Characterization of native root-knot nematode antagonistic rhizobacteria for plant growth promotion traits and their evaluation in tomato

Abstract

In the present study, native root-knot nematode antagonistic rhizobacteria i.e., Microbacterium laevaniformansMlIRh3, Staphylococcus kloosiiSkIRh4, and Priestia aryabhattai PaIRh7 from Meloidogyne incognita infected and Staphylococcus sciuri SsHRh3, Bacillus pumilus BpHRh5, Priestia megaterium PmHRh10 from uninfected tomato plants grown in the protected structure were characterized for their key plant growth promotion traits and survivability in soil, viz. phosphate solubilization activity, indole acetic acid production, ammonia production, and substrate utilization profiles. Among rhizobacteria, S. sciuri SsHRh3, B. pumilus BpHRh5, P. megaterium PmHRh10, M. laevaniformans MlIRh3, and S. kloosii SkIRh4 showed phosphate solubilisation activities on Pikovaskaya’s media. In the presence of tryptophan, the rhizobacteria P. megaterium PmHRh10, M. laevaniformans MlIRh3, and P. aryabhattai PaIRh7 produced indole acetic acid. Similarly, S. sciuri SsHRh3, B. pumilus BpHRh5, P. megaterium PmHRh10, S. kloosii SkIRh4, and P. aryabhattai PaIRh7 produced ammonia under laboratory conditions. Among the 35 substrates studied, rhizobacteria had different substrate utilization profiles,S. sciuri SsHRh3 utilized most of the substrates (18), followed by P. aryabhattai PaIRh7, S. kloosiiSkIRh4, M. laevaniformansMlIRh3, B. pumilus BpHRh5 and P. megaterium PmHRh10which were able to use 17, 16, 15, 14 and 13 substrates, respectively. Furthermore, the application of these rhizobacterial isolates either singly or in consortia revealed that a consortium of all three rhizobacterial isolates i.e., SsHRh3 + BpHRh5 + PmHRh10 from nematode uninfested rhizosphere shown highest plant growth promotion activity compared untreated control and singly application. In contrast, S. kloosiiSkIRh4 either singly or in consortia, no significant effect on plant growth was observed under the pot experiment. Overall, the study found that root-knot nematode antagonistic rhizobacterial isolates were a promising candidate for plant growth promotion activity. Using them alone or in combination can be a safe alternative to synthetic chemical nematicides for suppression of root-knot nematode incidence in tomatoes grown under protected environments.