Some notes on the occurrence of plant parasitic nematodes of fruit trees in Slovakia

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Plant Health and Rhizosphere Microbiome: Effects of the Bionematicide Aphanocladium album in Tomato Plants Infested by Meloidogyne javanica

The artificial introduction in the soil of antagonistic microorganisms can be a successful strategy, alternative to agrochemicals, for the control of the root-knot nematodes (Meloidogyne spp.) and for preserving plant health. On the other hand, plant roots and the associated rhizosphere constitute a complex system in which the contribution of microbial community is fundamental to plant health and development, since microbes may convert organic and inorganic substances into available plant nutrients. In the present study, the potential nematicidal activity of the biopesticide Aphanocladium album (A. album strain MX-95) against the root-knot nematode Meloidogyne javanica in infected tomato plants was investigated. Specifically, the effect of the A. album treatment on plant fitness was evaluated observing the plant morphological traits and also considering the nematode propagation parameters, the A. album MX-95 vitality and population density. In addition, the treatment effects on the rhizosphere microbiome were analysed by a metabarcoding procedure. Treatments with A. album isolate MX-95 significantly decreased root gall severity index and soil nematode population. The treatment also resulted in increased rhizosphere microbial populations. A. album MX-95 can be favourably considered as a new bionematicide to control M. javanica infestation

Bacteria as Biocontrol Tool against Phytoparasitic Nematodes

Phytoparasitic nematodes cause severe damage and yield losses to numerous agricultural crops. Considering the revision of the EU legislation on the use of pesticides on agricultural crops, control strategies with low environmental impact are required. The approach based on the use of bacteria seems particularly promising as it also helps to reduce the applied amounts of chemicals and stabilize ecological changes. This paper gives an overview of the main types of bacteria that can be used as biological control agents against plant parasitic nematodes and their interrelationships with plants and other organisms. Many experiments have given positive results of phytoparasitic nematode control by bacteria, showing possible prospects for their application. In vitro, greenhouse and field experiments have shown that bacteria can regulate the development of ecto- and endoparasitic nematodes by different modes of action. Triggering the induction of plant defense mechanisms by bacteria is seen as the optimum tool because the efficacy of bacterial treatment can be higher than that of chemical pesticides or at least close to it. Moreover, bacterial application produces additional positive effects on growth stimulation, raises yields and suppresses other pathogenic microorganisms. Commercial formulations, both as single bacterial strains and bacterial complexes, are examined

Untargeted Metabolomics of Tomato Plants after Root-Knot Nematode Infestation

After 2 months from the infestation of tomato plants with the root-knot nematode (RKN) Meloidogyne incognita, we performed a gas chromatography-mass spectrometry untargeted fingerprint analysis for the identification of characteristic metabolites and biomarkers. Principal component analysis, and orthogonal projections to latent structures discriminant analysis suggested dramatic local changes of the plant metabolome. In the case of tomato leaves, β-alanine, phenylalanine, and melibiose were induced in response to RKN stimuli, while ribose, glycerol, myristic acid, and palmitic acid were reduced. For tomato stems, upregulated metabolites were ribose, sucrose, fructose, and glucose, while fumaric acid and glycine were downregulated. The variation in molecular strategies to the infestation of RKNs may play an important role in how Solanum lycopersicum and other plants adapt to nematode parasitic stress

Soil Phytoparasitic Nematodes Suppression and Changes of Chemical Properties Determined by Waste Residues from Olive Oil Extraction

Abstract: The effect of olive mill wastes soil amendments on phytoparasitic nematodes and on soil fertility was investigated in a field experiment in southern Italy (Apulia region). Fresh and composted olive pomace were distributed at 10 t/ha, 20 t/ha, 40 t/ha rates and raw sewage was supplied at 40 m 3 /ha, 80 m 3 /ha, 160 m 3 /ha, 240 m 3 /ha in a sandy soil (Castellaneta, province of Taranto) infested by Meloidogyne incognita. Untreated and 300 kg/ha granular fenamiphos treated soil were also used as control. Cantaloupe crop yield, soil nematode population and root infestation index were recorded. Soil fertility parameters, C and N contents, nitrates and ammonium, total organic, extracted and humified C, were also determined. The results obtained may suggest that incorporation of OWW into the soil results in a suppression of soil nematode populations and, at low initial soil infestation, also in a crop yield increase. On the other hand the soil system is positively affected by the increase of soil organic matter content; perhaps the incorporation into the soil of organic substances containing, as average, 40 % of C, can contribute to C sequestration and to reduce greenhouse effect

Haloacetophenones as newly potent nematicides against Meloidogyne incognita

Acetophenones are a class of aromatic compounds frequently produced by plants as a response to a stress or as a protection reaction against parasites or herbivors. In the present research, we investigated the role of the carbonyl moiety in a series of commercially available aromatic ketones tested for their nematicidal activity against the root-knot nematode Meloidogyne incognita (Kofoid et White) Chitwood. Interestingly, we found that the presence of electron withdrawing groups onto the aromatic ring were highly efficient in inducing nematode paralysis and death (EC50/24h between 2.5 and 54.8mg/L and EC50/72h between 2.3 and 65.6mg/L, respectively). Moreover, a chlorine atom in α-position to the carbonyl functionality emerged as a key residue in improving acetophenones activity. In this paper, the nematicidal ability of a series of differently substituted acetophenones is reported and the preliminary structure-activity relationship studies are also discussed. We also performed an in vitro GC-MS metabolomics analysis on the potato cyst nematode Globodera pallida, after treatment with 2,4'-dichloroacetophenone (6) at 100mg/L for 24h. The 1-dodecanol and talose were evidenced as the main upregulated metabolites, suggesting a possible V-ATPase dysfunction

Pathogenicity and Host-Parasite Relationships of Heterodera cruciferae in Cabbage

Stunted cabbage ("eLupini") associated with severe soil infestations by a cyst-forming nematode were observed in large patches of open fields in Castellaneta, province of Taranto, southern Italy. Morphological traits based on mature cysts, males, and second-stage juveniles (J2s) and molecular analysis of ribosomal DNA (D2 to D3 expansion segments of 28S and internal transcribed spacer [ITS]1 region) were used to identify the species. ITS1 sequence information supported the identity of Heterodera cruciferae, also showing a high degree of similarity to other species of the Heterodera Goettingiana group, including H. goettingiana, H. carotae, and H. urticae. Nematodes successfully established permanent feeding sites in cabbage roots which caused cellular alterations in the root cortex, endodermis, pericycle, and vascular cylinder by inducing typical multinucleate syncytia. Syncytial cytoplasm was granular and dense, with variously sized vacuoles and hypertrophied nuclei with nucleoli. Cabbage plant growth was also reduced in pathogenicity tests. The relationship between the initial nematode population density in soil and shoot plant weight was well described by the Seinhorst¿fs equation. Tolerance limits with respect to shoot plant weight of cabbage to H. cruciferae was estimated as 1.50 units of eggs plus J2s/cm3 of soil. The minimum relative value (m) for plant height was 0.71 at an initial nematode population density of (Pi) . 64 units of eggs plus J2s/cm3 of soil. The maximum nematode reproduction rate (Pf/Pi) was 4.6 times that of the initial population density of 8 units of eggs plus J2s/cm3 of soil.Peer Reviewe

Electron-Deficient Alkynes as Powerful Tools against Root-Knot Nematode Melodogyne incognita: Nematicidal Activity and Investigation on the Mode of Action

The present study reports on the powerful nematicidal activity of a series of electron-deficient alkynes against the root-knot nematode Meloidogyne incognita (Kofoid and White) Chitwood. Interestingly, we found that the conjugation of electron-withdrawing carbonyl groups to an alkyne triple bond was extremely proficient in inducing nematode paralysis and death. In particular, dimethylacetylenedicarboxylate (10), 3-butyn-2-one (1), and methyl propiolate (4), with EC50/48 h of 1.54 ± 0.16, 2.38 ± 0.31, and 2.83 ± 0.28 mg/L, respectively, were shown to be the best tested compounds. Earlier studies reported on the ability of alkynoic esters and alkynones to induce a chemoselective cysteine modification of unprotected peptides. Thus, also following our previous findings on the impairment of vacuolar-type proton translocating ATPase functionality by activated carbonyl derivatives, we speculate that the formation of a vinyl sulfide linkage might be responsible for the nematicidal activity of the presented electron-deficient alkynes

Nematicidal activity of some essential plant oils from tropical West Africa

Plant parasitic nematodes are among the most destructive plant pathogens worldwide and their control is very challenging. Plant essential oils (EOs) have showed a great potential in nematode control. In this work, EOs from 10 aromatic plants acclimatized in Togo were assessed in vitro for their nematicidal activity on the root-knot nematode Meloidogyne incognita. EOs were subsequently analyzed by GC-MS and compounds were tested individually on nematodes. The most potent EOs were: Ocimum sanctum L., Cymbopogon schoenanthus (L.) Spreng and Cinnamomum zeylanicum Blume with EC 50/72h values of 282 ± 53, 288 ± 30 and 355 ± 126 mg/L, respectively. The EC 50/48h values of tested compounds were 81 ± 14, 117 ± 33, 128 ± 42, 141 ± 47, 168 ± 40, 216 ± 86 and 235 ± 43 mg/L for cinnamyl acetate, methyl eugenol, cinnamyl alcohol, acetyl eugenol, isoeugenol, eugenol and benzyl benzoate, respectively. Furthermore, we found a synergistic nematicidal activity when we combined phenylpropanoids compounds with carvone. EOs and their constituents described herein merit further studies, especially in pot experiments before serving as nematicides