Most Australian vegetable growers apply fumigants or nematicides as a precautionary nematode control measure when crops susceptible to root-knot nematode (RKN, Meloidogyne spp.) are grown in soils and environmental conditions suitable for the nematode. The only way growers can make rational decisions on whether these expensive and environmentally disruptive chemicals are required is to regularly monitor RKN populations and decide whether numbers prior to planting are high enough to cause economic damage. However, such monitoring programs are difficult to implement because nematode quantification methods vary in efficiency and the damage threshold for RKN on highly susceptible vegetable crops is often < 10 root-knot nematodes /200 mL soil. Consequently, five nematode quantification methods were tested to see whether they could reliably detect these very low population densities of RKN. Two novel methods produced consistent results: 1) extracting nematodes from 2 L soil samples using Whitehead trays, quantifying the RKN DNA in the nematode suspension using molecular methods, and generating a standard curve so that the molecular results provided an estimate of the total number of RKN individuals in the sample, and 2) a bioassay in which two tomato seedlings were planted in pots containing 2 L soil and the number of galls produced on roots were counted after 21-25 days. Both methods could be used to quantify low populations of RKN, but bioassays are more practical because expensive equipment and facilities are not required and they can be done at a local level by people lacking nematological or molecular skills.

BackgroundTomato yield is significantly reduced by root-knot nematodes (RKN; Meloidogyne spp.), particularly in tropical and subtropical regions. This study evaluated 20 bacterial isolates (B1-B20), belonging to the genera Bacillus, Lysobacter, Paenibacillus, and Streptomyces, from Sekem farms in Egypt for their potential to biocontrol RKN and stimulate plant growth in tomato 'Moneymaker.' The bacteria were compared to well-known microbial biocontrol agents (MBA), including Rhizobium etli G12 (B21), Pseudomonas trivialis 3Re2-7 (B22), Sporosarcina psychrophile Sd4-11 (B23), and B. subtilis Sb1-20 (B24), and a negative control, Escherichia coli JM109 (B25). The study involved seed-coated and -uncoated plants with bacterial isolates, planted in plastic pots, and inoculated with 1500 M. incognita J2 individuals per pot. Plants were grown in a saran-house during the 2022 and 2023 fall seasons, and their RKN-satisfying response (number of galls: NG and egg masses: NEM), vegetative growth, and metabolic activity were assessed 45 days after inoculation.ResultsIn seasons of 2022 and 2023, seed coating with bacterial isolates achieved a significant improvement in plant growth (coefficient of variation: CV ranging 26.8-120.2% in 2022 and 10.9-48.8% in 2023) and a reduction in RKN-satisfying response (CV for NG: 57.6 and 53.8%, respectively; and for NEM: 56.5 and 65.3%, respectively). Compared to uncoated-seed plants, the bacterial seed coating reduced NG by 0.66-74.09% in 2022 and 14.61-66.29% in 2023. Similarly, NEM decreased by 0.63-70.61% in 2022 and 41.91-77.46% in 2023. The coated-seed plants by Bacillus subtilis subsp. spizizenii (B5), Streptomyces subrutilus Wb2n-11 (B12), Streptomyces scabiei (B19), and Bacillus mojavensis (B20), along with the well-known MBAs B22 and B23, showed increased photosynthetic pigments, fresh weight of roots and shoots, stem size, and number of leaves. This growth has also led to higher dry weights in roots and shoots, and an increase in the root content of carbohydrates and proteins. Seed coating induced systemic RKN resistance by increasing polyphenols in the root. In contrast, uncoated-seed plants showed reduced foliar photosynthesis pigment and metabolic activity due to high RKN damage. Principal component analysis revealed significant correlations among the evaluated traits. Hierarchical clustering categorized bacteria isolates into five clusters based on their impact on estimated plant traits.ConclusionB5, B12, B19, B20, B22, and B23 demonstrated superior performance in both controlling RKN and stimulating vegetative growth in tomato 'Moneymaker' plants as known MBAs.

Several perennial and annual crops in the northern coast of Peru significantly reduce their productivity due to the damage caused by root-knot nematodes (RKN, Meloidogyne spp.). Routine nematode analyses carried out on these crops detected the presence of Pasteuria penetrans (Thorne) Sayre and Starr endospores attached to second stage juveniles (J2) of RKN. Soil sampling was carried out in different valleys to determine the prevalence and the number of attached endospores of P. penentrans. We also compared whether the differences between population fluctuations of Meloidogyne incognita (Kofoid and White) Chitwood in soils infested and not by P. penetrans were linked to a potential suppressive effect. 17.8% of soil samples collected from grapevine, pepper and banana plants in the valleys of Medio Piura, Bajo Piura, Alto Piura, Chira, San Lorenzo and Olmos showed presence of P. penetrans. No endopores were found in samples from crops such as sugar cane and asparagus. An average of 30.5 endospores per nematode was estimated. The J2 populations found in grapevine cultivated soils not infested with P. penetrans were 1.7 to 2.3 times higher than in soils infested by P. penetrans. The percentages of J2 with endospores were correlated (rho = 0.35; P < 0.02) with the abundance of M. incognita populations. These results confirm the widespread occurrence of P. penetrans in the crops and valleys sampled and its biological potential as a natural suppressor of Meloidogyne spp. populations in the northern coast of Peru. Further long-term surveys are needed to confirm the impact of P. penetrans on nematode regulation and collect isolates for taxonomic, molecular and host-specificity studies.

Root-knot nematodes (RKN) cause extensive damage to grapevine cultivars. RKN-resistant grapevine rootstocks remain vulnerable to biotic and abiotic stresses. This study aimed to determine the influence of composted animal manures (CAMs) [chicken manure (CM), cow manure (CowM), and sheep manure (SM)] with or without plant growth-promoting rhizobacteria (PGPR) on the population of Meloidogyne incognita, free-living nematodes (FLNs) and predaceous nematodes (PNs) residing in the soils of vineyard cultivars (Flame, Superior and Prime). The nematodes were isolated from grapevine roots and rhizosphere soils, then the absolute frequency of occurrence (FO), relative FO, prominence value (PV), and population density (PD) were assessed. The impact of CAMs and PGPR on the growth parameters, fruit output, and quality of three grapevine varieties was subsequently evaluated. Eight treatments included a control without CAMs or PGPR amendments, the CAMs alone, or CAM treatments combined with PGPR. The results showed that FLNs and PNs were more abundant in Prime than Flame or Superior cultivars when poor sandy loam soils were supplied with CAMs. Among all tested manures, CM was the best treatment as a nematicide. This was evident from the decreased numbers of M. incognita and increased numbers of FLNs and PNs in grapevine fields. Compared to the soil-applied oxamyl (a systemic nematicide), which was efficiently suppressive on M. incognita for two months, CM significantly (P < 0.05) decreased PD of the phytonematodes for five months, improved soil structure and enhanced the soil biological activities. There were significant (P < 0.05) increases in the number of leaves/vines by 79.9, 78.8, and 73.1%; and total fruit weight/vine by 76.9, 75.0, and 73.0% in Flame, Superior, and Prime varieties, respectively, compared to untreated vines. Regardless of the cultivar, soils amended with CM + PGPR achieved the lowest number of M. incognita among all other treatments, followed by SM + PGPR and CowM + PGPR. It was concluded that CAMs amendment, mainly CM, along with PGPR in poor sandy soils of temperate areas, is considered a sustainable approach for reducing parasitic nematodes and improving agricultural management.

BACKGROUND Meloidogyne incognita is a highly damaging pathogenic nematode that causes significant annual economic losses. Therefore, the development of reliable biological control agents against M. incognita is imperative. The Bacillus velezensis RKN1111 strain, isolated from inter-root soil, demonstrates the ability to directly kill M. incognita. In this study, we investigated the effect of RKN1111 in inducing resistance to M. incognita in Cucumis sativus and examined changes in the content of immune-responsive substances in the induction-treated cucumber plants. RESULT The RKN1111 treatment reduced the number of root galls in infected cucumbers, with a maximum reduction of 78.19%. RKN1111 stably colonized cucumber roots, reaching 3.65 x 106 CFU/g in 3 days. The approach and infestation rates of M. incognita on RKN1111-induced treated cucumber root tips declined at varying time points. Furthermore, RKN1111 induced significant increases (P < 0.05) in hydrogen peroxide (H2O2) and superoxide anion (O2-) contents, as well as in the callose deposition area in cucumber, by up to 59.84, 83.28, and 61.59%, respectively. CONCLUSION RKN1111 has been demonstrated to stably colonize cucumber root systems and defend against M. incognita infestation by inducing systemic resistance in the host plant. Additionally, RKN1111 elevated the levels of immune-responsive substances in cucumber plants. RKN1111 has great potential for application in the integrated pest management of M. incognita. (c) 2025 Society of Chemical Industry.

Integrating cover crops and bionematicides presents a sustainable approach to managing plant-parasitic nematodes (PPN) in organic vegetable production systems. The integration of sunn hemp, Crotalaria juncea ('Crescent sun') and sorghum-sudangrass, Sorghum bicolor x S. sudanense ('Sweet Six BMR') with bionematicides was evaluated in two locations in central (Gulf Coast Research and Educational Centre-GCREC) and south (Fort Lauderdale Research and Educational Centre-FLREC) Florida for the effectiveness of PPN suppression. Field experiments were conducted with establishing cover crops in each location 3 months before planting organic zucchini on plastic beds equipped with a drip application system used to inject three commercial bionematicides (thyme oil, neem oil and azadirachtin) and the broth culture of Xenorhabdus bovienii bacteria associated with Steinernema feltiae. Cover cropping with sunn hemp and sorghum-sudangrass significantly reduced population densities of root-knot nematodes (Meloidogyne spp.) at GCREC, whereas only sunn hemp reduced the root-knot nematode population at FLREC. Galling severity on zucchini roots caused by Meloidogyne spp. was significantly lower in azadirachtin and neem oil applications integrated with sunn hemp. The impact of integrating cover crops with bionematicides on other PPN, such as Mesocriconema spp., Nanidorus minor and Hoplolaimus spp., varied among the treatments at both locations. Integrating cover crops with bionematicide applications provided additional control options for zucchini, but the efficacy of different bionematicides depended on the nematode species present in the soil and the cover crop species used. These findings underscore the importance of adaptive nematode management, where control strategies are customised to target the specific nematode populations causing economic damage in each field.

The Meloidogyne spp., commonly known as root-knot nematodes (RKN), are obligate sedentary endoparasites considered among the most damaging plant-parasitic nematodes globally. They harm crops by using parasitic proteins to alter host cell physiology, which promotes parasitism and reduces crop yield. Traditional RKN management, primarily through chemical control, negatively impacts the nutritional value, soil texture, and vegetable production, and poses risks to human health and the environment. An emerging eco-friendly and costeffective alternative is the use of plant growth-promoting microbes (PGPM)-mediated biological approaches. The PGPM enhances plant growth directly by solubilizing phosphorus and iron, fixing nitrogen, producing phytohormones, siderophores, and ammonia, or indirectly through competition, antibiosis, hydrogen cyanide, 1-aminocyclopropane-1-carboxylate (ACC) deaminase enzyme, and exopolysaccharides (EPS) production. This review explores various RKN management strategies, emphasizing green biological approaches, their benefits and drawbacks, current commercial status and usage, and the underlying genes, challenges, and limitations associated with these methods.

Storage of nematode-infected soil, roots and nematode suspensions is important in nematological research. The available storage methods are based on potato cyst nematodes, where cysts with viable eggs can be stored for long periods at 4 degrees C. When dealing with other nematode species, understanding the effect of storage temperature is crucial. This study was designed to investigate the decline rate and survival of four root-knot and a lesion nematode of both temperate and tropical origin, when stored at 4 degrees C in three substrates: water, soil and roots. The starting density (P-i ) for each substrate was determined at t = 0 and survival of all nematode species was estimated at 10-day intervals for 100 days. During storage, population densities of all species declined in all substrates exponentially. A slower decline rate (r(d) = 0.988-0.999) was observed for juveniles of Meloidogyne fallax in water, soil and roots compared to juveniles of M. hapla and Pratylenchus penetrans. Meloidogyne incognita was seriously affected by cold storage with the highest decline rate (r(d) = 0.919-0.977) observed in all substrates. Only data on the root substrate were obtained for M. javanica with a decline rate of (r(d) = 0.977) predicting zero survival at t > 100 days. Notable is the higher fraction of surviving P. penetrans (P-i = 0.238-0.545) in all substrates during the storage period, compared with all other species. Based on the results, it is recommended to process nematode samples in the three substrates as quickly as possible, as underestimation of the actual population densities is likely. Consequences of cold storage in handling and processing of samples from different substrates are discussed.

The root-knot nematode (Meloidogyne spp.) is an obligate plant parasite and is one of the largest threats to the Australian sweetpotato industry, causing crop losses of up to 57% of marketable yield. In this study, two potential fungal biocontrol agents were encapsulated in alginate granules and their nematophagous activity was assessed in a laboratory-based microcosm experiment. Both species of fungi significantly reduced numbers of root-knot nematodes in red ferrosol soil. A greater reduction was observed in untreated field soil prior to introduction of root-knot nematodes and fungal biocontrol agents compared to soil that had been heat-sterilised. In a ten-week glasshouse experiment, no significant difference in the root-knot nematode populations in sweetpotato roots and soil was found between fungal biocontrol agent and control treatments. There was a trend towards an increase in the sweetpotato storage root weight and reduction in storage root damage in fungal biocontrol agent compared to control treatments, and both yield and damage levels were similar to those achieved from the use of chemical nematicide treatments. These results demonstrate the need for greater understanding of the interactions between soil biological populations and introduced nematophagous fungi if effective biocontrol is to be consistently achieved with these bioagents under field conditions.

Meloidogyne arenaria (peanut root-knot nematode, PRKN) is an important pest in peanut (Arachis hypogea) production in the United States, including specialty Virginia-type peanuts. Cultivars resistant to PRKN and nematicide application are two available methods for managing PRKN. The objectives of this study were to determine the impacts of resistant Virginia-type peanut cultivars (Georgia-19HP and TifJumbo) on (1) management of PRKN abundances and damage and (2) total free-living nematode soil abundances. A common susceptible cultivar (Bailey II) with or without in-furrow fluopyram nematicide was compared to the resistant cultivars without nematicide in field trials in Florida (2022 and 2023). Resistant cultivars reduced midseason PRKN abundances from roots by 92-98% and final PRKN soil abundances by 81-93% relative to the untreated susceptible cultivar. Fluopyram reduced midseason PRKN root abundances by 65-74% and final PRKN soil abundances by 42-51% relative to untreated susceptible. Although PRKN reproduced on peanuts, no damage symptoms were observed, yield did not vary by treatment in 2022, and yield was significantly greater for fluopyram than either resistant cultivar in 2023. Impacts on total free-living nematode soil abundances were inconsistent. In summary, either fluopyram or resistant cultivars are effective tools for managing PRKN abundances in Virginia-type peanuts.