The suppression intensity of tomato defence responses by Meloidogyne javanica depends on their detrimental effects on the nematode

Abstract

The aim of this study was to compare the suppressive effects of the root-knot nematode, Meloidogyne javanica , on several key defence-related enzymes, including chitinase, β -1,3-glucanase, protease and phenylalanine ammonia-lyase, as well as the accumulation of hydrogen peroxide (H 2 O 2 ) and total phenolic compounds in tomato plants following nematode inoculation, especially the feeding relationship with the host (1-9 days after inoculation). The results show that M. javanica generally suppressed all defence compounds evaluated in this study, especially during the feeding relationship with the plant; however, the intensity of suppression was more pronounced for those defence elements that are specifically more detrimental to the nematode, namely proteases, phenylalanine ammonia-lyase, H 2 O 2 and total phenols. Furthermore, the results show that this nematode is even able significantly to suppress the accumulation or activity of defence responses pre-induced by elicitors. Based on this, it is proposed that these nematodes exert two types of suppression on plant defence responses: suppression of most or all defence compounds, potentially resulting from interference with their activation or synthesis pathways and a second type of suppression targeting compounds that have detrimental effects on the nematode.