Search Results (401)

Today, interest in natural remedies for biocontrol of crop pests is paramount. Punica granatum L. (pomegranate) is studied worldwide to obtain interesting bioactive compounds. Its anti-parasitic activity is associated with the presence of alkaloids in its roots. In this work, we explored the possibility of obtaining from P. granatum roots pelletierine-like alkaloids, which were extracted, characterized, isolated and used for the biocontrol of pests such as Spodoptera littoralis, Myzus persicae, Rhopalosiphum padi and Meloidogyne javanica. Two different extracts were obtained, characterised and quantified by GC-MS and LC-ESI-HRMS. In vitro assays of nematicidal activity were performed comparing the extracts with isopelletierine and pseudopelletierine as pure molecules. The results of these assays showed a difference in activity between iso- and pseudopelletierine, especially in terms of the nematocidal effect against M. javanica with isopelletierine being more active than pseudopelletierine. This leads us to conclude that only extracts from P. granatum roots with a high concentration of isopelletierine alkaloid can be used in effective pest control products. Full article

Pasteuria penetrans (Pp) is a mycelial and endospore-forming bacterium that parasitizes Meloidogyne spp. A single Pp population may contain multiple genotypes that differ in their spore-attachment specificity. Consequently, a subpopulation within a Pp isolate, which can attach to one Meloidogyne species, may fail to attach to another. Repeated culturing of that Pp isolate, on different Meloidogyne species, may therefore lead to shifts in host specificity. We tested this hypothesis using M. luci and M. arenaria, both of which are quite poor hosts of the Pp3 isolate maintained on M. javanica. Using relatively high spore concentrations (10⁶ spores/mL), low levels of attachment and infection were obtained, and after three successive selection cycles, Pp3 sub-isolates adapted to M. luci and M. arenaria were generated. This selection process was associated with a fitness cost, expressed as reduced spore attachment on M. javanica. The shift in host specificity proved reversible. When the adapted Pp3 M. arenaria and Pp3 M. luci sub- isolates were subsequently selected on M. javanica, for two generations, they regained the ability to attach on M. javanica but with a corresponding fitness cost, of spore attachment on M. arenaria and M. luci. These results demonstrate that Pp host specificity is plastic and capable of rapid selection-driven changes in attachment patterns, although such shifts are accompanied by fitness trade-offs. Full article

Root-knot nematodes (Meloidogyne incognita) are among the most destructive pests affecting cucumber production, causing significant reductions in plant growth and yield. This study investigated the efficacy of chitosan-based soil amendments, alone and in combination with hot or cold jojoba (Simmondsia chinensis) leaf extracts and leaf powder, in suppressing nematode infestation and enhancing cucumber vegetative growth under greenhouse conditions. Treatments were evaluated for their impact on nematode reproduction, including egg masses, eggs per egg mass, second-stage juveniles (J2s), female numbers, and gall formation, as well as on plant growth parameters such as height, leaf number, and fresh and dry biomass. Chitosan alone reduced egg masses, eggs per egg mass, and J2s by 43.83%, 56.35%, and 50.63%, respectively, while hot water extract reduced them by 44.10%, 54.18%, and 50.48%. Cold extract was less effective, with reductions of 31.36%, 48.29%, and 40.31%, whereas leaf powder alone caused reductions of 44.20%, 54.60%, and 45.00%. Combined applications exhibited higher efficacy: hot extract + chitosan reduced egg masses, eggs per egg mass, and J2s by 61.64%, 59.45%, and 55.57%, leaf powder + chitosan by 64.38%, 60.70%, and 60.71%, and the triple treatment (leaf powder + chitosan + hot extract) achieved the highest suppression, reducing egg masses, eggs per egg mass, and J2s by 75.90%, 74.66%, and 69.22%, respectively. All treatments significantly enhanced cucumber growth compared with the naturally infested control. The triple treatment increased plant height by 38.5%, leaf number by 42.1%, fresh shoot biomass by 46.3%, and dry shoot biomass by 44.8%. Single treatments also improved growth, though to a lesser extent, reflecting a synergistic effect of chitosan and jojoba-derived amendments. These findings demonstrate that integrating biopolymer-based amendments with plant-derived bioactive compounds can simultaneously suppress root-knot nematode populations and promote cucumber growth. This study provides a solid basis for developing sustainable and eco-friendly integrated pest management strategies that reduce reliance on chemical nematicides. Full article

The natural product composition of the hexane and methyl tert-butyl ether extracts of Dittrichia viscosa roots was examined. Eight terpenoids were identified by nuclear magnetic resonance (NMR) and high resolution mass spectroscometry (HRMS) techniques, four of which (1, 5, 6 and 8) are reported here for the first time as natural products. Of these eight compounds, four are thymol derivatives (1–4), two are guaianolides (5 and 7) and two are himachalanes (6 and 8). Additionally, the occurrence of himachalanes in this species is reported for the first time. Furthermore, a study of the potential plant protection effects of some of these natural products and the chemical derivative 6a was carried out. Promising preliminary results were obtained for compounds 1–3 and 6a as antifeedant agents against Spodoptera littoralis; 1–3 and 5 against Myzus persicae; 1–3 against Rhopalosiphum padi; and 4 as nematicide against Meloidogyne javanica. Finally, the phytotoxic activity of compounds 4, 5 and 6a against the monocotyledonous species Lolium perenne was also proven. Full article

The response of five Passiflora species as rootstocks for yellow passion fruit was evaluated against the Meloidogyne incognita complex and Fusarium oxysporum f. sp. passiflorae. Individual, sequential, and simultaneous inoculations were applied, quantifying disease severity, nematode reproduction (RF), biomass, and plant vigour. In addition, integrated analysis was performed using the Combined Tolerance Index (CTI) to confirm the simultaneous interaction of the inoculation condition. The graft compatibility index (GCI) of the materials under study was also determined. The results showed critical functional differences; P. maliformis showed tolerance in terms of compensatory vigour but presented high susceptibility to the nematode and low graft affinity (GCI = 1.39). In contrast, P. platyloba emerged as the superior genotype, combining effective resistance to Meloidogyne (zero incidence at critical stages), excellent anatomical compatibility (deviation from the ideal of 0.04), and physiological stability superior to the control. Although P. nitida showed resilience in biomass under severe stress conditions, it is concluded that P. platyloba is the most promising alternative for use as rootstock. This is because its morphological affinity and health resistance ensure crop sustainability in field conditions and promote more sustainable agricultural practices. Full article

The ascomycete fungus Clonostachys rosea is a promising biocontrol agent against root-knot nematodes. To develop a more effective and stable biocontrol strategy, we rationally constructed a co-culture system by partnering C. rosea with the plant growth-promoting bacterium Bacillus velezensis. Through systematic optimization of the medium and inoculation protocol, the co-culture demonstrated significantly enhanced performance, achieving 95.3% mortality of Meloidogyne incognita juveniles, a 78.0% increase in tomato shoot dry weight, and 69.2% disease control efficacy in pot trials. Metabolomic profiling indicated that the co-culture triggered a distinct metabolic profile compared to the respective monocultures. The enhanced efficacy was associated with the accumulation of two functional metabolite groups. First, the co-culture synergistically accumulated direct-effect compounds with reported nematicidal (e.g., daidzin, L-tryptophan) and plant-growth-promoting (e.g., isopentenyladenine, melatonin, and indole-3-propionic acid) activities. In parallel, L-proline emerged as a critical microbial interaction modulator. Targeted quantification showed a clear proline abundance gradient: highest in the C. rosea monoculture, intermediate in co-culture, and lowest in the B. velezensis monoculture. This gradient suggests that proline produced by C. rosea is likely utilized by B. velezensis, a finding further supported by the observation that proline enhanced bacterial biofilm formation and upregulated the matrix genes epsC and tasA. Accordingly, the co-culture itself formed significantly more robust biofilms. Thus, the enhanced biocontrol can be attributed to synergistic metabolite accumulation together with proline-mediated fitness gains in the bacterial partner, establishing a metabolic basis for rationally engineering microbial consortia. Full article

Yam end black disease (YEBD) is a devastating soil-borne disease that severely compromises the yield of Chinese yam (Dioscorea opposita Thunb.). Despite its agricultural importance, the etiological agents and molecular mechanisms underlying YEBD remain poorly understood. In this study, we employed an integrated multi-omics approach, combining transcriptomics and microbiome analysis, to dissect the host responses and microbial shifts associated with YEBD. De novo transcriptome assembly revealed significant enrichment of differentially expressed genes involved in polyamine metabolism and hormone signaling pathways. Microbiome profiling identified a substantial increase in nematodes (Meloidogyne spp.) in diseased samples, which correlated negatively with the beneficial fungus Cladosporium. Bacterial community analysis showed an increase in Proteobacteria and Bacteroidetes and a decrease in Actinobacteria and Firmicutes in YEBD-affected roots. Notably, the rhizosphere microbiome was less affected than the endophytic community, suggesting that internal microbial dysbiosis plays a critical role in disease progression. These findings provide new insights into the interactions among yam, nematodes, and microbes, offering potential strategies for biocontrol and disease management. Full article

Plant-parasitic nematodes (PPNs) cause big crop losses globally. Safe/reliable methods for their durable management strategies can harness various beneficial relationships among the plant immune system and related microbiomes. Molecular mechanisms basic to these relations reveal wide arrays of significant roles for plant-healthy growth. This review focuses on such relations of microbiomes to prime and immunize plants against PPNs. It also highlights molecular issues facing PPN-resistant varieties with possible solutions such as genetic breeding/engineering, grafting, PPN-antagonistic root exudates, and novel resistant cultivars. These issues call for optimal uses of various widespread groups of microbiomes. Related plant signaling hormones and transcription factors that regulate gene expression and modulate nematode-responsive genes to ease positive/negative adaptation are presented. Exploring PPN-resistance genes, their activation mechanisms, and signaling networks offers a holistic grasp of plant defense related to biotic/abiotic factors. Such factors relevant to systemic acquired resistance (SAR) via plant–microbe interactions to manage PPNs are stressed. The microbiomes can be added as inoculants and/or steering the indigenous rhizosphere ones. Consequently, SAR is mediated by the accumulation of salicylic acid and the subsequent expression of pathogenesis-related genes. To activate SAR, adequate priming and induction of plant defense against PPNs would rely on closely linked factors. They mainly include the engaged microbiome species/strains, plant genotypes, existing fauna/flora, compatibility with other involved biologicals, and methods/rates of the inoculants. To operationalize improved plant resistance and the microbiome’s usage, novel actionable insights for research and field applications are necessary. Synthesis of adequate screening techniques in plant breeding would better use multiple parameters (molecular and classical ones)-based ratings for PPN-host suitability designation. Sound statistical analyses and interpretation approaches can better identify genotypes with high-level, stable resistance to PPNs than the commonly used ones. Linking molecular mechanisms to consistent field relevance can be progressed via dissemination of many advanced techniques. The CRISPR/Cas9 system has been effective in knocking out both the OsHPP04 gene in rice to confer resistance against Meloidogyne graminicola and the GhiMLO3 gene in cotton to minimize the Rotylenchulus reniformis reproduction. Its genetic modifications in crops synthesized “transgene-free” PPN-resistant plants without decreased growth/yield. Characterizing microbiome species/strains needed to prime and immunize plants requires better molecular tools for fine-scale taxonomic resolution than the common ones used. The former can distinguish closely related ones that exhibit divergent phenotypes for key attributes like stability and production of enzymes and secondary metabolites. As PPN-control strategies via tritrophic interactions are more sensitive to the relevant settings than chemical nematicides, it is suggested herein to test these settings on a case-by-case basis to avoid erratic/contradictory results. Moreover, expanding the use of automated systems to expedite detection/count processes of PPN and related microbes with objectivity/accuracy is discussed. When PPNs and their related microbial distribution patterns were modeled, more aspects of their field distributions were discovered in order to optimize their integrated management. Hence, the feasibility of site-specific microbiome application in PPN–hotspot infections can be evaluated. The main technical challenges and controversies in the field are also addressed herein. Their conceptual revision based on harnessing novel techniques/tools is direly needed for future clear trends. This review also engages raising growers’ awareness to leverage such strategies for enhancing plant resistance and advancing the microbiome role. Microbiomes enjoy wide spectrum efficacy, low fitness cost, and inheritance to next generations in durable agriculture. Full article

Kiwifruit (Actinidia spp.) has become a globally important crop, with A. chinensis var. deliciosa cv. Hayward being the most widely cultivated cultivar. Root-knot nematodes (RKNs, Meloidogyne spp.) are highly damaging plant parasites that are widespread in Portugal. Meloidogyne hapla predominates in the major production areas and occasionally co-occurs with M. arenaria and M. hispanica; however, the effects of these RKNs on kiwifruit performance and yield remain largely unclear. This study evaluated the reaction of Hayward and Tomuri cultivars to different Meloidogyne spp. and inoculum levels, focusing on plant–nematode interactions with distinct M. hapla populations. Kiwifruit’s reaction to RKN parasitism varied according to both the Meloidogyne spp. and the intraspecific variability of M. hapla. Meloidogyne arenaria and M. hispanica caused different impacts in kiwifruit cultivars. Intraspecific variation in M. hapla influenced the host reaction, with certain populations showing high parasitic rates. Gall numbers increased with M. hapla inoculum density, indicating that higher nematode populations intensify pressure on the host. Although few differences were observed between cultivars, M. arenaria had a greater impact on cv. Hayward (female), while M. hispanica affected cv. Tomuri (male) more strongly, showing the importance of investigating cultivar- and sex-specific responses to RKNs for effective management in kiwifruit. These findings highlight that susceptibility and tolerance in kiwifruit depend on the RKN species identity, intraspecific variability, population density and cultivar-specific responses, emphasizing the complexity of host–nematode interactions. Full article

To date, searching for bionematicidals is essential. In the absence of nematicides, “Basic Substances” are gaining ground since they are cost-effective, do not mandate an expiration date and have no inherent capacity to cause endocrine-disrupting neurotoxic or immunotoxic effects. Most “Basic Substances” are authorized for the control of phytoparasitic fungi and insects, whereas nematicidals are yet to be available. In this study, we employed “Basic Substances” and in particular, beer, sodium bicarbonate, and sodium chloride, together with rose aromatotherapy by-products, on nematicidal bioassays against Meloidogyne incognita. We report that chemical composition analysis of the nematicidal rose extracts correlates with bioactivity. Paralysis-based bioassays were used as primary criteria to assess efficacy, specifically targeting second-stage juveniles of Meloidogyne incognita. The evaluated treatments were assessed after one day, two days, and three days of J2 immersion in test solutions. According to our results, the “Basic Substances” demonstrated a significant paralysis effect on J2, thus indicating, for the first time, the considerable significance of their authorization to the root knot nematodes. Similarly, the rose extracts were found to be nematicidal, and since they are foodstuffs, and thus nonconcern compounds, “Basic Substances” can be developed as aromatherapy by-products in the frame of a circular economy. Full article

Kenaf (Hibiscus cannabinus) is a versatile fiber crop known for rapid growth and high biomass productivity that is often cultivated in warm-season regions where root-knot nematodes (RKNs) are prevalent. Here, we compared eight kenaf genotypes with Hibiscus acetosella and Hibiscus sabdariffa to evaluate resistance versus susceptibility to five RKN (Meloidogyne spp.) populations in two replicated greenhouse trials. The nematode panel comprised globally dominant species (M. incognita races 2 and 4, M. javanica) and emerging high-impact threats in warm-season systems (M. floridensis and M. enterolobii), which overlap geographically with current and potential kenaf production. Reproduction and galling were quantified using eggs per system, eggs per gram of root, egg masses, gall index, and reproduction factor, and genotypic differences were assessed by nonparametric rank-based tests at α = 0.05. Across nematode species, H. acetosella and H. sabdariffa showed minimal reproduction and galling, whereas most kenaf genotypes were highly susceptible. Susceptibility was most pronounced to M. enterolobii and M. floridensis, and several kenaf lines (‘Whitten’, ‘G 14’, ‘G 32’, ‘Yue 74-3’) had the highest egg counts and near-maximal egg masses and galling. M. incognita race 2 and race 4 produced strong contrasts, with H. acetosella and H. sabdariffa remaining resistant while multiple kenaf lines exhibited heavy reproduction and severe galling. M. javanica followed a similar pattern, with ‘G 32’, ‘Yue 74-3’, ‘Whitten’, ‘G 14’, and ‘74200 I4’ being highly susceptible. These results identify H. acetosella ‘PI 500707’ and H. sabdariffa ‘X17’ as robust donors of RKN resistance and highlight the susceptibility of cultivated kenaf genotypes, underscoring urgent breeding and integrated management needs for kenaf in warm-season production regions. Full article

Root-knot nematodes (Meloidogyne spp., RKN) penetrate the roots of plants, blocking the flow of water and nutrients, preventing plant development, and causing losses of up to 68% in production. Its management is limited by the low availability of genetically resistant materials, the inefficient use of biological controllers, and the high risk of environmental contamination from the application of pesticides. The aim of this study was to contribute to the integrated management of (RKN) through the use of chitosan. A completely randomized experimental design was used in a factorial arrangement with two applications (foliar or edaphic), two cherry tomato genotypes (IAC1687 and LA2076), and eight treatments (three concentrations of chitosan (1.5–2.0–2.5 mg/mL), commercial controls and absolute controls). The yield and nematode population components were evaluated. The cherry tomato (IAC1687) obtained the greatest yield, with 33.517.1 kg/ha and an 85% reduction in the nematode population with the application of 2.5 mg/mL of chitosan to the soil. Chitosan improved the yield components of the evaluated cultivars and reduced nematode populations, suggesting that it can be a sustainable alternative in commercial production systems, as it can help reduce the use of chemical pesticides and improve health and crop productivity. As a limitation of this study, the use of acetic acid as a solvent for chitosan potentially interfered with the results associated with the nematode population, increasing bias and imprecision as there was no blockage due to light, temperature, or irrigation. Therefore, we suggest that future research explores alternative solvents to elucidate the mechanism of action or response of chitosan. Full article

Early and non-destructive detection of plant-parasitic nematodes is critical for implementing site-specific management in coffee production systems. This study evaluated the potential of unmanned aerial vehicle (UAV) multispectral and thermal imaging, combined with textural analysis, to detect Meloidogyne exigua infestation in Coffea arabica (Topázio variety). Field surveys were conducted in two contrasting seasons (dry and rainy), and nematode incidence was identified and quantified by counting root galls. Vegetation indices (NDVI, GNDVI, NGRDI, NDRE, OSAVI), individual spectral bands, canopy temperature, and Haralick texture features were extracted from UAV-derived imagery and correlated with gall counts. Under the conditions of this experiment, strong correlations were observed between gall number and the red spectral band in both seasons (R > 0.60), while GNDVI (dry season) and NGRDI (rainy season) showed strong negative correlations with gall density. Thermal imaging revealed moderate positive correlations with infestation levels during the dry season, indicating potential for early stress detection when foliar symptoms were absent. Texture metrics from the red and green bands further improved detection capacity, particularly with a 3 × 3 pixel window at 135°. These results demonstrate that UAV-based multispectral and thermal imaging, enhanced by texture analysis, can provide reliable early indicators of nematode infestation in coffee. Full article

Root-knot nematodes (RKN), especially Meloidogyne incognita, threaten global alfalfa crops because of their broad host range and pathogenic nature. Despite its significance, research on resistance is limited. In this study, 24 varieties from China, the US, Canada, Australia, and France were assessed for resistance using the Disease Index (DI) and Egg Mass Index (EMI). Results identified 19 varieties with varying resistance levels and 5 that were susceptible. Chinese Gannong No. 9 was highly resistant (DI: 10) and achieved the highest composite score (91). The US varieties Dryland and Moste were classified as resistant (DI: 14.3% and 12.5%, respectively) and also ranked highly by composite score (65 and 62.5). A moderate correlation between DI and EMI (r = 0.68) led to some inconsistent classifications, including for 2295, Instict, and WL168HQ, highlighting the importance of using multiple complementary metrics for accurate resistance evaluation. Egg mass production was strongly correlated with galling severity (r = 0.70), while root biomass showed no correlation with galling (r = 0.09), indicating root weight is not a reliable resistance indicator. Preliminary infection dynamics showed similar nematode penetration rates at 2 days post-infection across resistant and susceptible varieties. At 7 days post-infection, both resistant and susceptible varieties retained predominantly J2 larvae (78–89%), with no statistically significant differences in developmental stage distributions. These preliminary observations suggest that resistance-associated effects on nematode development, if present, are not strongly expressed at early stages of infection. The mechanistic basis of resistance in alfalfa remains unresolved and warrants further investigation using additional timepoints, histological analyses of feeding-site development, and molecular characterization. Geographically, American varieties displayed broad performance variation, Chinese varieties showed a bimodal distribution, and Canadian varieties exhibited moderate, consistent resistance. These results offer valuable germplasm for breeding and highlight the importance of multiple resistance metrics. Resistant varieties such as Gannong No. 9 provide important genetic resources for developing durable nematode resistance in alfalfa and can guide variety selection in nematode-infested regions. Full article

Root-knot nematodes (RKNs) of the Meloidogyne genus impact various plants, including crops, fruits, and vegetables. Few chemical control options exist globally, and many nematicides are banned due to health and environmental risks. This study tested a new nematicidal agent, the symbiotic bacterium Xenorhabdus indica, which was molecularly identified (PV845100). Cell-free culture supernatants of Xenorhabdus spp. and their biogenic Ag-NPs were used in nematicidal assays. Meloidogyne incognita showed high mortality rates of 95.3%, 74.6%, and 72.6% after 72 h of treatment with the X. indica filtrate at three concentrations. At the same concentrations, biogenic Ag-NPs resulted in 82.0%, 90.0%, and 85.3% mortality rates, respectively. After 72 h, hatchability decreased by 53%, 74.6%, and 72.6% for the X. indica filtrate and 82.0%, 90.0%, and 85.3% for Ag-NPs. Quantitative real-time PCR (Q-PCR) revealed that Mi-Ache1 expression was lower in M. incognita second-stage juveniles (J2s) treated with the filtrate and Ag-NPs after 72 h compared to controls. Mi-Ache2 expression was also decreased, but only slightly. Furthermore, both the X. indica filtrate and biogenic Ag-NPs were safe in human lung (WI-38) and skin (HFB4) cell lines. These findings suggest that bacterial filtrates and their biogenic Ag-NPs could serve as cost-effective, environmentally friendly alternatives to commercial nematicides. Full article