Potential of Bacillus species against Meloidogyne javanica parasitizing eggplant ( Solanum melongena L.) and induced biochemical changes

Aims The biocontrol potential of three Bacillus species, namely Bacillus subtilis (BS), Bacillus firmus (BF), and Bacillus coagulans (BC) was tested against the root-knot nematode Meloidogyne javanica (Treub) Chitwood in eggplants ( Solanum melongena L.). Plant growth and biochemical effects were also measured in these interactions. Methods Bacillus species were inoculated in soil around the seedlings of eggplants ( Solanum melongena L.) with and without nematodes in a greenhouse experiment. Plant growth, biochemical changes, and nematode parasitism were observed at 15 and 45 days after inoculation (DAI). Results BC significantly enhanced plant growth, chlorophyll “b” and total chlorophyll contents, and polyphenol oxidase (PPO) activity in the leaves of eggplants, while BS showed greatest reduction in root-knot nematode parasitism. Non-infected and untreated control (C−) plants showed lesser chlorophyll “b,” carotenoids, soluble protein contents, and guaiacol peroxidase but higher catalase and PPO activities compared to infected and untreated controls (C+) at 15 and 45 DAI. Superoxide dismutase activity declined in most of the treated plants at 45 DAI following rise at 15 DAI. Ascorbate peroxidase activity increased at 45 DAI compared to 15 DAI in C− and C+ plants. PAL activity was greatly enhanced at 45 DAI in all treatments and controls over that at 15 DAI. Conclusions BC is a potentially plant growth-promoting bacteria although it was less effective against nematode infection compared to BS. Enzymes activities varied with infection and DAI. BC at 15 DAI in general increased the activity of most of the stress enzymes and thereby overcoming the effect of nematode parasitism.