHA0 with the model nematode, Caenorhabditis elegans, and use of these bacteria in biocontrol of Meloidogyne javanica

In this study, the interaction of Bacillus subtils, B. cereus, and Pseudomonas fluorescens CHA0 with the bacteriovorus nematode Caenorhabditis elegans was investigated in in-vitro condition. Possibilities of the survival and reproduction, the attraction and feeding of C. elegans on the bacteria, and the effect of volatile compounds and antibiotics of the bacteria on C. elegans were examined. The efficiency of the bacteria on controlling Meloidogyne javanica was studied by evaluating the number of galls and egg masses per plant, gall-diameter per plant, and the number of eggs per egg mass. Then, the most effective bacterium was used for the induction of plant defence responses. The results showed that C. elegans is not able to survive and reproduce on the colony of B. cereus and P. fluorescens CHA0. Although, in the normal condition, C. elegans did not feed on B. cereus, when the nematode was left hungry it started to eat the bacterium which, however, caused its death. Volatile compounds and antibiotics of B. cereus and P. fluorescens CHA0 caused 100% C. elegans larval mortality after 24 or 48 hours. All three bacteria caused a significant reduction (p<0.05) in all indicators of M. javanica pathogenicity while the highest efficacy in controlling the nematode was observed for P. fluorescens CHA0. Biochemical analyses showed that inoculating plants with P. fluorescens CHA0 and/or M. javanica caused a significant increase (p<0.05) of catalase in the plants.