Northern Root-knot Nematode Meloidogyne Hapla Research Articles

Wild strawberry Fragaria vesca as potential source for phytonematode resistance

AbstractPhytonematode infections are a major constraint to agriculture and can cause pre-harvest losses of up to one-third of the crop in affected fields. With increasing restrictions on the use of chemical pesticides due to environmental and human hazards, and increasing nematode pressure due to climate change, soil degradation and agricultural intensification, more sustainable ways to manage such plant pests are needed to meet the growing demand for food. Therefore, the reproduction of thermophilic Meloidogyne spp. was evaluated in comparison with that of the northern root-knot nematode Meloidogyne hapla on the wild strawberry Fragaria vesca vs. semperflorens cv. Alexandria, a potential source of resistance to nematode infection. M. hapla showed a high reproductive rate in F. vesca, while the thermophilic Meloidogyne species tested showed significant lower reproductive rates. This suggests that F. vesca vs. semperflorens cv. Alexandria, although not resistant to the nematode species tested, could be used in a management system to down-regulate nematode pressure. In addition, this study helps to reinforce the importance of crop wild relatives in the search for resistance traits to support a more sustainable agriculture.

Northern root-knot nematode Meloidogyne hapla Chitwood, 1949 infecting Kiwi fruit (Actinidia chinensis) in Bageshwar district of Uttarakhand state

Northern root-knot nematode Meloidogyne hapla Chitwood, 1949 infecting Kiwi fruit (Actinidia chinensis) in Bageshwar district of Uttarakhand state

Mutation-driven evolution of antibacterial function in an ancestral antifungal scaffold: Significance for peptide engineering.

Mutation-driven evolution of novel function on an old gene has been documented in many development- and adaptive immunity-related genes but is poorly understood in immune effector molecules. Drosomycin-type antifungal peptides (DTAFPs) are a family of defensin-type effectors found in plants and ecdysozoans. Their primitive function was to control fungal infection and then co-opted for fighting against bacterial infection in plants, insects, and nematodes. This provides a model to study the structural and evolutionary mechanisms behind such functional diversification. In the present study, we determined the solution structure of mehamycin, a DTAFP from the Northern root-knot nematode Meloidogyne hapla with antibacterial activity and an 18-mer insert, and studied the mutational effect through using a mutant with the insert deleted. Mehamycin adopts an expected cysteine-stabilized α-helix and β-sheet fold in its core scaffold and the inserted region, called single Disulfide Bridge-linked Domain (abbreviated as sDBD), forms an extended loop protruding from the scaffold. The latter folds into an amphipathic architecture stabilized by one disulfide bridge, which likely confers mehamycin a bacterial membrane permeability. Deletion of the sDBD remarkably decreased the ability but accompanying an increase in thermostability, indicative of a structure-function trade-off in the mehamycin evolution. Allosteric analysis revealed an interior interaction between the two domains, which might promote point mutations at some key sites of the core domain and ultimately give rise to the emergence of antibacterial function. Our work may be valuable in guiding protein engineering of mehamycin to improve its activity and stability.

How Low Can They Go? Plant-Parasitic Nematode Distribution in a Washington Vineyard

Summary Goals: To map the distribution of two plant-parasitic nematode species, the northern root-knot nematode Meloidogyne hapla and the dagger nematode Xiphinema spp., in a Washington State winegrape vineyard slated for replanting. These nematode species can reduce vineyard longevity and weaken or kill young vines. Knowing how these nematodes are spatially distributed in soil can improve implementation of management strategies. Key Findings: Northern root-knot nematode and dagger nematode had distinctly different distributions within the soil profile. Northern root-knot nematode was concentrated near the vine rows and drip-irrigation lines, in the upper 61 cm (24 inches) of the soil profile. This is reflective of its life strategy, in which association with fine roots and areas of moisture is essential. Dagger nematode was relatively evenly distributed at all distances from the vine row, and significant populations were found down to the deepest sampling depth of 122 cm (48 inches). This demonstrates that it can survive readily on hosts other than grape and can parasitize root types that are not parasitized by northern root-knot nematode. Impact and Significance: This work provides evidence for how and why nematode management practices may differ in their efficacy. Dagger nematodes were distributed throughout the sampled area and were found at depths that most fumigation efforts cannot reach. This increases the likelihood that dagger nematodes will recolonize treated areas, but this may take time as they move upward from deep in the soil. Root-knot nematodes may be more easily controlled via chemigation or fumigation, as their distribution corresponds to shallower areas with high fine root biomass wetted by drip irrigation.

Characterization of bi-domain drosomycin-type antifungal peptides in nematodes: An example of convergent evolution

Drosomycin-type antifungal peptides (DTAFPs) are natural effectors of the innate immune system, which are restrictedly distributed in plants and ecdysozoans. Mehamycin is a bi-domain DTAFP (abbreviated as bDTAFP) firstly found in the Northern root-knot nematode Meloidogyne hapla. Here, we report its structural and functional features and the evolution of bDTAFPs in nematodes. Different from classical DTAFPs, mehamycin contains an insertion, called single Disulfide Bridge-linked Domain (abbreviated as sDBD), located in a loop region of the drosomycin scaffold. Despite this, recombinant mehamycin likely adopts a similar fold to drosomycin, as revealed by the circular dichroism spectral analysis. Functionally, it showed some weak activity against three species of fungi but relatively stronger activity against seven species of Gram-positive bacteria, indicative of functional diversification between mehamycin and classical DTAFPs. By computational data mining of the nematode databases, we identified polymorphic genes encoding mehamycin and a new multigene family of bDTAFPs (named roremycins) from Rotylenchulus reniformis. A combination of data suggests that the origination of sDBDs from M. hapla and R. reniformis is a consequence of convergent evolution, in which some probably suffered positive selection during evolution. Our study may be valuable in understanding the role of these unique antimicrobial peptides in the innate immunity of nematodes.

Comparison of the development ability of the northern root-knot nematode Meloidogyne hapla Chitwood, 1949 on selected species and varieties of Fabaceae Lindl.

Legumes of the genera Vicia, Pisum, Lupinus, Trifolium, Medicago as well as Onobrychis viciifolia, Lotus corniculatus, Ornithopus sativus, Galega orientalis and Lens culinaris were cultivated in pots filled with soil naturally infected with Meloidogyne hapla, under controlled conditions in a glasshouse. Root galls and adult females with egg masses were observed in root systems of all plant species and cultivars included in the experiment. The most numerous occurrence of root galls was recorded on root tissues of Vicia faba, Pisum sativum, Lupinus luteus (cv. Parys) and Trifolium pratense (cv. Krynia) while adult females with egg masses on roots of Trifolium incarnatum, P. sativum (cv. Hubal), Lupinus albus and both cultivars of Medicago sativa. Approximately from 5 to 57 of eggs and juvenile stages were counted in a single mass. Rośliny bobowate z rodzaju Vicia, Pisum, Lupinus, Trifolium, Medicago oraz Onobrychis viciifolia, Lotus corniculatus, Ornithopus sativus, Galega orientalis i Lens culinaris uprawiano w wazonach z glebą naturalnie zainfekowaną guzakiem północnym, w kontrolowanych warunkach w szklarni. Na korzeniach wszystkich badanych gatunków i odmian roślin obserwowano wyrośla oraz samice ze złożami jajowymi. Wyrośla wystąpiły najliczniej na korzeniach Vicia faba, Pisum sativum, Lupinus luteus (odmiana Parys) oraz Trifolium pratense (odmiana Krynia), a samice ze złożami jajowymi na korzeniach Trifolium incarnatum, Pisum sativum (odmiana Hubal), Lupinus albus oraz obu odmianach Medicago sativa. Zliczono średnio od 5 do 57 sztuk jaj i osobników młodocianych przypadających na pojedyncze złoże.

Nematode resistance of rape-radish chromosome addition lines

Abstract Oilseed radish is resistant to the beet cyst nematode (Heterodera schachtii Schmidt), interrupting the life cycle of this sedentary pathogen by blocking feeding cell development in the root. A complete set of nine disomic rape-radish chromosome additions, a to i, derived from a susceptible rapeseed parent as recipient and a resistant radish as chromosome donor, was assayed for nematode resistance. The addition line d exhibited the resistance level of the radish parent, confirming previous results that radish chromosome d carries a dominant gene, Hs1Rph, for nematode resistance. It was investigated if Hs1Rph is effective against a further important sedentary parasite, the northern root-knot nematode Meloidogyne hapla. The set of chromosome addition lines and the parents, rape and radish, were inoculated with second-stage juveniles (J2) of M. hapla and the plant reaction was evaluated by counting the number of egg masses per root system. By contrast to the situation in H. schachtii, the radish parent as well as addition line d showed no resistance against M. hapla and was even more susceptible than rape. It was concluded that the resistance gene Hs1Rph, which inhibits syncytium development of H. schachtii, is ineffective against M. hapla, a nematode inducing giant cell formation. Most added radish chromosomes significantly changed the number of egg masses in the recipient rape towards higher susceptibility. Two chromosomes enhanced the egg mass number beyond that of the chromosome donor radish. However, one radish chromosome decreased the egg mass production in the corresponding addition line below that in rape. This wide range of effects of the individual radish chromosomes in the rape background indicates a quantitative inheritance of host suitability to M. hapla and a complex interaction between the pathogen and radish.

Evaluation of Paecilomyces lilacinus strain 251 for the biological control of the northern root-knot nematode Meloidogyne hapla Chitwood

Abstract The egg-pathogenic fungus Paecilomyces lilacinus strain 251 (PL215) was investigated under different temperature regimes for biocontrol activity against the northern root-knot nematode Meloidogyne hapla. Biocontrol activity by PL251 was affected by temperature and initial nematode inoculum density. At 20/23°C (night/day) control efficacy reached 71% at a high inoculum density of 10 000 eggs and juveniles (E + J) per 500 cm3 compared to 65% control at the lower inoculum density (5000 E + J/500 cm3). By contrast, average efficacy was 5% and 46% at low and high inoculum levels, respectively, when temperatures were between 19°C and 21°C (night/day). A significant interaction between the factors inoculum density and treatment with PL251 was observed at low temperatures, when only few M. hapla galls and egg masses developed after inoculation with 5000 E + J/500 cm3. When the temperature was favourable for the fungal parasite (25°C), efficacy reached 90%. In glasshouse experiments with unfavourable temperatures for M. hapla development (25°C-33°C), tomato plants repeatedly treated with PL251 showed significantly higher fruit yield (23-102%).

Seasonal and vertical distribution of Meloidogyne hapla in organic soil

The seasonal population fluctuations of the northern root-knot nematode Meloidogyne hapla on car rot (Daucus carota), onion (Allium cepa), and weeds were observed on organic soils in southwestern Quebec. Lowest population densities of M. hapla juveniles (J2) were recorded in July and August, followed by a peak in September and October in plots with carrot or weedy fallow. In onion, J2 densities remained near or below the detectable level during most of the sampling period, but a small trend in population increase was also detected in the fall. The vertical distribution of M. hapla was similar in carrot weedy fallow, and onion plots. J2 were regularly recovered from the four sampling depths (0-10,11-20, 21-30, and 31-40 cm). The numbers of J2 were greater in the 0-20 cm depth than the 21-40 cm depth, with 67, 68, and 60% of the total M. hapla population in the 0-20 strata for carrot, weedy fallow, and onion, respectively. The tomato bioassay method was more sensitive than the Baermann pan method for detecting low M. hapla densities. Because of the poor correlation between J2 densities in the soil and the number of galls on tomato roots in the bioassay, a measurement of J2 abundance such as the Baermann pan method shoud be supported by bioassay to further assist growers in their decision process for the management of M. hapla in organic soil.

Effects of crop rotations on carrot yield and on the nematodes Pratylenchus penetrans and Meloidogyne hapla

Carrot yield (Daucus carota) and population levels of the root-lesion nematode Pratylenchus penetrans and the northern root-knot nematode Meloidogyne hapla were measured in five rotation crops and in subsequent carrot crops at three field sites (1998-1999, 1999-2000, and 2000-2001). Total and marketable carrot yields averaged over the three sites did not differ in the crop sequences but there was a difference among sites. The total yields at sites 1, 2, and 3 were 77.86, 68.12, and 30.33 tonnes ha-1, respectively. Marketable yields were 59.04, 60.62, and 24.11 tonnes ha-1 at sites 1, 2, and 3, respectively. The lower yields were attributed primarily to less rainfall during July and August in 2001, and possibly to northern root-knot nematodes that were more prevalent at site 3. Mean levels of root-lesion nematodes in soil were highest (2690 nematodes kg-1) in carrot that followed timothy (Phleum pratense cv. Common), lowest (1100 nematodes kg-1) in carrots that followed marigold (Tagetes erecta cv. Crackerjack), and intermediate after barley (Hordeum vulgare cv. Chapais), pearl millet (Pennisetum glaucum cv. Millet 101), and annual ryegrass (Lolium multiflorum cv. Lemtal). Root-lesion nematode populations were also lower in marigold than in the other crops. Northern root-knot nematodes were not detected in rotation crops. The study indicated that carrot yields did not differ irrespective of the previous crop, but root-lesion nematode populations in soil at harvest were highest in carrots that followed timothy and lowest in carrots that followed marigolds. Population levels of root-knot nematodes in carrots did not differ among the crop sequences.

WINTER SURVIVAL OF ROOT-KNOT NEMATODES (MELOIDOGYNE INCOGNITA AND M. HAPLA) UNDER SELECTED HOST CROPS IN SOUTHERN ONTARIO

In field experiments at Harrow, Ontario, the southern root-knot nematode Meloidogyne incognita overwintered successfully on woody perennial roots of peach in a moderate winter, but was unable to survive a subsequent severe winter on this host. At Vineland Station, Ontario, M. incognita did not overwinter below the frost line in a moderate winter under alfalfa, a poor perennial host, but did overwinter under red clover and tomato in a severe winter, although the population was severely reduced. By comparison, the northern root-knot nematode Meloidogyne hapla survived well under all three hosts in both winters at depths from 0 to 90 cm.

YIELD LOSSES AMONG FORAGE LEGUMES INFECTED WITH MELOIDOGYNE HAPLA

Losses caused by the northern root-knot nematode Meloidogyne hapla in alfalfa, birdsfoot trefoil, and red and white clovers were assessed in microplots over 21/2 yr. Losses were the result of failure of seedling establishment, and reduction in weight of individual plants. Dry matter was reduced in relation to the nematode inoculum density. Plant stand of all four legumes declined up to the second spring after seeding, particularly in infested plots.