Variation in lipid reserves of second-stage juveniles of Meloidogyne exigua in a coffee field and its relationship with infectivity

Abstract

In this study we assessed the variations in lipid content of second-stage juveniles (J2) of Meloidogyne exigua, recovered from a coffee field, by staining and quantifying the neutral lipids using image analysis. Our results showed that annual variations in J2 stained lipid area correlate with temperature, rainfall and total number of J2 per 100 cm 3 of soil. Laboratory and glasshouse experiments showed that decreases in the lipid stained area of J2 of M. exigua led to decreased infectivity and reproduction on tomato. The susceptibility of tomato cvs Kada and Nemadoro to M. exigua varied according to the stained lipid area of the J2 inoculated on roots. Only J2 containing an average of 80% stained lipid area were able to infect cv. Nemadoro, which contains the Mi resistance gene, whereas J2 containing 20% stained lipid area were still able to infect cv. Kada, considered to be highly susceptible. In this study we show for the first time the dynamics of lipid variation in J2 of M. exigua in a coffee field and the dependence of infectivity and parasitism on the resistance level of tomato cultivars and the lipid stained area in J2.

Velocity of Meloidogyne ethiopica second‐stage juveniles in sandy soil under several soil moisture conditions

“…Most of the evaluated J2 specimens were found at the shortest possible distances (1.5 cm and 4.5 cm), less than the established minimal distances, or not at all, waiting instead for the root to grow nearer. This hypothesis is consistent with the proposal made by Rocha et al (2010) regarding the negative effect of root distance on the migration of juvenile M. incognita. A preference for waiting for the roots to move closer would also be linked to increased water movement, which would require the nematode to move against the flow, thus expending energy reserves.…”

Survival and infectivity of second-stage root-knot nematode Meloidogyne incognita juveniles depend on lysosome-mediated lipolysis

“…Previous studies have shown that lipid contents are correlated with the infectivity of J2 worms ( 11 , 16 , 28 ). As expected, the infectivity of J2 worms on tomato roots was reduced to about 39% and 11% in middle- and last-stage J2 worms, respectively, compared to that of early-stage J2 worms ( Fig.…”

“…Lipid hydrolysis has been commonly observed in J2 of RKNs in the absence of host plants ( 11 , 16 , 28 ). Here, we elucidated the molecular mechanism of lipid hydrolysis, which is required for maintaining fitness of J2 worms when they are outside of host plants ( Fig.…”

“…Based on our observation, the action of ammonia-releasing compounds to control RKNs is mainly attributed to reduce the infectivity of J2 worms by inhibiting lysosomal lipolysis. For J2 worms, synchronization between hatching from eggs and the presence of suitable roots nearby is desirable in the establishment of a successful parasitic relationship ( 16 ). However, hatching of infective J2 worms is often not synchronized with the occurrence of susceptible host roots ( 40 ).…”

“…In addition, the infectivity of Meloidogyne spp. declines significantly with a corresponding decrease of lipid reserve ( 11 , 16 ).…”