Biocontrol of Meloidogyne incognita by Bacillus velezensis TA-1 through induction of host resistance in tomato.

Meloidogyne incognita is among the most detrimental parasitic nematodes with a wide host range causing huge economic losses annually. Biological control of M. incognita has emerged as a promising alternative in sustainable agriculture. In our previous study, Bacillus velezensis TA-1 effectively controlled M. incognita in vitro and in the field trials through direct nematocidal activities. However, it remains poorly understood for the underlying mechanisms including whether TA-1 could induce host resistance against M. incognita. In the present study, the effects of TA-1 induced resistance against M. incognita in tomato were determined. Results showed that TA-1 colonized tomato roots, with 1.23 × 108 colony forming units (CFU)/g root tissues attached within 36 h, significantly reduced the number of galls in the local and systemic root systems in the split-root experiments by 44.0% and 28.1%, respectively. The bacteria also increased the basic defense responses of tomato plants, such as lignin accumulation and hydrogen peroxide (H2O2) content, which was associated with the enhanced activities of enzymes related to plant defense [e.g. phenylalanine ammonia-lyase (PAL), peroxidase (POD) and polyphenol oxidase (PPO)]. Moreover, TA-1 enhanced the expressions of tomato defense response genes in the salicylic acid (PR1a and PR-P6) and jasmonic acid (PI II and MC) pathways and induced resistance against M. incognita. These results suggested that TA-1 could effectively control M. incognita through induction of tomato resistance, therefore it could be used as a promising biocontrol agent to be incorporated in the integrated management programs in tomato production. [ABSTRACT FROM AUTHOR]