Sequential application of salicylic acid as an inducer of defense systems during a growing season of tomato plants against root-knot nematode

This study evaluated the effectiveness of sequential applications of salicylic acid as an inducer of plant defense responses in tomato against Meloidogyne javanica. The experimental treatments were based on 10-day intervals between consecutive applications of the inducer, and the results were examined in terms of reducing nematode disease indices (mean number of galls and egg masses per plant and mean number of eggs per individual egg mass) and evaluating some defense compounds in the plant. The results showed that sequential use of this inducer at the mentioned time intervals significantly reduced nematode disease indices significantly more than a single application. Evaluation of some plant defense responses, including peroxidase, polyphenol oxidase, phenylalanine ammonia lyase and protease enzymes, as well as the accumulation of hydrogen peroxide and total plant phenols, also showed that tomato plants not only do not lose their responsiveness when the inducer is used repeatedly throughout the growing season, but also induce defense compounds as in the first stimulation, and in all cases with a significant increase. Among the evaluated compounds, the accumulation of phenolic compounds and protease enzyme activity showed a more increasing trend, which can support the potential effectiveness of this strategy. The results indicate that the sequential use of plant defense system inducers during the growing season can be a suitable strategy for more efficient management of plant diseases.