A sustainable biocontrol approach using rhizosphere bacterial strains against Meloidogyne javanica on tomato

Abstract

The root-knot nematode (RKN), Meloidogyne javanica, causes severe damage to a wide variety of crops. These nematodes significantly reduce tomato yield globally, causing symptoms such as stunted growth, galls on roots, chlorosis, and wilting, ultimately leading to host death. Classical nematode control methods, such as the application of chemical nematicides, are very effective; however, their use is limited due to conflicts with sustainable agriculture. Therefore, biological methods, are gaining attention as more environmentally friendly options. In the present study, 47 strains of bacteria were isolated from the rhizosphere of RKN-infected plants. The effect of these strains was studied on egg hatching and second stage infective juveniles (J2s) mortality of M. javanica, in vitro. Then, three holes were made in the soil around the roots of non-inoculated and nematode inoculated tomato plants and a suspension of 15 mL of three isolates with the greatest negative effect on hatching and J2s mortality (10⁷ CFU/ml), was poured into the holes. Stenotrophomonas maltophilia CPHE1, Peribacillus frigoritolerans Rhs-L31 and Bacillus cereus Pt0-RL12 improved the vegetative indices of inoculated plants compared to control plants. These strains significantly reduced nematode hatching and significantly increased mortality of nematode J2s; and in greenhouse pot experiments significantly reduced the number of nematode eggs and egg masses, root galls, and nematode reproduction factor. In each case, inoculation with the bacterial strains significantly increased peroxidase and superoxide dismutase activity, and decreased catalase activity in tomato roots infected with M. javanica. The present study indicates the potential of these bacterial strains for biocontrol of M. javanica on tomato.