The influence of root diffusate, host age and water regimes on hatching of the root-knot nematode, Meloidogyne triticoryzae

Abstract

The root-knot nematode, Meloidogyne triticoryzae, produces three kinds of unhatched second stage juveniles (J2): i) those that hatch freely in water, ii) those that require stimulus from rice root diffusate (RRD), and iii) those that do not hatch even in the presence of RRD. The proportion of these three types varies with generation, with the final generation produced on senescing plants having a large proportion of unhatched J2 of the third type, which is likely to equate with diapause. Dilution of RRD reduced its hatching activity and there is no evidence of the presence of inhibitors in the diffusate. The hatching response of M. triticoryzae may be modified additionally by the growing conditions: submergence of infected plants may have delayed hatch, possibly by causing anoxybiosis in unhatched J2, and thereby delayed the appearance of the second and third generations of the nematodes. Le nématode Meloidogyne triticoryzae produit trois types de juvéniles de 2ème stade (J2) non encore éclos: i) ceux qui éclosent d’eux-même dans l’eau; ii) ceux qui requièrent le stimulus produit par le diffusat radiculaire de riz (RRD); enfin iii) ceux qui n’éclosent pas même en présence de RRD. La proportion de ces trois types varie avec la génération du nématode, la dernière génération, produite sur un hôte sénescent, contenant une grande proportion de J2 non éclos de type 3, ce fait représentant l’équivalent d’une diapause. La dilution du RRD diminue l’éclosion et aucune évidence d’inhibiteurs n’a été relevée dans le diffusat. Chez M. triticoryzae l’éclosion peut de plus être modifiée par les conditions de croissance de l’hôte; ainsi la submersion des plants infestés peut retarder l’éclosion, l’anoxybiose ainsi induite affectant vraisemblablement les J2 non éclos et retardant de ce fait l’apparition des deuxième et troisième générations du nématode.

The effect of temperature on hatch and activity of second-stage juveniles of the root-knot nematode, Meloidogyne minor, an emerging pest in north-west Europe

“…In our study, the low hatch (49%) in October might be interpreted as eggs being in diapause but not having experienced a long enough cold period. However, similar low hatch (47%) was also seen in May, so other factors must be involved, such as age of females, or condition of soil and/or plant (Huang & Pereira, 1994;Gaur et al, 2000;Wesemael et al, 2006). The M. minor eggs remaining once hatch had ceased appeared to be degenerating, but we cannot be certain that there were no viable eggs amongst them.…”

Toward Chemical Ecology of Plant-Parasitic Nematodes: Kairomones, Pheromones, and Other Behaviorally Active Chemical Compounds

“…For example, the rice root-knot nematode, Meloidogyne triticoryzae Gaur et al, 1993, and the sorghum cyst nematode, H. sorghi Jain et al, 1982, produce three types of eggs: those that hatch spontaneously in water, those that require stimulus from root diffusate, and those that do not hatch even in the presence of root diffusate. The proportion of these three types changes over the successive generations. , When the host plant is young, M. chitwoodi Golden et al, 1980, second-stage juveniles (J2s) do not require root exudate for hatching, whereas it is the opposite when the host plant is old …”

“…The proportion of these three types changes over the successive generations. 31,32 When the host plant is young, M. chitwoodi Golden et al, 1980, second-stage juveniles (J2s) do not require root exudate for hatching, whereas it is the opposite when the host plant is old. 33 Among the compounds already identified as the host plant produced, i.e., kairomonal EHSs, some are volatile, (e.g., C 11 H 16 O 4 or C 13 H 12 O 3 , Table 1) and can be taken from the plant to the nematode cyst though the air (even within the soil).…”

Highly Potent Extracts from Pea (Pisum sativum) and Maize (Zea mays) Roots Can Be Used to Induce Quiescence in Entomopathogenic Nematodes

“…Plant parasitic nematodes use constitutively released root exudates to locate their host plant (Curtis et al 2009;Prot 1980;Reynolds et al 2011;Rolfe et al 2000). Root exudates also are known to trigger egg hatching in several plant-parasitic nematodes (Den Nijs and Lock 1992;Gaur et al 2000;Khokon et al 2009). Zhao et al (2000) were the first to observe the intriguing phenomenon that root cap exudates induce a state of dormancy (quiescence) in a plant-parasitic nematode (Meloidogyne incognita), and they proposed it to be a defense mechanism against root tip penetration.…”