Polissacarídeos de Pycnoporus sanguineus para indução de resistência em tomateiro contra Meloidogyne javanica

Abstract

Plant-parasitic nematodes, such as Meloidogyne spp., have limited tomato crop productivity. Some studies suggest the use of basidiomycete fungi, such as Pycnoporus sanguineus, as an alternative for nematode management. Thus, this study aimed to evaluate the potential of P. sanguineus polysaccharides (PPS) in inducing resistance in tomato plants against M. javanica. The study was conducted in three trials. In the initial trial, the most effective concentration for nematode control was determined, using six PPS concentrations (0, 100, 200, 300, 400, and 500 mg L⁻¹), and evaluating the number of galls and egg mass, egg viability, number of eggs and second-stage juveniles (J2) in the soil and roots, and the reproduction factor. With the PPS concentration established in the first trial, the second trial aimed to determine the best method of PPS application. Based on the results of the first and second experiments, the third experiment used only the treatments most effective in controlling nematodes and examined the defense mechanisms involved in the induction of resistance: total phenolic compound content, the production of reactive oxygen species such as hydrogen peroxide (H₂O₂) and the superoxide anion (O₂⁻), and the activity of the enzymes phenylalanine ammonia-lyase, polyphenol oxidase, peroxidase, ascorbate peroxidase, catalase, and superoxide dismutase. These latter assessments were conducted based on root sample collection at different time points following PPS application (zero (day of treatment), 3 (day of inoculation), 7, 11, 15, 19, and 23 days). The concentration with the highest control level was 500 mg L⁻¹, with reductions of up to 70% in eggs+J2 in the roots. Regarding application methods, the greatest control of nematodes occurred through spraying PPS on the aboveground parts of the plants, with reductions of 66% in eggs+J2 in the soil. Histological and biochemical analyses revealed increased cell wall thickness, which was linked to higher deposition of phenolic compounds and lignin, along with increases in polyphenol oxidase activity, indicating an induced defense response that acted primarily on the maintenance of nematode feeding sites. It is concluded that polysaccharides from P. sanguineus act as resistance inducers in tomato plants, reducing populations of the nematode M. javanica.