Nematode Populations Research Articles

Efficacy of Noval Nematicide on Root-knot Nematode, Meloidogyne javanica and Establishment of Recommended Dose in Mung Bean (Vigna radiata L.)

The study was carried out to efficacy of newer nematicide (fluensulfone 2% GR) at different doses under field conditions on mung bean. Total seven treatments were used with different doses of fluensulfone 2% GR i.e., T1 - fluensulfone 2% GR 10 kg/ha., T2 - fluensulfone 2% GR 12 kg/ha., T3 - fluensulfone 2% GR 14 kg/ha., T4 - fluensulfone 2% GR 16 kg/ha., T5- fluensulfone 2% GR 18 kg/ha., T6- fluensulfone 2% GR 20 kg/ha., T7 - carbofuran 3G 50 kg/ha and T8 - untreated check (control) maintained for comparison. The observations were recorded on plant growth characters (shoot length (cm), shoot weight (gm), root length (cm), and root weight (gm)) and nematode reproduction (number of galls per plant, number of egg mass per plant, number of eggs per egg mass, nematode juveniles per 200 cc soil and final nematode population). Treated plant with fluensulfone 2% GR with the dose of 20kg/ha found to be the best to given the maximum plant growth characters and minimized nematode reproduction.

Enhancing crop resistance to root nematodes through advanced breeding techniques

This study aimed to evaluate the effectiveness of using nematode-resistant maize and cassava in Nigeria to improve farmers' sustainability and reduce pest pressures. Nematodes significantly impact global crop yield and availability, necessitating the development of resistant cultivars to reduce yield losses and reliance on chemical control measures. Field experiments were conducted in Agbor-Nta, Nigeria, using Resistant Variety A and Resistant Variety D developed from CRISPRCas9 and Marker Assisted Selection. The study found that Resistant Variety A reduced nematode count by 80%, increased yields, and higher net profits. Resistant Variety D also showed reasonable nematode control and economic returns, significantly reducing the nematode population to 12 per gram, achieving a 76% reduction. The adoption rate of CRISPR-Cas9 developed Resistant Variety A reached 50% by 2024. The study underscored the importance of advanced breeding technologies in producing nematode-resistant crops for farming sustainability and economies. The application of germplasm from CRISPR-Cas9 and MAS techniques successfully improved genetic improvement, reduced pest pressures, and enhanced yields. These findings align with efforts to improve agricultural sustainability by promoting reliable crop types to maintain food supply and economic stability in agricultural-dependent areas.

A New Cyst Nematode, Heterodera luodingensis n. sp. (Nematoda: Heteroderinae) From Rice In China.

A unique cyst nematode population (Heterodera spp.) was collected from rice roots in Luoding County, Guangdong Province, China. Morphological and molecular analyses revealed it is significantly different from all previously described cyst nematode species. It is described as Heterodera luodingensis n. sp. and classified in the Cyperi group. H. luodingensis n. sp. is characterized by its lemon-shaped cyst with a prominent terminal vulval cone that is ambifenestrate with abundant bullae and a relatively short vulval slit, 31.3 (24.4 -38.7) μm long. The second-stage juveniles (J2) are characterized by dumbbell shaped labials, three lip annules and a lateral field with three incisures. The J2 stylet is 18.7 (16.9 -19.8) μm long with anterior concave or spherical knobs. The tail is elongate conoid, tapering to a rounded terminus or zig tapering to a rounded terminus that is 54.9 (43.9 - 64.3) μm long with a hyaline region comprising 40.3%-52.5% of the tail. Phylogenetic tree analysis based on rDNA 28S D2D3 and ITS fragments showed that the H. luodingensis n. sp. is unique and clearly separated it from other cyst nematodes. It is most closely related to H. oryzicola, H. fengi, H. elachista, H. oryzae, and H. guangdongensis. H. luodingensis n. sp. can be distinguished from H. oryzicola by its shorter vulval slit and underbridge, from H. elachista by abundant bullae, shorter vulval slit and fenestrate width, from H. oryzae by a shorter vulval slit and underbridge, from H. fengi by a shorter vulval slit, from H. guangdongensis by a longer cyst length and abundant bulla. Based on PCR-RFLP of rDNA-ITS, H. luodingensis n. sp. can be clearly distinguished from H. oryzicola, H. mothi, H. elachista, H. guangdongensis and H. cyperi. A parasitism test from a pure culture derived from a single cyst in greenhouse showed that H. luodingensis n. sp. can successfully complete its life cycle on rice and rice is its type host.

Combining Masculinizing Resistance, Rotation, and Biocontrol to Achieve Durable Suppression of the Potato Pale Cyst Nematode: A Model.

The pale cyst nematode, Globodera pallida, is a pest that poses a significant threat to potato crops worldwide. The most effective chemical nematicides are toxic to nontarget organisms and are now banned. Alternative control methods are therefore required. Crop rotation and biological control methods have limitations for effectively managing nematodes. The use of genetically resistant cultivars is a promising alternative, but nematode populations evolve, and virulent mutants can break resistance after just a few years. Masculinizing resistances, preventing avirulent nematodes from producing females, might be more durable than blocking resistances, preventing infection. Our demo-genetic model, tracking both nematode population densities and virulence allele frequencies, shows that virulence against masculinizing resistance may not be fixed in the pest population under realistic agricultural conditions. Avirulence may persist despite the uniform use of resistance. This is because avirulent male nematodes may transmit avirulent alleles to their progeny by mating with virulent females. Additionally, because avirulent nematodes do not produce females themselves, they weaken the reproductive rate of the nematode population, leading to a reduction in its density by at least 20%. This avirulence load can even lead to the collapse of the nematode population in theory. Overall, our model showed that combining masculinizing resistance, rotation, and biocontrol may achieve durable suppression of G. pallida in a reasonable time frame. Our work is supported by an online interactive interface allowing users (i.e., growers, plant health authorities, researchers) to test their own control combinations.

Post-fire recovery of nematode communities along a slope gradient in a pine forest.

We investigated the enduring consequences of a wildfire on nematode diversity and abundance in a pine forest, employing a slope gradient approach. Our primary objective was to determine the extent of post-fire alterations in the nematode community 3years after the incident, to understand if the ecosystem has returned to its pre-fire state or has transitioned to a distinctive ecological environment. Three distinct burned pine forest sites at varying elevations were sampled to capture short-scale soil property variations due to slope gradients, while unburned forest sites served as controls. A consistent pattern emerged where the lowest altitude sites exhibited the highest nematode abundances, although still lower than unburned sites. Fire-induced changes were profound, shifting from fungivore dominance in unburned sites to bacterivore and herbivore dominance in burned sites. Alterations in soil properties post-fire, particularly reduced organic matter and nitrogen content, were closely associated with nematode community shifts. Water availability played a crucial role with lower moisture levels at higher elevations impacting nematode populations. Structural differences in the nematode community primarily resulted from fire disturbance rather than altitude. This study emphasizes the persistent and transformative impact of wildfire on nematode communities, highlighting the intricate interplay between ecological disturbances, soil properties, and nematode trophic dynamics.

Effectiveness of Anaerobic Soil Disinfestation for Weed and Nematode Management in Organic Sweetpotato Production

Weeds and nematodes are particularly problematic in organic sweetpotato production due to a lack of effective pesticides. Anaerobic soil disinfestation (ASD) has the potential to fit into current pest management practices as an alternative to pesticide application. Greenhouse studies were conducted at the Clemson Coastal Research and Education Center (CREC) in Charleston, SC, to investigate the impact of carbon source amendment and a no carbon source treatment, and soil type on cumulative anaerobicity, weed control, nematode population, and sweetpotato vigor. Microcosms were filled with one of three different soil types (Charleston—loamy/native; Blackville—high coarse sand content; and Clemson—high clay content) and were mixed with cottonseed meal (CSM) or no carbon amendment. The pots were then sealed with plastic totally impenetrable film (Tif) for 6 weeks, followed by the transplanting of sweetpotato (cv Bayou Belle) slips. The results suggested that the CSM-treated microcosms spent more time under anaerobic conditions than those treated with the no carbon amendment. The microcosms that experienced a longer duration of anaerobicity had a lower percent weed cover (49%), fewer nematode egg masses, and a lower gall index when compared to microcosms which experienced a shorter duration of anaerobicity. Significantly higher instances of leaf necrosis were observed in the sweetpotato slips sown in the CSM-treated microcosms. The addition of CSM as a carbon source to facilitate ASD resulted in similar above-ground biomasses of the sweetpotato plants compared to the treatments containing no carbon amendment. However, a significantly lower below-ground biomass of the sweetpotato plants was observed in the CSM-treated microcosms.

Study on Impact of Soil Chemical Characteristics on Nematode Distribution Across Geographical Regions of Meghalaya

This study looks at the relationship between soil chemical characteristics and nematode communities in Meghalaya's agricultural landscapes. Nematodes, which are important bioindicators of soil health, were studied in connection to soil characteristics such as pH, Electrical Conductivity (EC), Organic Carbon (OC), and nutrient levels (N, P, K) in various parts of Meghalaya. The study found strong relationships between soil chemistry and the spread of various nematode taxa. Acidic soils with lower pH and higher organic carbon were shown to have higher populations of plant-parasitic nematodes such as Meloidogyne sp. and Xiphinema sp., both of which have been shown to reduce agricultural productivity. Soils with greater EC, on the other hand, have fewer of these damaging nematodes, implying that modifying soil salinity could be a viable technique for controlling nematode infestations. Furthermore, nutrient-rich soils, particularly those high in phosphorus and potassium, were associated with larger abundances of Tylenchorhynchus sp., emphasising the intricate relationship between soil fertility and nematode dynamics. The study highlights the critical impact of soil chemical characteristics in influencing nematode communities, as well as the importance of specific soil management strategies to improve crop health in Meghalaya. Farmers can use these findings to build targeted methods for controlling nematode populations, decreasing crop loss and encouraging sustainable agricultural practices in the region. This study offers useful recommendations for enhancing soil health and increasing agricultural productivity in some regions of Meghalaya's agroecosystems.

Quantifying the resistance of Australian wheat genotypes to Pratylenchus thornei based on a continuous metric from a factor analytic linear mixed model

Genetic resistance to the parasitic root-lesion nematode, Pratylenchus thornei, is one of the main management strategies cereal growers can use to minimise the impact of nematodes on winter cereal cropping. Screening of genotypes in the presence of P. thornei populations must provide reliable resistance measures that are realised under field conditions. Adoption of the latest statistical methodologies can help to better differentiate between resistant and susceptible genotypes. In this study, post-harvest P. thornei population densities were measured from a collection of 17 field experiments, with varying starting P. thornei population densities, conducted between 2011 and 2018 in locations across the northern grain growing region of eastern Australia. The experiments primarily consisted of wheat genotypes. The post-harvest P. thornei population densities were analysed across multiple environments in a linear mixed model framework, with a factor analytic structure used to model genotype by environment (G ×\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ imes$$\\end{document} E) interaction effects exclusively for wheat genotypes. In general, genetic correlations between environments were found to be high, indicating limited G ×\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ imes$$\\end{document} E interaction for resistance to P. thornei. Post-processing of results using the factor analytic selection tools (FAST) method provided a measure of the overall performance for each wheat genotype, as well as a stability measure reflecting the consistency of the resistance status across environments. The FAST method quantified genotype resistance on a continuous scale, better reflecting the nature of genetic resistance based on a quantitative variable such as nematode population density, and provided a statistically robust and informative means of aiding selection decisions for resistance to P. thornei.

Managing both overstory and understory vegetation mitigates the impact of drought on soil nematode communities in a Mediterranean pine forest

Forest management strategies can effectively mitigate the impacts of drought on tree species, but their effects on soil fauna remain largely unexplored. Among soil organisms, soil nematodes can serve as valuable bioindicators to assess the impact of forest management on soil biodiversity and soil functioning. Consequently, we investigated two related questions in a Mediterranean Pinus halepensis Mill. forest located in southeastern France. First, how do soil nematodes respond to forest management practices? Second, can forest management practices help modulate the effects of Mediterranean summer drought on these soil organisms? We conducted a field experiment in which we explored the influence of two forest management techniques—tree thinning (intense, moderate, or absent) and understory removal (shrubs present or absent)—on soil nematodes before and after the summer drought. We found that only total and bacterivorous nematode abundances were positively influenced by the forest management practices. The highest values were observed under conditions of intense thinning combined with shrub presence, with an average of 97,509 individuals per kg of dry soil. In contrast, the abundances of all nematodes, with the exception of predaceous nematodes, were lower after the summer drought with a reduction ranging from −55 % to −82 %. Total, bacterivorous, and fungivorous nematode abundances were less negatively affected by the summer drought under conditions of moderate thinning when shrubs were present versus absent. More generally, we discovered that bacterivorous and fungivorous nematodes were particularly sensitive to the forest management practices and the summer drought. It is thus apparent that habitat alterations induced by forest management can strongly affect nematode community structure and could therefore prompt shifts in ecosystem functioning. Finally, this study highlights that, in forests, understory vegetation can have significant positive impacts on soil nematode populations when severe dry periods occur.

Impact of Different Inoculum Levels of Cereal Cyst Nematode (Heterodera avenae) on the Physiological Traits of Wheat (Triticum aestivum)

This study aimed to examine the effects of various inoculum levels of H. avenae on wheat physiology. The experiments were conducted in the screenhouse at the Department of Nematology, CCSHAU, Hisar, with inoculum levels set at 5, 10, and 15 eggs and juveniles per gram of soil. Observations on physiological parameters were made 30 days post-sowing. It was found that increasing inoculum levels led to significant decreases in total chlorophyll, carotenoid content, chlorophyll fluorescence, photosynthetic rate, transpiration rate, and stomatal conductance. The highest inoculum level showed the most pronounced reductions, with respective decreases of 39.71%, 30.55%, 7.90%, 39.75%, 51.58%, and 64.86%. Highest nematode inoculum level also resulted in the highest reduction in gaseous exchange parameters, biomass and leaf pigments concentrations and maximum increment in nematode population density.

INFLUENCE OF ABIOTIC FACTORS ON DYNAMICS OF WHEAT PHYTONEMATODE IN MUGHAN PART OF AZERBAIJAN

The article deals with the impact of abiotic factors on the dynamics of wheat phytonematode in the Mughan part of Azerbaijan. To study the population dynamics of phytonematodes of wheat and its rootstock soil under Azerbaijan conditions, soil and plant samples were collected by stationary method monthly from March to June during 2018-2023. In the wheat field, 45 species of nematodes were recorded during the vegetation period. In both roots and rootstock of wheat, the highest number of phytonematode individuals was observed at the beginning of the study (March), then their density began to decrease sharply and reached a minimum at the end of the growing season (June). In aboveground parts, the highest peak of phytonematode abundance occurs in mid-spring (April), followed by a decline in abundance at the following dates. The lowest abundance is recorded in summer before harvesting. The recorded phytonematodes were distributed in the following ecological groups: polytrophs - 8 species, typical saprobionts - 2, devisaprobionts - 15, potential parasites - 12, true parasites - 8 species. Ecological groups of phytonematodes respond differently to changes in the conditions of existence. At the same time, the effect of ecological factors depended on the habitat of phytonematodes. It is known that in the Mughan region of Azerbaijan, the influence of abiotic factors on the dynamics of wheat phytonematodes mainly includes elements such as soil structure, climatic conditions, sunlight and water supply. These abiotic factors determine the level and distribution of nematode populations and affect the yield of crops. As a result of the changing influence of various abiotic factors, the population levels of nematodes also change, which affects the effectiveness in the crop field. In this regard, the understanding and management of these factors is important for improving the quality and production of wheat products. Preventive and preventive measures, depending on the completeness and timeliness of this information, allow you to create optimal conditions and get a stable harvest from plants. The above-mentioned issues have been extensively investigated and reflected in the article.

Characterization of finger millet extracts and evaluation of their nematicidal efficacy and plant growth promotion potential.

Plant-parasitic nematodes pose a significant threat to finger millet crops, potentially causing yield reduction of up to 70%. Extracts derived from finger millet varieties contain potent bioactive compounds that can mitigate nematode damage and promote plant growth. This study aimed at isolating and characterizing bioactive compounds from the finger millet varieties Ikhulule, Okhale-1, and U-15; evaluating the impact of Ikhulule and U-15 extracts on the mortality of the root lesion nematode Pratylenchus vandenbergae; assessing the growth promotion effects of Ikhulule and U-15 extracts on the finger millet variety Okhale-1; and determining the efficacy of these extracts in managing plant-parasitic nematodes under greenhouse conditions. Extracts were obtained from both leaves and roots and tested invitro for nematode mortality and invivo for growth promotion and nematode control. The results showed that finger millet extracts exhibited strong nematicidal properties invitro, achieving a mortality rate of up to 98% against P. vandenbergae nematodes. Applying these extracts to finger millet shoots significantly reduced nematode populations in both soil and roots and decreased the reproductive factor to below one (1), indicating an effective nematode control. The study attributes the enhanced nematicidal effects of finger millet extracts to their bioactive compounds, particularly dodecanoic acid, phytol, 1,1,4a-trimethyl-6-decahydro naphthalene, 2,3-dihydro-benzofuran, 2-methoxy-4-vinylphenol and ethyl ester, and hexadecanoic acid. These findings suggest that finger millet-derived extracts offer a natural solution for nematode management and broader agronomic benefits, ultimately contributing to overall plant health and productivity.

Understanding the dynamics of Meloidogyne incognita infestation in pomegranate orchards of Himachal Pradesh, India (year 2018, 2019 and 2021) and its management strategies

This study investigates the prevalence and dynamics of pomegranate wilt disease induced by Meloidogyne incognita across the Kullu, Mandi and Solan districts of Himachal Pradesh (India), revealed notable spatial and temporal variations in nematode populations and galling severity across the regions. The highest average nematode infestation of 9.25 % was observed at Nauni with highest counts of average second-stage juvenile (J2) larvae (449 larvae per 100 cc of soil) followed by Hurla (Kullu) with 7.42 % infestation. Correlation analysis reveals a strong positive relationship between larval population and galling severity suggesting a potential link between nematode levels and plant damage. Common disease symptoms were leaf size reduction, yellowing and gradual decline of pomegranate plants, often observed in patches within orchards. Microscopic identification revealed distinctive pear-shaped body of mature females while J2 larvae displayed vermiform shapes and the associated species of M. incognita was confirmed through examination of the perineal pattern. Pathogenicity test reveals initiation of leaf yellowing symptom after 45 days of inoculation of larval suspension and root galling was observed after 60 days onward followed by plant decline under greenhouse conditions. Results from pot and field experiments demonstrated the efficacy of Fluopyram and Fluensulfone in reducing nematode populations and galling severity. Treatment with drenching of Fluopyram at the rate of 2 ml/L reduced 98.56 % larvae under field and 99.00 % larvae/100 cc soil under pot conditions. Statistical analysis (paired t-test and MANOVA) confirms significant differences in galling severity and larval population before and after drenching. The study also underscores the importance of weed management in disease mitigation as several weed species (Chenopodium album and Solanum nigrum) were identified as potential reservoirs for M. incognita in infested pomegranate plant basin. This investigation contributes to the advancement of management practices for pomegranate cultivation that addresses both nematode and weed infestations ultimately enhancing crop resilience and productivity.

Utilizing endophytic plant growth-promoting bacteria and the nematophagous fungus Purpureocillium lilacinum as biocontrol agents against the root-knot nematode (Meloidogyne incognita) on tomato plants

AbstractThe present investigation was designed to assess how administering biocontrol agents (BCAs) made from the nematophagous endophytic fungus MR20 (Purpureocillium lilacinum) or a mixture of endophytic plant growth-promoting bacteria MR12 (Pseudomonas fluorescens), and MR25 (Serratia marcescens), could enhance tomato growth and resistance to Meloidogyne incognita under in vivo conditions. The three strains’ cell-free culture filtrates showed a strong nematocidal impact (P < 0.05) on M. incognita infective second-stage juveniles (J2s). The highest mortality rates by the three BCAs were at concentrations of 80%, followed by 60%, 40%, and 20%. The in vitro hatching of free eggs was found to be considerably (P < 0.05) reduced as the concentrations of the endophytic bacteria MR12, and MR25 were increased in the order 1 × 105, 1 × 106, 1 × 107, 0.5 × 108, to 1 × 108 colony forming units (CFU)/mL, and the maximum nematicidal activity in killing M. incognita free eggs occurred at 1 × 108 CFU/mL. A statistically significant (P < 0.05) reduction in the percentage of M. incognita-free eggs retrieved was seen in vitro when various concentrations of the endophytic fungus MR20 were applied compared to the negative control (distilled water). The endophytic fungus MR20 had the highest nematicidal activity against M. incognita free eggs at a concentration of 3 × 106 CFU/mL. The application of P. lilacinum or a combination of P. fluorescens and S. marcescens to tomato plants in the presence of M. incognita under greenhouse conditions resulted in a significant increase (P < 0.05) in root and shoot fresh weight, number of leaves, weight of leaves, and stem diameter when compared to the positive control treatment that contained only M. incognita. Treatment with P. lilacinum was more effective (P < 0.05) than P. fluorescens and S. marcescens in reducing egg masses per root, J2s per 100 g of soil, egg masses per 100 g of soil, J2s + eggs of M. incognita per 100 g of soil, reproduction factor, and reduction percentage after 60 days under greenhouse conditions. Nevertheless, the reduction of M. incognita gall size categorization (> 4 mm, 2–4 mm, and < 2 mm) was more effectively achieved by treatment with P. fluorescens and S. marcescens than by treatment with P. lilacinum. Under in vivo conditions, the tested P. lilacinum or a mixture of P. fluorescens and S. marcescens effectively controlled nematode population densities below the economic threshold.

Pathogenicity of Root-knot Nematode, Meloidogyne incognita on Tuberose (Polianthes tuberosa L.)

A pot experiment was carried out in the net house of Department of Nematology, Assam Agricultural University, Jorhat, to study the pathogenicity of root-knot nematode, Meloidogyne incognita, on tuberose. The study found that as the inoculum level of M. incognita increased from 10 to 10,000 second-stage juveniles (J2) per pot (containing 1 kg of sterilized soil), all plant growth parameters of tuberose decreased progressively. At the highest inoculum level, the plants became severely stunted, chlorotic, and produced very few bulblets. It was noted that at the highest inoculum level, the root systems were significantly reduced, with larger and mostly coalescent galls. The treatments with no nematode (check and associated check) were free from galls and eggmasses. An initial inoculum level of 100 J2 of M.incognita per kg of soil caused significant reduction in all growth parameters and proved to be pathogenic to the tuberose plants. The number of galls and eggmasses increased gradually in the plants with an initial inoculum level of 10 to 1000 J2 of M.incognita per kg of soil, but it declined at highest inoculum level of 10,000 J2 per kg of soil. The experiment also recorded the variation in nematode population in the soil as well as their reproductive rates. These findings can be used to develop effective, targeted methods for minimizing the damage caused by root-knot nematode in tuberose crops.

Bacillus, Pseudomonas and Serratia control Meloidogyne incognita (Rhabditida: Meloidogynidae) and promote the growth of tomato plants

Plant-parasitic nematodes cause significant losses in agriculture worldwide. Among these parasites, the root-knot nematode (Meloidogyne spp.) stands out. Consequently, control methods are being developed to combat this pest. Among these methods is biological control, the main agents of which are bacteria. This study aimed to evaluate the impact of 102 bacterial isolates on the mortality of Meloidogyne incognita J2 juveniles, hypothesizing that certain isolates could effectively control the nematode and promote tomato plant growth. Five experiments were conducted to test this hypothesis. First, the effect of the 102 bacterial isolates on J2 mortality was assessed under laboratory conditions. Second, five isolates (Bacillus cereus IBCBb130, Bacillus cereus IBCBb116, Pseudomonas aeruginosa IBCBb122, Bacillus proteolyticus IBCBb136, and Serratia sp. IBCBb118), which showed >68% J2 mortality, were evaluated over 72 h. Third, these isolates were tested at seven different concentrations. Fourth, their efficacy in controlling M. incognita on tomato plants was assessed in a greenhouse setting. Fifth, their potential to promote tomato plant growth without nematode inoculation was evaluated. The results revealed that the 102 bacterial isolates caused mortality ranging from 2 to 79.57% for M. incognita J2. At a 10% dilution, five isolates (B. cereus IBCBb130, P. aeruginosa IBCBb122, B. cereus IBCBb116, B. proteolyticus IBCBb136, and Serratia sp. IBCBb118) maintained mortality rates above 68%. Among these strains, B. cereus IBCBb130 and P. aeruginosa IBCBb122 were particularly effective, with B. cereus IBCBb130 showing high mortality rates under laboratory conditions and P. aeruginosa IBCBb122 significantly reducing nematode populations in greenhouse pots. Additionally, Serratia sp. IBCBb118 demonstrated notable potential for promoting tomato plant growth. In conclusion, specific bacterial isolates exhibit strong potential for the biocontrol of M. incognita and enhancement of tomato plant growth, suggesting a viable alternative to chemical nematicides. These findings provide insight into the development of sustainable agricultural practices through targeted manipulation of the soil microbiota. Future research should explore the underlying mechanisms of these interactions and their long-term effects on crop yield and soil health.

First report of Helicotylenchus dihystera parasitizing Lady Tankerville orchids (Phaius tankervilleae) in Vietnam.

Lady Tankerville, a rare orchid species (Phaius tankervilleae (Banks ex L'Hér.) Blume) in Vietnam, not only enhances the aesthetic value of the surroundings with its enchanting blooms but also holds high economic value (Aver'janov & Averyanova, 2003). Investigating the necrosis symptom on the root system and declined Lady Tankerville in the market in Hai Duong province in Vietnam from 11/2020 to 12/2021, we discovered a substantial infestation (24/24 plants were infected) of a spiral nematode, Helicotylenchus sp. The nematode population was extracted from the rhizosphere soil, roots, and stems of a single orchid using the modified Baermann tray technique (Whitehead & Hemming, 1965), for thorough characterization. The average nematode density was measured at 525±85 (350-670) nematodes/250 cm3 of soil, 202±56 (198-264) nematodes/15 g of roots, and 80±15 (72-95) nematodes/15 g of stem. Two hundred nematodes from the same population were inoculated into another healthy orchid for preservation and further infection tests. This species was morphologically identified as Helicotylenchus dihystera according to the key of Fotedar and Kaul (1985) and the description of Sher (1966). Morphometric measurements of the females (n = 12) are as follows: body length = 632-725 (681 ± 32) µm; a = 24-34 (28 ± 3); b = 5.1-7.2 (6.0 ± 0.6); b' = 4.3-6.4 (5.3 ± 0.6); c = 33-46 (39 ± 5); c' = 1.1-1.4 (1.2 ± 0.1); V = 62-78 (65 ± 4)%; O = 30 -49 (39 ± 6); stylet length = 21-26 (24 ± 2) µm; DGO = 9.2-12.4 (10.8 ± 1.1) µm. To validate morphological observations, molecular analyses of the ITS (Vrain et al., 1992) and the D2-D3 of 28S rRNA (Subbotin et al., 2006) were conducted. The ITS and D2-D3 sequences from this study (accession number: PP060444 and PP033748) exhibited the highest similarity of 99.8% and 100% to the sequence of H. dihystera in GenBank (KM506885 and MW023215), respectively. The infection test took place in a greenhouse at 28 ± 2℃. Three-month-old Phaius tankervilleae (n=8) were individually grown in 15 x 15 cm deep pots filled with sterilized sand and inoculated with 500 gravid females of H. dihystera (Rashid & Azad, 2013). Two noninoculated plants served as controls. After 60 days of inoculation, symptoms such as sunspots and root necrosis, observed in the market, appeared in the tested plants (Fig. S1). The presence and diagnosis of H. dihystera infestation in soil, roots, and stems across growth stages of orchids indicates the nematode to be an obligate parasite. The nematodes penetrate the roots, causing characteristic necrotic lesions initially yellow, then turn reddish-brown to black, along with brown root flecks in discolored tissues. Heavy infestations post-flowering led to extensive necrosis, distortion, and decay of the roots. The average reproduction factor (final population/initial population) of H. dihystera in this study was 22.2. Control plants remained symptom-free. Notably, 100% of tested plants were infected, highlighting the severe impact of H. dihystera. The nematodes were successfully reisolated and identified as H. dihystera through molecular analyses (accession number: PP060615 (ITS) and PP033748 (D2-D3)), reaffirming its identity. In addition to 32 host plants in Vietnam (Nguyen et al., 2023), our study reveals a strain of H. dihystera parasitizing Lady Tankerville orchids with a relatively high reproduction factor and infection rate. This marks the first reported instance of H. dihystera parasitizing Lady Tankerville orchids in Vietnam, emphasizing the need for proactive measures to protect this plant.

Lecanicillium psalliotae (Hypocreales: Cordycipitaceae) Exerts Ovicidal and Larvicidal Effects against the Sheep Blood-Feeding Nematode Haemonchus contortus through Its Liquid Culture Filtrates.

Nematophagous fungi (NF) form part of the soil microbiota and are natural enemies of nematodes, helping to regulate nematode populations. A verticillate NF isolated from soil from Tepalcingo, Mexico, was morphologically and molecularly characterised. This fungus was cultured in two different liquid media-Czapek-Dox broth (CzDoxB) and sweet potato dextrose broth (SPDB)-for 21 days. The ovicidal (OA) and larvicidal (LA) activities of fungal liquid culture filtrates (LCFs) were assessed in 96-well microtitre plates at different concentrations against Haemonchus contortus after 48 h. The morphological and molecular identification revealed the presence of Lecanicillium psalliotae. Additionally, the groups of compounds associated with nematocidal activity were determined from a qualitative chemical profile (QCP) using different reagents. The highest OA of the LCFs was obtained at 25 mg/mL from SPDB and CzDoxB and amounted to 97.2 and 99.06%, respectively. Meanwhile, the highest LA recorded with these LCFs at 100 mg/mL was 54.27% and 96.8%, respectively. The QCP revealed the presence of alkaloids and tannins in both LCFs that have previously been associated with nematocidal activity. Lecanicillium psalliotae exerted an important effect on H. contortus and could be of significance in future studies focused on the control and prevention of haemonchosis in small ruminants.

Effectiveness of four Turkish entomopathogenic nematode isolates against Bactrocera oleae (Diptera: Tephritidae) pupae at different temperatures

Türkiye, is the country of origin of the olive tree and is among the world’s leading olive producers. Most of the olive production in Türkiye is concentrated in Izmir, Aydın, Çanakkale, Balıkesir, Muğla and Bursa Provinces. Bactrocera oleae (Diptera: Tephritidae), being one of the main pests of olive trees, is an important problem in olive cultivation in Türkiye. The efficacy of four Turkish populations of entomopathogenic nematodes against B. oleae pupae was determined under laboratory conditions. They were Steinernema feltiae/12, S. carpocapsae/1133, Heterorhabditis bacteriophora/70, H. bacteriophora/91, which were collected in different regions of Türkiye during our earlier studies. They were tested against the pest by using a single dose at 5 different temperatures (10, 15, 20, 25 and 30 °C). The highest infection rate was observed forH. bacteriophora/91 isolate at 25 °C, and the lowest infection rate was observed for S. feltiae/12 isolate at 10 °C.

Morphological and molecular characterization of the European dagger nematode Xiphinema diversicaudatum on peach (Prunus persica) in Canada

Plant-parasitic nematodes (PPNs) pose a significant threat to global agriculture, leading to substantial yield losses. Managing nematode populations remains a challenging option due to financial, technical and environmental constraints. In Ontario, Canada, the presence of Xiphinema nematodes, a virus vector species, is of particular concern. This study reports the discovery of X. diversicaudatum in a peach field in Southern Ontario, Canada. The description includes morphological and molecular characterization using the 18S and 28S rDNA sequences. Morphological and molecular characterization of Ontario’s population matched those from Europe. While X. diversicaudatum was presumed eradicated from Canada, the present finding showed that the nematode could have spread beyond greenhouses. The study highlights the importance of intensive soil sampling for early nematode detection, even as strict reporting requirements may deter such efforts. We report for the first time the presence of X. diversicaudatum on peaches in Canada and in North America.