Nematode Populations Research Articles

Correlation Between Initial Nematode Population Density and Crop Losses Caused by Heterodera avenae in Wheat

An experiment was conducted to find out the effect of different inoculums levels(0, 2, 4, 8 and 16 cyst/plant)H. avenae on wheat. Among different inoculums level, highest females/5 g root (32.75), cysts per 200 cc soil (43.07) and juveniles per 200 cc soil (358.75) were recorded in 16 cyst/plant whereas lowest were recorded in 2 cyst/plant. Maximum shoot length (79.85 cm), shoot weight (28.84 g), root length (32.10 cm), root weight (7.71 g), fodder yield (23.72) and grain yield (15.81) were recorded in uninoculated plants (0 cyst/plant) whereas minimum was at 16 cyst/ plant. Significant reduction in plant growth characters were observed at and above 4 cyst/plant. Hence, experimental result revealed threshold level of 4 cyst per plant on wheat.

First report of anthelmintic resistance among sheep in six farms from three governorates in Jordan

This study aimed to identify the presence of gastrointestinal nematode populations resistant to albendazole, levamisole, and ivermectin in six farms located in three regions of Jordan (Irbid, Mafraq, and Ma'an). Infected sheep (40 per farm) with at least 100 eggs per gram were randomly divided into four groups (10 animals per group). Three groups were treated with ivermectin, albendazole, or levamisole while the fourth group was used as a negative control group. The standard faecal egg count reduction test (FECRT) was used to assess the drugs' efficacy. Resistance to ivermectin and albendazole was detected in all studied farms while resistance to levamisole was detected in four of the sampled farms. FECRT ranged from 55.6 % (90 % Confidence Intervals (CI): 29.6 % - 79.6 %) to 80.3 % (CI: 48.3 % - 92.1 %) for ivermectin, 77.4 % (CI: 53.2–86.7 %) to 95 % (CI: 85.8–97.6 %) for albendazole, and 86 % (CI: 46.1–95.6 %) to 99.4 % (CI: 97.6–99.7 %) for levamisole. Post-treatment copro-cultures, faecal floatation and/or Baermann technique indicated the presence of larvae of Haemonchus spp. in all of the sampled farms, followed by Nematodirus spp. in four farms, Trichostrongylus spp. in three farms, then Marshallagia spp. in one farm. This is the first study of its kind in Jordan that shows widespread anthelmintic resistance for gastrointestinal nematodes in geographically distant sheep farms in Jordan. Such widespread resistance to anthelmintics imposes a risk of failure to the present control programs and urges for changing the methodology of selecting effective anthelmintic treatments in local farms.

Fungi Preference of Fungivorous Nematode Aphelenchus avenae (Aphelenchida: Aphelenchidae) and Its Impact on Strawberry (Fragaria ananassa Duch.) Root

In continuously cropped strawberry soil, a large population of the fungivorous nematode, Aphelenchus avenae, was observed to increase significantly over time. This nematode, which feeds on pathogenic fungi affecting strawberries, has significant potential as a biocontrol agent. The purpose of this article is to discuss the nematode’s preference for fungi associated with strawberries and its impact on the growth of strawberry roots. With the exception of Trichoderma harzianum, most of the pathogenic fungi commonly found in strawberry soil, such as Fusarium oxysporum, Rhizoctonia solani, Verticillium, Phytophthora infestans, and Botrytis cinerea Pers. attracted A. avenae and supported their propagation. All treatments with A. avenae and the non-nematode control showed a consistent trend throughout strawberry development, indicating that a moderate amount of A. avenae does not adversely affect strawberry roots. Moderate and low levels of A. avenae significantly increased the activity of antioxidant enzymes, superoxide dismutase (SOD), and peroxidase (POD) in strawberry roots in all treatments during the entire growth stages. Also, the malondialdehyde (MDA) content of strawberry roots in all nematode treatments was lower than that in the no-nematode control. Despite an overabundance of A. avenae, which negatively affected the redox system balance of strawberry roots, A. avenae can protect the roots from pathogenic fungi by preventing infection and damage. These results lay the foundation for the potential use of A. avenae as a biological agent to control these pathogenic fungi in strawberry soil, in combination with the biological fungi (T. harzianum).

Prevalence and abundance of plant-parasitic nematodes in New Zealand maize fields: effects of territory, soil orders, crop stage, and sampling time

ABSTRACT Plant-parasitic nematodes (PPNs) are significant agricultural pests that can reduce maize yields. This study examines the prevalence, abundance, and diversity of PPNs in New Zealand maize fields, focusing on the effects of territory, soil orders, crop stages, and sampling times. Seven PPN genera were identified: Pratylenchus spp. (root-lesion), Helicotylenchus spp. (spiral), Meloidogyne spp. (root-knot), Heterodera spp. (cyst), Paratylenchus spp. (pin), Criconemella spp. (ring), and Tylenchus spp. PPNs were present in 98% of the samples, with Pratylenchus spp. being the most prevalent (91%), followed by Helicotylenchus spp. (38%). Compared to Waikato and Manawatu-Whanganui, Canterbury had the highest nematode populations, particularly of Pratylenchus spp. and Helicotylenchus spp. Brown and pallic soils supported higher PPN abundances. Sampling during the maize harvesting stage and late autumn resulted in the highest nematode populations and diversity indices. Pratylenchus spp. populations often exceeded the economic threshold of 500 Pratylenchus kg−1 of soil, suggesting a significant threat to maize yield in New Zealand. The findings highlight the need for further research to assess the impact of Pratylenchus spp. on maize yield and to develop effective management practices for maize cultivation in the country.

Sustainable Management of Root-knot Nematodes in Tomatoes: Effects of Inoculum Levels under Polyhouse Conditions in Northeast India

The study aims to evaluate the impact of different inoculum levels of root-knot nematodes (Meloidogyne spp.) on tomato plants under polyhouse conditions in Northeast India. The research provides early predictions of nematode infestation severity and guides farmers on sustainable management practices, including biological control, to keep nematode populations below the economic threshold. Soil samples from key tomato-growing areas in Nongpoh, East Khasi Hills, and West Jaintia Hills districts of Meghalaya were collected, and inoculum levels ranging from 500 to 8000 J2 were tested using completely randomized design. The study found a significant increase in root gall index, egg mass production, and nematode population with higher inoculum levels. Even low inoculum levels (500 J2) caused notable damage to the plants. These findings underscore the importance of managing nematode populations early to reduce crop losses and highlight the need for efficient, low-inoculum control strategies. This study contributes to the sustainable management of nematodes in agricultural practices.

Management of Root-Knot Nematode, Meloidogyne incognita Infecting Tuberose by Using Bioformulations under Field Condition

Aims: To evaluate the effectiveness of different bioformulations for management of root-knot nematode, Meloidogyne incognita infecting tuberose under field condition. Study Design: Randomized Block Design. Place and Duration of Study: Biswanath College of Agriculture, AAU, Biswanath Chariali, Assam during summer season 2024. Methodology: Bulbs of tuberose cultivar Prajwal were planted in root-knot nematode infested sick plot. In this experiment seven treatments were considered and the treatments were replicated thrice. Bioformulations viz., Neem cake, Neem leaf power, Biover, Biozium, Biomonas and AAU-Bioguard were applied treatment wise and mixed with soil before planting of bulbs. Observations on plant height and floral characteristics viz. spike length, rachis length, spike weight, number of floret per spike, floret length and nematode multiplication parameters like number of galls, egg masses per root system and final nematode population in soil were recorded. Results: Upon observation results showed that all the treatments were significantly effective in increasing the plant height, floral characteristic and reducing the number of galls, eggmasses and final nematode population in soil as compared to that of untreated control. Highest plant height(46.50cm), spike length (66.33cm), spike weight (37.33g), rachis length(32cm), number of florets per spike(25.26) and floret length(4.66cm) was recorded in the treatment with Biover@5kg enriched with FYM 5t/ha, which was followed by the treatment with Biozium @5kg enriched with FYM 5t/ha and neem cake @ 1t/ha. Maximum reduction of number of galls (35.18%), eggmasses (31.79%) and final nematode population in soil (39.65%) was recorded in the treatment with Biover@5kg enriched with FYM 5t/ha. Conclusion: From this experiment it can be concluded that all the bioformulations were found to be effective for increasing plant height, floral characteristic and reducing the nematode multiplication and these can be incorporated in root-knot nematode management programme. Among the bioformulations Biover was found to be most effective.

Changes in the population and diversity of plant parasitic nematodes and their effects on sugarcane growth at Wonji‐Shoa Sugar Estate, Ethiopia

AbstractIn Wonji‐Shoa Sugar Estate (WSSE), sugarcane (Saccharum spp. hybrid) yields have declined by about 48% over the last 70 years. One of the causes for the decline is assumed to be the long‐term monoculture production system that results in the buildup of plant parasitic nematodes (PPNs). Therefore, the population and diversity of PPNs were investigated by conducting soil sampling using a biosequential method (simultaneous sampling of the soils of adjacent cultivated land [CL] and uncultivated land [UL]) and a chronosequential method (taking soil samples at different times from the same site). The samples were subjected to analysis using standard procedures to determine the change in the population, and identify the genera of PPNs. Additionally, a pot experiment that involved fumigation was conducted on top soils sampled from the CL and UL of the plantation. The results revealed that about 10 genera of PPNs (Meloidogyne, Helicotylenchus, Hoplolaimus, Rotylenchulus, Hemicycliophora, Discriconemella, Xhiphinema, Pratylenchus, Tylenchorhynchus, and Scutellonema) were detected, of which the first four were newly identified. The population density and the number of genera of PPNs found in the CL were 36‐fold and 4.5‐fold higher than those found in the UL, respectively. Furthermore, fumigation reduced the population of the PPNs by 61% and increased production of cane biomass by 63%. It is concluded that the soils of the WSSE are infested by PPNs, which consequently have detrimental effects on sugarcane growth. While amending soil fertility is crucial, reversing the decline in sugarcane yields also necessitates implementing an integrated soil management system that includes PPNs.

Floral Infestation of Tuberose with Aphelenchoides and Its Management

In the field experiment conducted on cv. Calcutta Double, the symptoms of floral malady and efficacy of treatment modules on foliar nematode population, percent infestation and resulting yields of the crop has been observed. The symptoms appear on the leaves and progress until flowering. Typical symptoms observed were browning of leaves and flowers. In serious condition, the plant becomes stunted along with prickles on the stalks and flowers. The flowers become brittle. The results of the present study showed that the percent infestation was directly proportional to the nematode population. The percent infestation and the population were higher in untreated plot (M7) as compared to all treated plots. The treatment module (M4) involving overnight drenching of bulb in water followed by dipping in monocrotophos 36SL @750ppm for 4 hrs + Spraying of monocrotophos 36SL @360g a.i./ha alternated with cartap hydrochloride 50SP @375g a.i./ha at 15 days interval after onset of foliar nematode infestation in the 1st year and succeeding year crop was the most economical (ICBR 1: 8) and effective means of managing Aphelenchoides besseyi population. It also yielded higher number of marketable flower stalks viz. 4, 43,908.19 per hectare.

Eco-friendly biocontrol of pine wilt disease: Enhancing tree defense with Bacillus subtilis JCK-1398 for sustainable forest management

Pine wilt disease (PWD), caused by pinewood nematodes (Bursaphelenchus xylophilus), poses a significant threat to forestry worldwide. This study introduces a novel biocontrol strategy using Bacillus subtilis JCK-1398, which was selected and identified for its resistance-induction potential after extensive screening of microbial strains from pine tissues. The bacterium was found to biostimulate resistance in Pinus densiflora. Comprehensive analyses, including transcriptomics, qPCR assays, and high-performance liquid chromatography (HPLC), revealed that B. subtilis JCK-1398 significantly upregulates defense-related genes and stimulates pinoresinol production, a compound linked to resistance against nematodes. Treatment with B. subtilis JCK-1398 suppressed nematode migration and reduced nematode populations within pine tissues, effects attributed to the enhanced tree defense response. Field trials corroborated these findings, demonstrating a 72 % decrease in PWD incidence with aerial application of JCK-1398, confirming its potential for large-scale forest application. This biocontrol strategy, leveraging the stimulation of plant defense by B. subtilis JCK-1398, presents a promising and scalable, eco-friendly solution for managing PWD. Overall, this study provides new insights into the interactions between the bioagent, the host tree, and the pest nematode, offering an effective and sustainable approach to mitigate pine wilt disease.

Effectual role of plant growth-promoting fungi and fosthiazate in controlling tomato root-knot nematode infection: In vivo and in vitro studies

Plant growth-promoting fungi (PGPF) are known to induce systemic resistance in plant diseases caused by microbial pathogens. However, the induced resistance by PGPF has not yet been elucidated in plant diseases caused by root-knot nematodes (RKNs, Meloidogyne spp.). Meloidogyne incognita can severely damage tomato plants, causing considerable losses in world yields. This study aimed to isolate and evaluate the potential of PGPF through enhancing systemic resistance, possibly through activating defense-related pathways in tomato plants, comparing to the commercial chemical nematicide, Melithorin® (fosthiazate 90 %). The most potent PGPF (K7, K13, K14) were identified morphologically and molecularly as Alternaria photistica, Penicillium buchwaldii, and Aspergillus niger, respectively. We tested the efficacy of these fungi against RKN (M. incognita) both in vitro and in vivo. The results demonstrated that the commercial nematicide fosthiazate (90 %) was the most effective treatment for controlling RKN J2 larvae, achieving a mortality rate of 94 % after 96 h. This was followed by the PGPF treatments, with A. niger at 92.6 %, P. buchwaldii at 87.7 %, Verticillium lecanii at 73.3 %, and A. photistica at 47.4 %. Additionally, applying A. photistica, A. niger, P. buchwaldii, and V. lecanii significantly enhanced the levels of photosynthetic pigments, total carbohydrates, and proteins in both healthy and RKN-infected plants. Notably, Melithorin® (fosthiazate 90 %), A. niger, and V. lecanii led to substantial increases in root carbohydrate content, with increases of 97 %, 63 %, and 58 %, respectively. Furthermore, Melithorin®, A. photistica, and A. niger significantly boosted shoot protein content by 68 %, 65 %, and 49 %, respectively, compared to the infected control group. These findings indicate that both nematicide and fungal treatments effectively reduce nematode populations and improve overall plant health and nutrient composition. At the same time, the results appeared that infected plants treated with PGPF or Melithorin® showed variation in number and molecular weight of protein bands. SDS-PAGE results indicated that, the highest number of bands (twelve) was recorded in the infected plants treated with Melithorin® followed by P. buchwaldii (11 bands), A. photistica (10 bands), V. lecanii (8 bands), and A. niger (7 bands), respectively. Also, the application of Melithorin®, A. niger, and V. lecanii resulted in a significant increase in the number and weight of fruits, respectively, compared to healthy control plants. Our results suggested that A. photistica, A. niger, P. buchwaldii, and V. lecanii could be used as effective and safe nematicides against RKNs.

Use of the Micro-Agar Larval Development Test to Differentiate Resistant and Susceptible Cooperia spp. Isolates in Cattle Within the Context of Parasite Population Replacement.

Gastrointestinal nematode infections are a global concern in grazing cattle production systems, even more so due to the widespread problem of anthelmintic resistance. In response, early anthelmintic resistance detection methods, such as the micro-agar larval development test (MALDT), and parasite management strategies, such as the replacement of resistant parasite populations with susceptible ones, have been developed. This study aimed to characterize ivermectin-susceptible and -resistant isolates of Cooperia spp. using MALDT in the context of a parasite population replacement strategy. Three Cooperia spp. field isolates were evaluated: a susceptible one (Coop-S), a resistant one (Coop-R), and a post-replacement one (Coop-PR). The MALDT was performed in 96-well plates with 12 known concentrations of eprinomectin (EPR) on an agar base. Each test was performed in quadruplicate. Data analysis included nonlinear regression to determine EC50, EC90, and EC99 values, resistance ratios (RRs), and R2. The results showed clear differentiation between the isolates, with RR values of 5.78 and 1.28 for Coop-R and Coop-PR, respectively, compared to Coop-S. The MALDT proved to be a reliable tool for differentiating ivermectin-susceptible from ivermectin-resistant isolates of Cooperia spp., and future evaluations of this test in mixed nematode populations are recommended for routine diagnosis of anthelmintic resistance.

Tomato Root Exudates Infected by Meloidogyne incognita Impact the Colonization of Nematicidal Proteus vulgaris.

Root exudates play a pivotal role in shaping the microbial community in the rhizosphere and can impact the efficacy of bacteria in controlling nematode populations. This study identified Proteus vulgaris BX-1 as significantly effective in controlling Meloidogyne incognita. The infection of tomato plants with this nematode induced noticeable alterations in the composition of tomato root exudates and led to an increased colonization rate of strain BX-1. Further investigation into how strain BX-1 responded to changes in tomato root exudates revealed that specific metabolites, such as caffeic acid, coumarin, salicylic acid, sebacic acid, and butyric acid, strongly attracted strain BX-1. This attraction potentially contributed to its enhanced colonization and improved efficiency in controlling nematodes. Understanding the correlation between specific metabolites in root exudates and the response of antagonistic bacteria provides valuable insights for enhancing their effectiveness as biological control agents against plant-parasitic nematodes.

Deciphering the Biocontrol Potential of Trichoderma asperellum (Tv1) Against Fusarium-Nematode Wilt Complex in Tomato.

The study assessed Trichoderma spp. as a biocontrol agent for managing wilt-nematode complex in tomato crops, aiming to mitigate yield losses. Fusarium sp. and Meloidogyne sp. were isolated from infected plant samples and confirmed molecularly and morphologically as Fusarium oxysporum f.sp. lycopersici and Meloidogyne incognita. Four Trichoderma spp. procured from the Department of Plant Pathology, Tamil Nadu Agricultural University, India were identified molecularly as Trichoderma asperellum (Tv1), Trichoderma asperelloides (Tasd1), Trichoderma harzianum (Th1), and Trichoderma koningiopsis (Tk1) utilizing ITS and TEF1 primer pairs. Among them, Tv1 effectively inhibited the mycelial growth of pathogen isolates. Furthermore, crude metabolite of Tv1 exhibited similar effects. The mortality rate of M. incognita J2s ranged from 90.48% to 100% after 24-72 h of incubation and inhibition percentage of egg hatching reached 90.20%. The shoot length, root length, fresh weight, and dry weight of the tomato plants treated with Tv1 conidia were increased. In a pot experiment, Tv1 treatment reduced disease incidence by 64.57%, comparable to carbendazim treatment (82.32%). Tv1-treated plants had fewer root galls, egg masses, and J2s per 100 g of roots than the inoculated-untreated control plants. The root-knot index (RKI) was significantly lower in plants treated with carbafuran (1.98 ± 0.047) and Tv1 (3.06 ± 0.086) than in control (4.47 ± 0.109). The bio-control efficiency of Tv1 against M. incognita was 21.04%, and the nematodes' reproductive factor (RF) declined to 0.53 in Tv1 treatment group. Based on the findings above, it was established that Tv1 effectively controlled nematode populations and wilt disease when applied in soil.

Response of host Indian Musa germplasm against artificially induced root lesion nematodes (Pratylenchus coffeae)

Under greenhouse condition, the host response of fifty-nine banana genotypes (Musa spp.) from the Eumusa section to the root-lesion nematode (Pratylenchus coffeae) was assessed. In a factorial completely randomized design (FCRD) with five replications, healthy banana suckers of the diploid and triploid accessions were planted in cement pots. Uninoculated controls were included in the experiment as comparison to study the sensitivity of the genotypes. Two varieties (Pisang Lilin and Nendran) with known reaction to lesion nematode were also included as reference clones because of their resistance and susceptibility to P. coffeae. Banana accessions maintained in the pots were inoculated with infective juveniles of root-lesion nematode, P. coffeae at 45 days after planting at the rate of 400 nematodes/pot. Ninety days after inoculation, the plants were harvested to observe the response of the different banana genotypes to P. coffeae. Data were recorded on plant growth (plant height, girth at the base, number of standing leaves, number of roots and weight of the root system), root damage assessment (percentage of infected roots and percentage necrosis) and nematode reproduction. When inoculated with nematodes, the reduction in plant growth attributes was relatively higher in genotypes that were susceptible. The reduction in growth characters viz., plants height, number of roots and root fresh weight were maximum in the diploid genotypes Manguthamng (26.80, 27.2, 33.0 %) and Manohar (25.70, 29.2, 35.2 %) and in the triploid genotypes Kaali, Rajthali, Digjowa, Saapkal, Cheenichampa, Dasaman, Borchampa, Jahaji, Manjahaji, Barjahaji and Sabri when inoculated with Pratylenchus coffeae. Even after nematode inoculation, root investigations showed that resistant and tolerant genotypes had greater numbers of roots as well as high fresh and dry weight of roots. Root and soil population of nematodes assessed at 90 days after inoculation indicated very high population buildup of Pratylenchus coffeae (>28) in diploids Manguthamng and Nendrapadathi and in triploids Jahaji, Manjahaji, Saapkal, Borchampa, Therahaw-1163 and 1164, Ankur-I and Bersain. The rate was the lowest (<9) in the diploid genotypes Kanai Bansi, Kechulepa, M.balbisiana, Athiakol, Bhimkol and Aittakola and in the triploids Karthobiumtham and Ankur-II. The results of the experiment showed that the diploids Musa balbisiana (BB), Aittakola (BB), Bhimkol (BB), Kechulepa (BB), Kanai Bansi (AA) and Athiakol (BB) and the triploid genotypes Kachkel (ABB), Karthobiumtham (ABB) and Ankur-II (ABB) were resistant to Pratylenchus coffeae.

Pleurotus ostreatus is a potential biological control agent of root-knot nematodes in eggplant (Solanum melongena)

IntroductionThe management of root-knot nematodes has predominantly been based on use of chemicals, which are detrimental to the environment and human health. Biological control provides alternative management. This study evaluated the potential of using Pleurotus ostreatus, an edible mushroom species to control Meloidogyne spp. in eggplants.MethodsIn vitro, the mortality of juveniles (J2) of Meloidogyne spp. were assessed i) P. ostreatus - water suspension with actively growing mycelia, and ii) different dilutions of P. ostreatus PDB broth culture filtrates. In the screen house nematicidal potential of P. ostreatus was tested on eggplants using artificially inoculated soils in a screen house. To attain this, juveniles (J2) of Meloidogyne spp. were inoculated at the base of plants in pots containing P. ostreatus colonized millet grains mixed in 3 kg of soil. The galling index (GI) (scale of 0 to 5), root growth and nematode populations in the different treatments were assessed.Results and discussionMortality of nematodes in the P. ostreatus - water suspension significantly increased with time, reaching over 88% at 48 h and 95% at 72 h. Mortality in undiluted filtrate was consistently significantly higher than the diluted filtrates and control without P. ostreatus. Mortality in the undiluted filtrate increased to 95% at 48 h. When 50 g of P. ostreatus-millet culture was mixed with 3 kg autoclaved pot soil, a GI of 0.95 was observed, dropping to 0.70 when the inoculum was doubled to 100 g. For the treatment without P. ostreatus, a high GI of 2.4 was scored. A significant difference in eggplant root growth and nematode population at (p = 0.02) was found across the treatments. The findings from this study for both in-vitro and pot assay suggest that P. ostreatus and its substrate are potential biological control agents for plant parasitic nematodes in eggplants.

Prevalence and Characterization of Plant-Parasitic Nematodes Existing in RD41 Rice Fields in Pathum Thani Province, Thailand, with Emphasis on Hirschmanniella mucronata and Meloidogyne graminicola

Plant parasitic nematodes (PPNs) are one of the most destructive pests affecting rice growth worldwide. In this study, populations of PPNs associated with RD41 rice fields in Pathum Thani Province, Thailand, were surveyed and the dominant PPNs found in the fields were identified using a combination of morphological and molecular traits. A total of 105 soil or root samples were taken from 21 paddy fields in 7 districts of Pathum Thani, and nematode extraction was processed in a laboratory. In all sampled rice fields, 6 nematode genera, namely Hirschmanniella sp., Meloidogyne sp., Pratylenchus sp., Tylenchorhynchus sp., Helicotylenchus sp., and Tylenchus sp., were extracted. Of these 6 nematode genera, Hirschmanniella sp. was the most prevalent in both soil and root samples (66.7 - 100 % occurrence observed), followed by Meloidogyne sp., which was found in only 4 districts of the province (0.2 to 8.7 % occurrence observed). The species of these predominant PPNs were morphologically and molecularly characterized. The identification results remained consistent across morphological features and molecular techniques, confirming the presence of Hirschmanniella mucronata and Meloidogyne graminicola in the studied rice fields. The results of this study provide useful baseline data of the occurrence of PPNs in Thailand's rice fields. The incidence of some PPNs found in this study is likely to become a significant factor limiting rice production yields if they are not better managed. HIGHLIGHTS Plant-parasitic nematode (PPN) populations in RD41 rice fields located in Pathum Thani province, Thailand were examined Six PPN genera were extracted from soil and root samples The predominant PPNs were characterized using morphological and molecular traits The main PPNs were identified as mucronata and M. graminicola This study provides useful baseline data of PPNs found in Thailand's rice fields GRAPHICAL ABSTRACT

Cavalcade Legume (Centrosema pascuorum) Used as Soil Amendment in RD41 Rice Fields: Short-term Effects on the Soil Nematode Community, Soil Properties, and Yield Components

Numerous phytoparasitic nematodes have been identified in Thailand’s paddy fields, which routinely cause substantial reductions in rice crop yields. However, effective strategies for their management have yet to be documented. In this study, cavalcade legume was used as a soil amendment in RD41 rice fields to examine its effects on the soil nematode community, soil properties, and yield components compared to untreated control plots. The results demonstrated that the population densities of plant-parasitic nematodes (PPNs) in the order Tylenchida, primarily Hirschmanniella sp., significantly decreased in cavalcade-treated plots across all soil sampling periods. Moreover, there was an increase in the populations of beneficial nematodes within the orders Dorylaimida and Araeolaimida. In contrast, greater PPN populations were observed in the control plots compared to the initial nematode population. In addition to reducing PPN populations, this legume showed other benefits, specifically increased soil properties (available P) and rice plant growth (plant height and number of tillers). While there was no statistically significant difference in soil organic matter (SOM) content, the application of this legume tended to increase SOM content, in contrast to a decrease in SOM content observed in the control plots. Overall, this study provides valuable insights into the substantial advantages of using cavalcade legumes in RD41 rice fields.

Timing of Plant Extracts Application in the Management of Meloidogyne incognita on Tomato Plants

Meloidogyne incognita, a widespread and damaging plant parasite, reduces crop yields. Chemical treatments are common but pose health and environmental risks, leading to a search for safer alternatives. Plant extracts with secondary metabolites, like those from Maerua angolensis and Tabernaemontana elegans, show promise for nematode control, though their efficacies vary. This study aimed to investigate how the timing of applying T. elegans and M. angolensis extracts influenced the population densities of M. incognita and the growth of tomato (Solanum lycopersicon L.) plants. The experiment was a factorial design with two plant extracts applied at 5 g per plant and three different timings of application relative to nematode inoculation. Additionally, the experiment included positive (chemical standard (Nemacur® 10 GR)) and negative (plants inoculated with nematodes only) controls, alongside naturally grown plants. The results indicate that applying plant extracts before the nematode inoculation or simultaneously with the inoculation reduced the total nematode populations as effectively as the Nemacur positive control. Plants treated with extracts showed improved growth variables compared with those treated with Nemacur® and the natural growing conditions. In conclusion, applying plant extracts before or simultaneously with nematode inoculation effectively suppressed the nematodes and enhanced the plant growth variables. These findings suggest that such plant extracts could be adopted as part of integrated nematode management strategies in agricultural settings.

Prevalence and Diversity of Plant Parasitic Nematodes in Irish Peatlands

The prevalence of plant parasitic nematodes (PPN) in the Irish peatlands was investigated in five different peatland habitats—raised bog, cutover scrub/woodlands, fens and peat grasslands, which were further sub-categorised into fourteen different sub-habitats. Within the raised bog habitat were healthy bog hummock (HBH), healthy bog lawn (HBL), degraded bog hummock (DBH) and degraded bog lawn (DBL) and the fen habitats were fen peat (FP) and rich fen peat (R-FP). Cutover scrub or woodland habitat included cutover scrub rewetted (C-RW), cutover scrub non-rewetted (C-NRW), woodlands rewetted (W-RW) and woodlands non-rewetted (W-NRW). Grassland included wasted peat (WP), rough grazing (RG-I) and improved fen peat grassland (IFPG-RW and IFPG-NRW). Soil samples from peatlands were all collected between July and December 2023 when the temperature ranged from 12 to 20 °C. One half of each sample was used for molecular nematode analysis and the other half for morphological identification of nematodes. For the morphological identification, a specific nematode extraction protocol was optimised for peatland soils, and the extracted nematodes were fixed onto slides to be studied under a high-power light microscope. Subsequently, the other part of the soil was processed to isolate total DNA, from which the 18S rRNA gene was sequenced for the identification of nematode taxa. The extracted DNA was also used for randomly amplified polymorphic DNA (RAPD) fingerprinting analysis to determine banding patterns that could classify different bog habitats based on PPN random primers. Compared to that in the climax habitats (HBH, HBL, DBH, DBL, FP, R-FP), PPN prevalence was recorded as being higher in grasslands (WP, RG-I, IFPG-RW and IFPG-NRW) and scrub/woodland ecosystems (C-RW, C-NRW, W-RW, W-NRW). The results indicate that nematode populations are different across the various bog habitats. Emerging and current quarantine PPN belonging to the families Pratylenchidae, Meloidogynidae, Anguinidae and Heteroderidae were noted to be above the threshold limits mentioned under EPPO guidelines, in grassland and wooded peatland habitats. Future actions for PPN management may need to be considered, along with the likelihood that these PPN might impact future paludiculture and other crops and trees growing in nearby agricultural lands.

The Distribution of Reniform Nematode (Rotylenchulus reniformis) in Cotton Fields in Central Queensland and Population Dynamics in Response to Cropping Regime.

Reniform nematode (Rotylenchulus reniformis) causes significant yield loss in cotton worldwide. In 2012, its detection in the Dawson-Callide region of Central Queensland prompted extensive surveys of cotton fields. The nematode was confirmed in 68% of sampled fields, with populations ranging from 2 to 3870 R. reniformis/200 mL of soil. Soil monitoring revealed increasing populations associated with consecutive cotton crops. However, when corn or sorghum replaced cotton, soil nematode populations significantly decreased. A two-year replicated field trial demonstrated that growing a non-host crop (such as biofumigant sorghum 'Fumig8tor', grain sorghum, or corn) significantly reduced nematode populations in the top 15 cm of soil compared to cotton. Unfortunately, when cotton was replanted the following season, nematode populations rebounded regardless of the previous crop. Only the 'Fumig8tor'-cotton rotation resulted in significantly lower nematode populations than continuous cotton. Vertical soil sampling showed that rotating with a non-host crop significantly reduced nematode densities to a depth of 100 cm compared to cotton. However, when the field was replanted with cotton, nematode populations recovered, unaffected by cropping or soil depth. This study emphasises the importance of monitoring reniform nematodes in cotton soils for early detection and defining distribution patterns within a field, which may improve the effectiveness of management practices. These results suggest that one rotation out of cotton is not sufficient, as populations return to high levels when cotton is grown again. Therefore, two or more rotations out of cotton should be considered to manage this nematode.