Effects of Jasmonate-Induced Defenses on Root-Knot Nematode Infection of Resistant and Susceptible Tomato Cultivars

Abstract

Jasmonates, such as jasmonic acid (JA), are plant-signaling compounds that trigger induced resistance against certain pathogens and a broad range of arthropod herbivores. One goal of this study was to determine the effects of JA-dependent defenses in tomato on root-knot nematodes. Another was to determine if the artificial induction of these defenses could enhance nematode control on plants that carry Mi-1.2, a nematode resistance gene that is present in many tomato cultivars. At moderate soil temperatures, Mi-1.2 can effectively suppress reproduction of most isolates of the common root-knot nematode species Meloidogyne javanica, M. incognita, and M. arenaria. Mi-mediated resistance has its limitations, however. Mi-1.2 is reported to lose its effectiveness at soil temperatures above 28 degrees C, and certain virulent nematode isolates can overcome resistance even at moderate soil temperatures. This study used a foliar application of JA to activate induced resistance in two near-isogenic lines of tomato (Lycopersicon esculentum) with and without Mi-1.2, and evaluated the effects of induced resistance at moderate soil temperatures on one avirulent nematode isolate (M. javanica isolate VW4) and two virulent isolates (M. javanica isolate VW5 and M. incognita isolate 557R). In addition, the effects of induced resistance on avirulent nematode performance were examined at a high temperature (32 degrees C). The results indicate that JA application induces a systemic defense response that reduces avirulent nematode reproduction on susceptible tomato plants. Furthermore, JA-dependent defenses proved to be heat-stable, whereas the effects of Mi-mediated resistance were reduced but not eliminated at 32 degrees C. JA treatment enhanced Mi-mediated resistance at high temperature, but did not suppress either of the virulent nematode isolates tested.

Jasmonate Biosynthesis, Perception and Function in Plant Development and Stress Responses

“…JA enhances Mi-mediated resistance (Mi is a resistant gene in tomato) of resistant lines at high temperature (Cooper et al, 2005). However, using JA-signaling mutant jar1 (equal to coi1 of Arabidopsis) and JA biosynthesis mutant def1, it was found that endogenous JA signaling pathway is required for tomato susceptibility to RKNs (Bhattarai et al, 2008).…”

The effects of β-amino-butyric acid on resistance of cucumber against root-knot nematode, Meloidogyne javanica

“…Their study also shows a significant increase in activity of phenylalanine ammonia lyase and pathogenesisrelated protein-1 (PR-1) accumulation in roots. Cooper et al (2005), however, have indicated that application of jasmonic acid as a plant-signaling compound to tomato foliage induces systemic effects on root-knot nematode and causes significant reduction in nematode egg masses/g root tissue. They believe that the mechanism through which JA suppresses nematode infestation is ought to be transported from foliage to roots.…”

Not to be suppressed? Rethinking the host response at a root-parasite interface

“…However, foliar pre-treatment of rice and tomato plants with salicylic acid analogs only slightly reduced susceptibility suggesting that the salicylate-mediated signaling may not have a major influence on root-knot nematode infestation of susceptible plants [25,33,34]. Conversely, foliar pre-treatments with jasmonates markedly reduced root-knot nematode infestation in both tomato and rice [25,35,36]. This negative influence of the jasmonate pathway stimulation prior to root-knot nematode infestation could potentially be consistent with a requirement for root-knot nematodes to suppress or avoid activation of the jasmonate defense signaling pathway for successful parasitism of host plants.…”