Migratory Endoparasitic Nematodes Research Articles

Effects of an arbuscular mycorrhizal fungus and two plant-parasitic nematodes on Musa genotypes differing in root morphology

In this study, the effect of an arbuscular mycorrhizal fungus (AMF) and two migratory endoparasitic nematodes on Musa plant growth, including the root system, were examined. In addition, the AMF-nematode interaction was studied. Seven Musa genotypes with different root systems were selected. Based on their relative mycorrhizal dependency, two genotypes (Calcutta 4 and Obino l'Ewai) were selected for AMF-nematode interaction studies. The experiments were performed under greenhouse conditions. Mycorrhization with Glomus mosseae resulted in a significantly better plant growth even in the presence of nematodes. The effect of AMF on the root system was genotype-dependent and seemed to be related to the relative mycorrhizal dependency of the genotype. The nematodes also affected the root system, decreasing branching. Nematode population densities were significantly reduced in the presence of AMF, except for Pratylenchus coffeae in Obino l'Ewai. In the root system, it appeared that the decreased branching caused by the nematodes was counterbalanced by the increased branching caused by the AMF.

Relative mycorrhizal dependency and mycorrhiza-nematode interaction in banana cultivars ( Musa spp.) differing in nematode susceptibility

Four Musa cultivars, differing in nematode susceptibility, were selected to study their relative mycorrhizal dependency and to study the interaction between the arbuscular mycorrhizal fungus (AMF), Glomus mosseae, and two migratory endoparasitic nematodes, Radopholus similis and Pratylenchus coffeae. Mycorrhization with G. mosseae resulted in significantly better plant growth, even in the presence of R. similis and P. coffeae. No differences in relative mycorrhizal dependency (RMD) were observed among the four cultivars. G. mosseae suppressed nematode population build-up in Grande Naine and Pisang Jari Buaya. Only in the case of R. similis (Indonesian population) in Pisang Jari Buaya, no significant suppression was observed. In the case of P. coffeae, the AMF reduced the damage in the roots, caused by the nematodes. For R. similis, no reduction of damage was observed. In all, except one experiment, the frequency of the mycorrhizal colonisation was negatively affected by the nematodes.

Molecular phylogenetic analysis and characterization of secretory enzyme genes of the plant parasitic nematodes

This article is an abstract of the paper presented by a winner of the Young Scientist Award at the 2003 Annual Meeting of the Phytopathological Society of Japan in Tokyo Root lesion nematodes, Pratylenchus spp., are cosmopolitan and economically important migratory endoparasitic nematodes. More than 20 Pratylenchus species are found in Japan. The taxonomic distinction of Pratylenchus species is difficult because they have little morphological diversity. Taxonomic difficulties often arise from underestimating the intraspecific variability of certain morphological characteristics presently used for distinguishing species. The success of management programs depends on rapid, reliable identification of the nematodes. Pratylenchus spp. also have a wide host range and invade roots at any developmental stage. In nearly all cases, parasitism is confined to cortical cells. However, few molecular studies have been conducted on the role of secretory enzymes in the relation between Pratylenchus and plants.

DO ARBUSCULAR MYCORRHIZAL FUNGI ALTER PLANT–PATHOGEN RELATIONS?

Arbuscular mycorrhizal (AM) fungi colonize roots of terrestrial plants and have been hypothesized to reduce susceptibility or to improve the vigor of hosts challenged by root pathogens. Meta-analysis was used to test whether a broad pattern exists in which AM fungi not only enhance plant growth but fundamentally alter plant-pathogen interac- tions. Data were gathered from studies published between 1970 and early 1998. In these studies nonmycorrhizal or mycorrhizal plants were untreated or challenged with root-in- fecting fungal pathogens or nematodes. Effect sizes for AM fungus treatment, pathogen treatment, and their interaction were calculated based on measures of average plant growth, pathogen growth, or AM colonization as reported by authors. AM fungus had a very large positive effect, and pathogens had a very large negative effect on plant growth. However, the interaction of AM fungi and pathogen depended upon the class of pathogen. AM fungi tended to decrease the harmful effects of fungal pathogens but to exacerbate the harmful effects of nematodes. Overall, inoculation with AM fungi had a large negative effect on growth of pathogens, but the outcome for nematodes depended upon mode of feeding. AM fungi harmed sedentary endoparasitic nematodes. AM fungi improved growth of migratory endoparasitic nematodes, but this outcome was not significant in an analysis limited to independent experiments. Reduced growth of pathogens in mycorrhizal plants may indicate increased host resistance. Alternatively, reduced AM colonization in pathogen-treated plants may suggest that root- infecting organisms compete for resources. Some experiments that did not meet criteria for meta-analysis were analyzed with x2 tests by calculating the proportion of experiments in which authors reported a significant pathogen effect in the absence vs. presence of AM fungi. AM fungi did not alter the effect of fungal pathogens but reduced the proportion of experiments in which nematodes de- pressed plant growth in a test limited to independent observations. Comparison of frequency distributions of effect sizes suggests that the difference in results for nematodes in the meta-analysis and the x2 tests stems from differences in the AM fungus-plant-pathogen systems examined in each approach rather than a statistical artifact. AM fungi reduced pathogen growth in -50% of studies included in x2 tests, and this effect was similar for fungal vs. nematode pathogens and sedentary vs. migratory nema- todes. Fungal pathogens reduced AM fungus growth more frequently than did nematodes. Both AM fungi and pathogens suffered reduced growth in 16% of experiments that assessed reciprocal effects. Reciprocal suppression was more common when the pathogen was a fungus, which may indicate that fungal pathogens are more likely than nematodes to compete with AM fungi. Almost all research on the effects of AM fungi on plant-pathogen relations has examined economically important species, in low-phosphorus soil, in greenhouse or microplot culture. Although these analyses revealed general patterns of the effects of AM fungi on plant- pathogen relations, research on a broader range of species over a wider range of environ- mental conditions is required to determine the domain for which these patterns apply.

Host plant response of Eumusa and Australimusa bananas (Musa spp.) to migratory endoparasitic and root-knot nematodes

AbstractTwenty-five banana varieties of section Eumusa (AA-group) and seven of the section Australimusa (Fe'i-group) from Papua New Guinea were evaluated for resistance to Radopholus similis, Pratylenchus coffeae and Meloidogyne spp. The host plant responses were compared with the susceptible reference cvs Grande Naine and Cavendish 901. In vitro propagated plants were transferred to the glasshouse in loamy sand and inoculated with approximately 1000 migratory endoparasitic nematodes at 4 weeks after planting. Reproduction of R. similis and P.coffeae in the roots was determined at 8 or 10 weeks, respectively, after inoculation. Reproduction of Meloidogyne spp. was determined 8 weeks after inoculation with 3300 to 5000 eggs. No resistance to R. similis was found in the diploid varieties. The Fe'i variety Rimina and possibly Menei were resistant to R. similis. All varieties tested were susceptible to P.coffeae and Meloidogyne spp. Tests de résistance de bananiers Eumusa et Australimusa (Musa spp.) envers les nématodes endoparasites migrateurs et galligènes - Vingt-cinq variétés de bananier de la section Eumusa (groupe AA) et sept de la section Australimusa (group Fe'i) provenant de Papouasie-Nouvelle Guinée ont été testées pour leur résistance envers Radopholus similis, Pratylenchus coffeae et Meloidogyne spp. Les résponses de ces variétés ont été comparées à celles des cultivars sensibles de référence Grande Naine et Cavendish 901. Des vitroplants ont été mis en place en serre sur un sol argilo-sableux et inoculés 4 semaines après plantation avec environ 1000 R. similis ou P.coffeae dont la reproduction a été déterminée 8 et 10 semaines, respectivement, après inoculation. La reproduction de Meloidogyne spp. l'a été 8 semaines après inoculation avec 3300 à 5000 oeufs. Aucune résistance à R. similis n'a été observée chez les variétés diploïdes. Les variétés du groupe Fe'i Rimina et Menei se sont montrées résistantes à R. similis, avec un certain doute dans le cas de la dernière. Toutes les variétés testées sont sensibles à P.coffeae et Meloidogyne spp.

Effects of two endoparasitic nematodes ( Pratylenchus coffeae and Meloidogyne konaensis) on ammonium and nitrate uptake by Arabica coffee ( Coffea arabica L.)

Coffee plants ( Coffea arabica L.) infected by two endoparasitic nematodes ( Pratylenchus coffeae and Meloidogyne konaensis) exhibited reduced NO − 3 and NH + 4 uptake rates in short-term solution culture experiments. Infection by the sedentary nematode ( M. konaensis) decreased by half the proportion of fine roots per root system and reduced NO − 3 and NH + 4 uptake rates by 63% and 54%, respectively. The migratory nematodes ( P. coffeae) reduced NO − 3 uptake rate by 56% and NH + 4 uptake rate by 24% without affecting the proportion of fine roots per root system. Such lower NH + 4 and NO − 3 uptake rates in the presence of nematodes are consistent with visual symptoms and foliar analyses indicating N deficiency in long-term field experiments with nematode-infected coffee plants. The nematode parasitic behaviors have a strong incidence on the mechanisms involved in the reduction of N uptake. The sedentary endoparasitic nematode ( M. konaensis) decreased N uptake by a reduction of fine roots caused by gall formation without apparently affecting the uptake capacity of uninvaded fine root regions. The migratory endoparasitic nematode ( P. coffeae) seemed to directly affect the root uptake capacity by damaging root cells during nematode penetration, exploration and feeding.

Interactions between migratory endoparasitic nematodes and arbuscular mycorrhizal fungi in perennial crops: A review

The root-lesion nematodes are important pests attacking stone and pome fruit crops throughout the world. They play an important role in the development of orchard replant problems. Host resistance toPratylenchus vulnus, the nematode of concern in mediterranean environments, has been difficult to find, and even more, to transmit into commercial rootstocks. Alternative management measures using early mycorrhizal infection that would confer protection against the nematode at a stage when plants are most vulnerable are currently being explored. These measures are considered important, taking into account a widespread change towards production systems that use in vitro material propagated in treated substrates free of mycorrhizal and other beneficial microorganisms. The prophylactic effect against root-lesion nematodes would be linked to mycorrhizal dependency of the host plant. Increase in tolerance would seem to be related to mycorrhiza assisted nutrition rather than to a direct suppressive effect of AM over the root-lesion nematode. InCitrus, Prunus, Malus andCydonia rootstocks, the nematode has shown to have a negative effect over AM colonization in the root.

Effect of aldicarb on ectoparasitic and migratory endoparasitic nematodes and on the yields of spring barley

SUMMARYIn six trials in 1971 on two different soils in eastern England, aldicarb at 4.4 kg active ingredient per ha reduced the numbers of Pratylenchus in the roots of spring barley during the season and also the numbers of Pratylenchus and ectoparasitic nematodes in the soil after harvest. Yields of barley were increased in only two of the five trials harvested. P. neglectus (Rensch) Chitwood & Oteifa was the commonest species of Pratylenchus at all six sites, but small numbers of P. penetrans (Cobb) Chitwood & Oteifa were found at three sites and at two of these aldicarb increased yields slightly.