Assessment of plant defence induction and biocontrol potential of Bacillus megaterium wr101 against Meloidogyne javanica

Abstract

Summary The aim of this study was to evaluate biological control ability and induction of plant defence by Bacillus megaterium wr101, isolated from wheat rhizosphere, on disease severity induced by Meloidogyne javanica on cucumber. In addition, changes in some plant defence compounds (such as peroxidase, polyphenol oxidase, catalase, hydrogen peroxide (H2O2) and accumulation of total phenolic compounds) induced by B. megaterium wr101 and M. javanica were also evaluated. Results showed that application of B. megaterium wr101 reduced nematode disease indices compared to non-treated controls. Inoculation of cucumber roots with B. megaterium wr101 increased peroxidase and polyphenol oxidase activities in root tissue from the first day after inoculation (DAI), with maximum levels of these enzymes recorded 4 DAI and then reduced gradually. Catalase activity and H2O2 accumulation showed two peaks on 1 and 5 DAI, respectively, but the presence of nematodes in the plant significantly increased the activity level of catalase enzyme even in the presence of the bacterium. Bacillus megaterium wr101 also stimulated the accumulation of total phenolic compounds in cucumber roots.