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Summary: The root-knot nematode, Meloidogyne javanica , is one of the most damaging plant-parasitic nematodes, affecting chickpea and causing substantial yield losses worldwide. The damage potential and population dynamics of this nematode in chickpea in Ethiopia have yet to be investigated. In this study, six chickpea cultivars were tested using 12 ranges of initial population densities (P i) of M. javanica second-stage juveniles (J2): 0, 0.125, 0.25, 0.5, 1, 2, 4, 8, 16, 32, 64 and 128 J2 (g dry soil)−1 in a controlled glasshouse pot experiment. The Seinhorst yield loss and population dynamics models were fitted to describe population development and the effect on different measured growth variables. The tolerance limit (T TFW) for total fresh weight ranged from 0.05 to 1.22 J2 (g dry soil)−1, with corresponding yield losses ranging from 31 to 64%. The minimum yield for seed weight (m SW) ranged from 0.29 to 0.61, with estimated yield losses of 71 and 39%. The 'Haberu' and 'Geletu' cultivars were considered good hosts, with maximum population densities (M) of 16.27 and 5.64 J2 (g dry soil)−1 and maximum multiplication rate (a) values of 6.25 and 9.23, respectively. All other cultivars are moderate hosts for M. javanica ; therefore, it is crucial to initiate chickpea-breeding strategies to manage the tropical root-knot nematode M. javanica in Ethiopia. [ABSTRACT FROM AUTHOR]

In 2022, Jindami was developed as an early maturing mealy sweet potato variety. It was derived from a cross between Dahomi (IT309420) with early maturity and Jinyulmi (IT327287) with early maturity and good palatability. The storage roots of Jindami have a light-purple skin, yellow flesh, and a reverse-ovate shape. When steamed, Jindami storage roots exhibit a mealy texture and are tenderer than those of the check variety, Jinyulmi. The sugar content of steamed Jindami storage roots was 25.4 mg/100 g on a dry weight basis, which was 6.0% higher than that of Jinyulmi. The marketable yield of Jindami storage roots was 28.6 t/ha in the early-season production, which was 19.2% higher than that of Jinyulmi with high yield in the early-season production. Jindami is resistant to root-knot nematode and Fusarium wilt. Jindami is expected to contribute to an increased income for sweet potato-growers as it has good palatability and can be shipped at a time when the market price is high owing to its high yield in the early-season production. [ABSTRACT FROM AUTHOR]

Meloidogyne hispanica infects many economically important crops worldwide and has been listed as a quarantine pest in many countries and as an invasive alien species in China. Accurate identification of this pathogen is essential for the establishment of efficient and sustainable integrated pest management programs. During the field investigations in Hainan, China, we discovered galled roots caused by nematode infestation in the pepper field. Further identification of the nematode isolated from the root galls, including morphological and molecular techniques, confirmed that the isolated population infesting the pepper roots belonged to the species M. hispanica. Upon artificial inoculation under greenhouse conditions, the isolated nematodes induced symptoms that closely resembled those observed in the field. To the best of our knowledge, this is the first documented case of M. hispanica parasitizing pepper crops in China, which will provide valuable basis to formulate targeted control strategies. [ABSTRACT FROM AUTHOR]

Brazil is the largest coffee-producing nation in the world. Over 50% of the national production comes from the Minas Gerais state, with relevant contribution of the region covered by the Cerrado biome. Given the threat posed by root-knot nematodes (RKN, Meloidogyne spp.) to coffee production, we collected plant and soil samples from infested plantations across 16 counties and identified the species of this pathogen. Based on the female perineal patterns, male morphology, esterase phenotypes and SCAR markers, the species found were Meloidogyne exigua, Meloidogyne paranaensis, Meloidogyne incognita and Meloidogyne arenaria. The most prevalent species was M. exigua, occurring in 83.8% of the sampled sites, followed by M. paranaensis (19%) and M. incognita (4.9%). Mixed populations of RKN were observed in 7.7% of the sites, with the highest prevalence of M. exigua + M. paranaensis and M. paranaensis + M. incognita, followed by M. exigua + M. incognita. Meloidogyne arenaria was found in one site, in a mixed population with M. paranaensis + M. exigua. Strategies to prevent the spread of these nematodes to non-infested areas are highly recommended, particularly focusing on the most aggressive species such as M. paranaensis and M. incognita. [ABSTRACT FROM AUTHOR]

The root-knot nematode Meloidogyne enterolobii is a major constraint to pepper production in tropical regions. In the long-term practice of root-knot nematode management, bacterial nematicides have attracted increasing attention as effective biocontrol agents. In this study, we evaluated the efficacy of Bacillus thuringiensis strain 00-50-5 (Bt 00-50-5) against M. enterolobii through in vitro, greenhouse and field trials. The cell-free supernatant of Bt 00-50-5 exhibited potent nematicidal activity against second-stage juveniles (J2s) of M. enterolobii, with mortality rates of 98.0% and 100% after 24 h and 36 h of exposure, respectively. In addition, Bt 00-50-5 showed inhibitory effects on the hatching of M. enterolobii eggs, resulting in a remarkable 96.6% reduction in the egg hatching rate after 6 days compared to the control. The pot trials showed that both pepper root galls and egg masses were reduced, and plant growth was improved after treatment with Bt 00-50-5. The field trials showed that the gall index was significantly reduced, with a 66.3% and 68.2% reduction in disease index in 2020–2021 and 2021–2022, respectively, and pepper yield was improved, with a 96.2% and 93.1% increase in yield in 2020–2021 and 2021–2022, respectively, compared to the control. These results indicate the potential use of Bt 00-50-5 as an effective biocontrol agent against M. enterolobii. [ABSTRACT FROM AUTHOR]

Root-knot nematode disease severely affects the yield and quality of the mandarin variety Citrus reticulata Blanco "Orah" in Guangxi, China. Nevertheless, the pathogen and the effects of this disease on microbial communities remain inadequately understood. This study identified the root-knot nematode Meloidogyne panyuensis in the rhizosphere of infected Orah using morphological and molecular biological methods. Soil chemical properties indicated that organic matter, total nitrogen (TN), total phosphorus (TP), available phosphorus (AP), total potassium (TK), and available potassium (AK) were significantly higher in the rhizosphere soil of M. panyuensis-infected Orah than in that of healthy plants. The relative abundance of the bacteria Bacillus, Sphingomonas, and Burkholderia-Caballeronia-Paraburkholderia, as well as the fungi Lycoperdon, Fusarium, Neocosmospora, Talaromyces, and Tetragoniomyces, was elevated in the rhizosphere soil of M. panyuensis-infected plants. Furthermore, organic matter, TN, available nitrogen (AN), TP, AP, TK, and AK exhibited positive correlationswith these bacteria and fungi in the rhizosphere soil of M. panyuensis-infected Orah. Potential biocontrol strains, such as Burkholderia spp., were identified by comparing the differences in rhizosphere microbial composition between healthy Orah and M. panyuensis-infected Orah. Our findings provide a foundation for the early warning and prevention of root-knot nematode disease in Orah. [ABSTRACT FROM AUTHOR]

Effect of different organic amendments (oil cakes, manures, and plant leaves) with Fictor composticola was evaluated against root-knot nematode, Meloidogyne incognita. Organic amendments @ 15 g/kg soil were mixed in pots containing 1 kg sterilized soil. Cucumber (cv. CCH-1) plants grown in these pots were inoculated with 2000 J2 of Meloidogyne incognita and 400 F. composticola per pot, after one week of germination. Root-knot nematode population significantly declined by different organic amendments in the presence of F. composticola. F. composticola with neem cake had the maximum plant weight among all amendments, but maximum root-knot nematode population reduction was recorded in F. composticola with Farm Yard Manure (FYM) followed by F. composticola with neem leaves. Among all organic amendments, the maximum population of F. composticola was found in chicken manure followed by vermicompost. These results indicate that organic amendments can be applied with predatory nematode, Fictor composticola as a promising alternative against M. incognita in cucumber in India. [ABSTRACT FROM AUTHOR]

In vitro bio-assays were conducted to investigate the impact of a newly developed nano-formulation of Pochonia chlamydosporia, a fungus parasitic to the eggs and females of the root-knot nematode Meloidogyne incognita, which infects carrots. Second-stage juveniles (J2) and eggs of M. incognita were exposed to varying concentrations of the P. chlamydosporia nano-formulation (PCNF) ranging from 0.025 to 0.5% (0.25, 0.50, 1.0, 2.5 and 5.0 mL/L). Results demonstrated that PCNF exhibited antagonistic effects against M. incognita J2, with its activity increasing in proportion to both concentration and exposure time. Complete mortality of J2 was observed at a concentration of 5.0 mL/L after 96 h of exposure. At the same dose, PCNF parasitized 100% of M. incognita eggs. Subsequently, glasshouse bioassays were conducted to assess the effectiveness of different PCNF concentrations as a soil treatment in tomato plants challenged with M. incognita. Soil drenching with PCNF significantly reduced J2 density in soil (60.0–67.9%) and female density in roots (58.7–73.4%), along with reduced root-gall indices (2.1–3.1). Additionally, 61.0–87% eggs and 57.7–77.8% females were parasitized by P. chlamydosporia in carrot plants. Across concentrations from 0.25 to 5.0 mL/L, PCNF showed significant effectiveness in controlling M. incongnita pathogenesis in carrot. Further studies are recommended to evaluate the stability, shelf life and toxicity of PCNF before validating its use against natural M. incognita populations in field conditions. [ABSTRACT FROM AUTHOR]

The following study aimed to evaluate the effect of three plant growth-promoting bacteria: Bacillus amyloliquefaciens, Pseudomonas fluorescens and Streptomyces griseoviridis, and two types of fertilization: chemical and organic (vermicompost) in the soil for the control of root-knot nematode (Meloidogyne sp.), and their effect on the development of chili crops in the greenhouse. Four fertilizations, both chemical and organic, were carried out at the time of transplant and at 15, 30, and 45 days after transplant. The trial lasted five months. A total of nine treatments were established (three types of bacteria + one chemical control × two types of fertilization + one control with water), each of them with four replications, for a total of 36 plants. Measurements of galling percentage (GP) and galling index (GI) were made, and the efficiency of the treatments was determined. The dry and fresh weights of both the aerial part and the root of the plants were also determined. The highest degree of damage occurred in the control treatment with 71.2% GP, while the lowest GP was observed in the chemical fertilization × B. amyloliquefaciens treatment. The GI did not present significant differences between treatments because the negative effect of galling was counteracted by adequate root growth, which was especially visible in treatments such as chemical fertilization × B. amyloliquefaciens and organic fertilization × oxamyl. [ABSTRACT FROM AUTHOR]

Background: Abamectin (ABA) is considered a powerful insecticidal and anthelmintic agent. It is an intracellular product of Streptomyces avermitilis; is synthesized through complicated pathways and can then be extracted from mycelial by methanol extraction. ABA serves as a biological control substance against the root-knot nematode Meloidogyne incognita. This investigation is intended to reach a new strain of S. avermitilis capable of producing ABA effectively. Results: Among the sixty actinobacterial isolates, Streptomyces St.53 isolate was chosen for its superior nematicidal effectiveness. The mycelial-methanol extract of isolate St.53 exhibited a maximum in vitro mortality of 100% in one day. In the greenhouse experiment, the mycelial-methanol extract demonstrated, for the second-stage juveniles (J2s), 75.69% nematode reduction and 0.84 reproduction rate (Rr) while for the second-stage juveniles (J2s), the culture suspension demonstrated 75.38% nematode reduction and 0.80 reproduction rate (Rr). Molecular identification for St.53 was performed using 16 S rRNA gene analysis and recorded in NCBI Genbank as S. avermitilis MICNEMA2022 with accession number (OP108264.1). LC-MS was utilized to detect and identify abamectin in extracts while HPLC analysis was carried out for quantitative determination. Both abamectin B1a and abamectin B1b were produced and detected at retention times of 4.572 and 3.890 min respectively. Conclusion: Streptomyces avermitilis MICNEMA2022 proved to be an effective source for producing abamectin as a biorational agent for integrated nematode management. [ABSTRACT FROM AUTHOR]

The Mi-1.2 gene confers resistance to a wide range of Meloidogyne species, being the most important resistance factor employed in tomato breeding so far. However, many aspects related to the interaction of Mi-1.2-carrying tomato cultivars and virulent/avirulent Meloidogyne populations have not yet been clarified. Herein, comparative histopathological analyses were carried after inoculation of the homozygous (Mi-1.2/Mi-1.2) tomato rootstock 'Guardião' and the susceptible cultivar 'Santa Clara' (mi-1.2/mi-1.2) with virulent and avirulent populations of M. javanica. In the susceptible control, it was possible to visualize second stage juveniles (J2) of avirulent population and feeding sites from 2 to 30 days after infection (DAI) with females reaching maturity at 24-34 DAI. In the resistant rootstock, the Mi-1.2 gene-mediated resistance was related mainly to early defense responses (pre-infection and hypersensitive reaction), which led to an immunity-like phenotype that completely prevented the reproduction of the avirulent Meloidogyne population. On the other hand, J2s of the virulent M. javanica population were able to penetrate roots much more than the avirulent population, migrated and developed normally, showing intense and similar pattern of penetration from 4 to 34 DAI in the root tissues of both resistant and susceptible tomato genotypes. The total numbers of J2, J3, J4, and females counted in 'Santa Clara' for the virulent population of M. javanica were higher than in 'Guardião'. [ABSTRACT FROM AUTHOR]

The root-knot nematodes (Meloidogyne spp.) are one of the most dangerous and widespread species of nematodes affecting tomatoes. There are few methods for controlling nematodes in tomatoes. Natural resistance is important in conferring resistance against nematodes. A study was conducted to evaluate the reaction of tomato accessions to root-knot nematode Meloidogyne arenaria (Neal) Chitwood. Twenty one tomato accessions were subjected for screening. Susceptible tomato variety Ideal was used as control. The tomato plants were evaluated 60 days after inoculation on the basis of the gall index (GI), egg mass index (EMI), final populations (Pf) and reproduction factors (Rf). All the tomato accessions show varying degree of response. Most of the screened accessions were susceptible to M. arenaria, six were resistant and two accessions showed hypersensitive reaction. [ABSTRACT FROM AUTHOR]

Background: Plant-growth-promoting rhizobacteria (PGPR) are a class of beneficial bacteria that colonise the roots of plants and improve projected plant growth through a multivariate process. PGPR application is increasing steadily in the field of agriculture, providing an attractive mechanism to replace pesticides, chemical fertilisers and additional supplements. Methods: In this study, PGPR from rhizospheric soil collected from Abha, a city located in the southern region of the Kingdom of Saudi Arabia (KSA), were isolated and characterised to facilitate verifying the efficacy of using PGPR as a biological control to improve fava bean growth. Four bacterial isolates from the nodules of fava bean plants, S4, S5, S6 and S17, were isolated and characterised. Consequently, an investigation highlighting the impact of PGPR isolates on the preservation of fava bean plants from the root-knot nematode was conducted through a pot culture experiment. Soil infested with the nematode was added to the pots. Two commercial types of fava bean plants (Vicia faba L.) were co-inoculated with PGPR 15 days after planting. Result: The results reveal that the nodule-forming bacteria interact synergistically; this was evidenced by a prominent increase in the shoot length and dry weight of the fava bean plants that had been cultivated in the nematode-infested soil. The results also demonstrate that the overall treatment of the plants did not lead to nodule formation. The results indicate that nodule-forming bacteria could be utilised in leguminous crops to facilitate biocontrol of the root-knot nematode. [ABSTRACT FROM AUTHOR]

Direct-seeded rice (DSR) is gaining popularity among farmers due to its environmentally safe and resource-efficient production system. However, managing the rice root-knot nematode (RRKN), Meloidogyne graminicola, remains a major challenge in DSR cultivation. Developing genetic resistance is a pragmatic and effective approach compared to using hazardous pesticides. Pusa Basmati 1121 (PB1121) is the most popular Basmati rice variety, but it is highly susceptible to RRKN. In contrast, Phule Radha (PR) has shown highly resistant reaction to RRKN, as reported in our earlier study. We generated an F2:3 population from the cross of PB1121/PR and evaluated it for RRKN resistance-related traits under artificial inoculation conditions. The distribution pattern of traits in the F2:3 population indicated that resistance may be governed by a few major-effect genes and many minor-effect genes. The molecular markers reported to be associated with QTLs governing RRKN resistance traits were used to test in the current population. Although the simple linear regression identified significant associations between the markers and RRKN resistance-associated traits, these associations were spurious as the LOD score was below the threshold limit. This indicates that PR possesses novel genomic regions for resistance to RRKN as it does not possess any of the earlier reported QTLs. [ABSTRACT FROM AUTHOR]

This study aimed to assess the effects of rock dust on Meloidogyne javanica in soybean grown in autoclaved and non-autoclaved soil and investigate the impacts on plant foliar nutrition. The nematode reproduction experiment was conducted in two periods (Trials 1 and 2) in a 5 × 2 factorial design (rock dust rates of 0, 1000, 2000, 3000, and 4000 kg ha−1 × autoclaved and non-autoclaved soil). Soybean were inoculated with 2000 eggs + second-stage juveniles (J2) of M. javanica, and nematode and vegetative variables were evaluated at 60 days after inoculation (DAI). The penetration experiment followed a 2 × 2 factorial design (rock dust rates of 0 and 2500 kg ha−1 × autoclaved and non-autoclaved soil). Soybean were inoculated with 2000 eggs + J2 of M. javanica and evaluated at 5, 10, 15, 20, and 25 DAI. The shoot dry biomass from the reproduction experiment (Trial 1) was analyzed for macro- and micronutrients. In Trial 1, nematode reproduction decreased proportionally to the increase in rock dust rate in non-autoclaved soil. In Trial 2, the lowest nematode numbers were predicted to be achieved with rates of 2213 to 2309 kg ha−1, and nematode numbers were lower in autoclaved than in non-autoclaved soil. Rock dust reduced J2 penetration at 10 and 15 DAI, and there was no formation of females in treated plants. Rock dust application increased foliar levels of Fe, B, and Cu. Rock dust reduced M. javanica reproduction, penetration, and development in soybean and promoted gains in Fe, Cu, and B foliar contents. [ABSTRACT FROM AUTHOR]

Root‐knot nematodes (RKNs) are one of the most serious pests of carrot plants. Resistance cultivars are a cost‐effective and ecofriendly management strategy for nematodes. To develop these, it is essential to understand the genetic, molecular and biochemical aspects underpinning RKN infection. Here, Meloidogyne javanica penetration and development, defence reactions and antioxidant enzyme activity were investigated in a resistant carrot cultivar (TN‐99‐129) compared to the susceptible cultivar TN‐99‐62. No significant difference was found in the number of J2s penetrating the roots of both cultivars. At 2 days post‐inoculation (DPI), necrosis symptoms were observed around the head of penetrated nematodes. Cell death also increased in the roots of the nematode‐infected TN‐99‐129 cultivar. Callose deposition happened at 6 DPI, and lignin content increased with delay (21 DPI) in the inoculated resistant cultivar. In addition, the reactive oxygen species metabolism process in resistant and susceptible cultivars was significantly different. In TN‐99‐129, catalase activity inhibition was observed at the early (2 DPI) phases of infection, and increasing superoxide dismutase activity and a relative decrease in catalase activity during nematode development. The activity of guaiacol peroxidase also increased significantly in the resistant cultivar, but no significant difference was observed in the activity of ascorbate peroxidase. This study explains the process of defence reactions in the TN‐99‐129 carrot cultivar during RKN penetration and development. The exhaustive characterization of the defence mechanism of a novel source of resistance to RKN in carrots constitutes a significant step toward their use in crop breeding. [ABSTRACT FROM AUTHOR]

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Plant-parasitic nematodes are a major problem for horticultural production, causing significant economic losses. Chemical nematicides are a common nematode control strategy but can negatively impact the environment and human health. In this review, we provide an overview of the use of fungi for the biological control of plant-parasitic nematodes in horticultural crops. Fungal bio-control represents an alternative, environmentally friendly strategy for managing nematodes. The use of fungi for the bio-control of nematodes has gained increasing attention due to the potential benefits of selectivity, sustainability, and long-term control. Here, we discuss the different types of fungi used for nematode management, the mechanisms of their action, the advantages and limitations of using fungi for bio-control, and the factors affecting their efficacy. Additionally, we provide several case studies of fungal bio-control against root-knot, cyst, and lesion nematodes in horticultural crops. The review concludes with a discussion of future directions and research recommendations for implementing fungal bio-control in horticultural crops. [ABSTRACT FROM AUTHOR]

This paper mainly reveals the dhynamic occurrence rule of root-knot nematode in the vegetable soil of Chifeng protected area, and provides a theoretical basis for the control of southern root-knot nematode disease in this area. The dynamic change of root-knot nematode quantity in the soil of Chifeng protected land was monitored for 10 years. The dynamic change law of the lateral and vertical distribution of root-knot nematode in the soil from 2013 to 2014 was investigated. The dynamic occurrence law of the southern root-knot nematode under different years and agronomic measures was expounded. The results showed that the lateral distribution of southern root-knot nematodes in greenhouse soil was as follows: the northern and central nematodes were the most abundant, while the southern nematodes were the least abundant. The vertical distribution of nematodes was as follows; the southern root-knot nematodes distributed most in the 4-15 cm soil layer, and less in the 15-25 cm soil layer. During the 10 years of monitoring sites, the occurrence rule of southern root-knot nematodes was as follows: about 6 generations occurred every year in greenhouses of monitoring sites, and each crop occurred about 3 generations. In terms of quantity, the maximum number of root-knot nematodes appeared around May and November every year, and the number of overwinter stubble was greater than that of autumn stubble. The distribution and dynamic occurrence of southern root-knot nematode in soil were studied, which can provide theoretical guidance for the prevention and control of root-knot nematode disease in Chifeng area. [ABSTRACT FROM AUTHOR]

Background: Meloidogyne incognita is one of the most important plant-parasitic nematodes and causes tremendous losses to the agricultural economy. Light is an important living factor for plants and pathogenic organisms, and sufficient light promotes root-knot nematode infection, but the underlying mechanism is still unclear. Results: Expression level and genetic analyses revealed that the photoreceptor genes PHY, CRY, and PHOT have a negative impact on nematode infection. Interestingly, ELONGATED HYPOCOTYL5 (HY5), a downstream gene involved in the regulation of light signaling, is associated with photoreceptor-mediated negative regulation of root-knot nematode resistance. ChIP and yeast one-hybrid assays supported that HY5 participates in plant-to-root-knot nematode responses by directly binding to the SWEET negative regulatory factors involved in root-knot nematode resistance. Conclusions: This study elucidates the important role of light signaling pathways in plant resistance to nematodes, providing a new perspective for RKN resistance research. [ABSTRACT FROM AUTHOR]

In the present study, biocontrol potential of Bacillus subtilis CRB7 was evaluated to counter root-knot nematode infestation in tomato grown under protected cultivation. Under pot conditions, gall formation on roots was reduced when B. subtilis CRB7 applied at 1.25, 2.5 and 5 g plant−1. Nursery drench with B. subtilis CRB7 at 5, 10 and 15 g m−2 significantly reduced gall formation on roots (37.0 to 85.8%). Further, application of B. subtilis CRB7 as nursery drench at 15 g m−2, soil drench at 0.5% at 30 day's interval and soil application of enriched vermicompost (5 kg 2 tonnes−1 of vermicompost ha−1) significantly reduced gall formation on roots (58.3% and 54.2%) and enhanced yield (29.8% and 15.4%) in two consecutive protected field experiments, respectively. Given its potent efficacy, B. subtilis CRB7 emerges as a promising component for the management of root-knot nematode in tomato grown under protected cultivation. [ABSTRACT FROM AUTHOR]

Root‐knot nematodes (RKNs) are microscopic parasitic worms able to infest the roots of thousands of plant species, causing massive crop yield losses worldwide. They evade the plant's immune system and manipulate plant cell physiology and metabolism to transform a few root cells into giant cells, which serve as feeding sites for the nematode. RKN parasitism is facilitated by the secretion in planta of effector molecules, mostly proteins that hijack host cellular processes. We describe here a conserved RKN‐specific effector, effector 12 (EFF12), that is synthesized exclusively in the oesophageal glands of the nematode, and we demonstrate its function in parasitism. In the plant, MiEFF12 localizes to the endoplasmic reticulum (ER). A combination of RNA‐sequencing analysis and immunity‐suppression bioassays revealed the contribution of MiEFF12 to the modulation of host immunity. Yeast two‐hybrid, split luciferase and co‐immunoprecipitation approaches identified an essential component of the ER quality control system, the Solanum lycopersicum plant bap‐like (PBL), and basic leucine zipper 60 (BZIP60) proteins as host targets of MiEFF12. Finally, silencing the PBL genes in Nicotiana benthamiana decreased susceptibility to Meloidogyne incognita infection. Our results suggest that EFF12 manipulates PBL function to modify plant immune responses to allow parasitism. [ABSTRACT FROM AUTHOR]

Meloidogyne enterolobii is regarded as one of the most severe and threatening pathogens worldwide. Guava production in India is quenched by the invasion of root-knot nematode, Meloidogyne enterolobii. Bacterial bio-control agents confer resistance against nematodes by producing various bioactive molecules. Exploiting these biomolecules will lead to the development of novel nematicidal formulations for managing plant parasitic nematodes. Considering this, our present investigation was focused on the isolation and identification of endophytic bacterial communities from wild guava Psidium eugeniaefolia. Amongst various endophytes, Bacillus subtilis GEB-1 exhibited a 90% reduction in the population of M. enterolobii. Cell-free supernatant extracts of B. subtilis GEB-1 revealed the presence of seventeen unique biomolecules. Attempts were made to dock these biomolecules against major protein targets of M. enterolobii such as E3 ubiquitin ligase, Neurotransmitter-gated ion-channel, G protein-coupled receptor kinase, Peptidase M12B domain-containing protein, Hyaluronidase through molecular docking techniques. The results of in-silico studies revealed that all seventeen biomolecules had a significant impact on protein targets of M. enterolobii. Among other bacterial metabolites, 2-heptanone and 2,3-butanediol were found to have a greater binding affinity with protein targets of M. enterolobii. Furthermore, the in-vitro evaluation of 2-heptanone and 2,3-butanediol at different concentrations confirmed their nematicidal activity against eggs and second-stage juveniles of M. enterolobii. Hence our present study revealed that bacterial metabolites, 2 heptanone, and 2,3-butanediol can be explored as novel nematicidal molecules against guava root-knot nematodes, M. enterolobii. [ABSTRACT FROM AUTHOR]

This study provides the first report of a quantitative trail locus (QTL) in maize (Zea mays) for resistance to the southern root-knot nematode (SRKN) (Meloidogyne incognita). The SRKN can feed on the roots of maize in the U.S. Southern Coastal Plain region and can cause yield losses of 30% or more in heavily infested fields. Increases in SRKN density in the soil may reduce the yield for subsequently planted susceptible crops. The use of maize hybrids with resistance to SRKN could prevent an increase in SRKN density, yet no genetic regions have been identified that confer host resistance. In this study, a B73 (susceptible) x Ky21 (resistant) S5 recombinant inbred line (R1L) population was phenotyped for total number of eggs (TE) and root weight. This population had been genotyped using single-nucleotide polymorphisms (SNPs). By utilizing the SNP data with the phenotype data, a single QTL was identified on chromosome 5 that explained 15% of the phenotypic variation (PV) for the number of eggs and 11 % of the P V for the number of eggs per gram of root (EGR). Plants that were homozygous for the Ky2l allele for the most associated marker PZA03172.3 had fewer eggs and fewer EGR than the plants that were homozygous or heterozygous for the B73 allele. Thus, the first QTL for SRKN resistance in maize has been identified and could be incorporated into maize hybrids. [ABSTRACT FROM AUTHOR]

The identification of novel drug targets in plant-parasitic nematodes (PPNs) is imperative due to the loss of traditional nematicides and a lack of replacements. Chemosensation, which is pivotal for PPNs in locating host roots, has become a focus in nematode behavioral research. However, its underlying molecular basis is still indistinct in such a diverse group of PPNs. To characterize genes participating in chemosensation in the Javanese root-knot nematode Meloidogyne javanica, RNA-sequencing of the second-stage juveniles (J2s) treated with tomato root exudate (TRE) for 1 h and 6 h was performed. Genes related to chemosensation in M. javanica mainly responded to TRE treatment at 1 h. Moreover, a gene ontology (GO) analysis underscored the significance of the neuropeptide G protein-coupled receptor signaling pathway. Consequently, the repertoire of putative neuropeptides in M. javanica, including FMRFamide-like peptides (FLPs), insulin-like peptides (ILPs), and neuropeptide-like peptides (NLPs), were outlined based on a homology analysis. The gene Mjflp-14a, harboring two neuropeptides, was significantly up-regulated at 1 h TRE treatment. Through peptide synthesis and J2 treatment, one of the two neuropeptides (MjFLP-14-2) was proven to influence the J2 chemotaxis towards tomato root tips. Overall, our study reinforces the potential of nematode neuropeptides as novel targets and tools for root-knot nematode control. [ABSTRACT FROM AUTHOR]

We present the chromosome-scale genome assembly of the allopolyploid root-knot nematode Meloidogyne javanica. We show that the M. javanica genome is predominantly allotetraploid, comprising two subgenomes, A and B, that most likely originated from hybridisation of two ancestral parental species. The assembly was annotated using full-length non-chimeric transcripts, comparison to reference databases, and ab initio prediction techniques, and the subgenomes were phased using ancestral k-mer spectral analysis. Subgenome B appears to show fission of chromosomal contigs, and while there is substantial synteny between subgenomes, we also identified regions lacking synteny that may have diverged in the ancestral genomes prior to or following hybridisation. This annotated and phased genome assembly forms a significant resource for understanding the origins and genetics of these globally important plant pathogens. Author summary: Root-knot nematodes represent one of the most significant crop parasites globally. Despite their agricultural importance, only limited genomic resources have been published to date, leaving a gap in the understanding of genetic mechanisms driving genome evolution and crop virulence. Here, we have used modern genomic and bioinformatic approaches to create a chromosome-scale reference assembly to investigate the origins and genomic composition of the root-knot nematode species Meloidogyne javanica. This species has an allopolyploid genome, reproduces by ameiotic parthenogenesis and is among the most damaging plant parasitic nematodes with a large and expanding plant host range. Utilising modern long-read DNA sequencing and bioinformatics approaches, we successfully phased the assembly into its constituent subgenomes, a first for this agriculturally important clade. While we find the genomic landscape is mostly syntenic between subgenomes, we identified regions of minimal similarity, and highlight structural divergence between subgenomes. [ABSTRACT FROM AUTHOR]

Studies were conducted to assess the crop loss in Coleus, Plectranthus rotundifolius, a short duration tuber yielding vegetable, due to infestation of root knot nematode, Meloidogyne incognita. Plants inoculated with 5000 J2 showed 50.78% reduction in the yield of coleus. Five local collections (Alur, Mankada, TCM-9, M-131 and Pulamanthol) and two improved varieties (Sree Dhara and Nidhi) were screened for relative tolerance to M. incognita. Local collection, Alur showed significant superiority in reducing the nematode population in soil and root. Lowest root-knot index (1.00) and reproduction factor (0.39) was recorded by the Alur collection compared to improved varieties. Defence enzyme activity and phenolic content in the resistant variety Alur collection was significantly higher than the improved varieties. Considering the ability to resist nematodes and yield potential, the local variety Alur collection can be used in breeding programmes to develop high yielding nematode resistant varieties suitable for cultivation in Kerala. [ABSTRACT FROM AUTHOR]

Background: The role of soil solarization in suppression of soil borne pathogens and weeds has been established by several researchers around the globe It involves capturing solar radiations when the soil receives the maximum sunlight in May-June using a polythene mulch. Its effectiveness depends on ambient temperature, duration of the treatments and soil moisture. This not only acts as a soil disinfectant but also as soil decontamination. It includes various changes in the soil like physical, chemical and biological properties. Methods: The field to lab and vice-versal based investigations were carried during 2021-2022 at Amity Centre for Biocontrol and Plant Disease Management, Amity University, Uttar Pradesh, Noida and identified tomato nurseries of district G B Nagar where heavy infestation (10-12 J2/cc soil) of root knot nematode, Meloidogyne incognita (Kofoid and White) Chitwood was recorded. The treatments comprised of sustainable components viz. deoiled seed cake of neem, a Arbuscular Mycorrhizal fungus Glomus intraradices and indigenous fungal strain of Trichoderma harzianum, (Th7) alone and together applied for evolving IPM module at solarized and unsolarized sets. Under microplot trials, the entire solarized treatments were carried out measuring 3 x 1 sq. meter each in which one set of all the treatments including control covered with clear transparent polythene sheet (400 µ gauge) for solarization. The treatments were replicated thrice in randomized block design. Result: The observations of solarized and unsolarized treatments clearly revealed that the soil solarization in treatments where the sun radiant energy was trapped by 400 µ transparent polysheets significantly reduced the root knot nematode Meloidogyne incognita population both in root and soil in comparison to unsolarized treatments where no solar energy trapping was done. The combined application of locally isolated Trichoderma harzianum (Th7) and VA mycorrhiza, Glomus intraredices enhanced germination and plant growth in nurseries. In the present investigation, the solarized IPM module-4 comprising of other sustainable components viz. neem oil-seed cake, T. harzianum (Th-7) and Arbuscular Mycorrhizal (AM) fungus G. intraredices is proved to be an ideal one in rootknot nematode pest management in tomato nurseries. [ABSTRACT FROM AUTHOR]

SUMMARY: Meloidogyne incognita is one of the most widely distributed plant‐parasitic nematodes and causes severe economic losses annually. The parasite produces effector proteins that play essential roles in successful parasitism. Here, we identified one such effector named MiCE108, which is exclusively expressed within the nematode subventral esophageal gland cells and is upregulated in the early parasitic stage of M. incognita. A yeast signal sequence trap assay showed that MiCE108 contains a functional signal peptide for secretion. Virus‐induced gene silencing of MiCE108 impaired the parasitism of M. incognita in Nicotiana benthamiana. The ectopic expression of MiCE108 in Arabidopsis suppressed the deposition of callose, the generation of reactive oxygen species, and the expression of marker genes for bacterial flagellin epitope flg22‐triggered immunity, resulting in increased susceptibility to M. incognita, Botrytis cinerea, and Pseudomonas syringae pv. tomato (Pst) DC3000. The MiCE108 protein physically associates with the plant defense protease RD21A and promotes its degradation via the endosomal‐dependent pathway, or 26S proteasome. Consistent with this, knockout of RD21A compromises the innate immunity of Arabidopsis and increases its susceptibility to a broad range of pathogens, including M. incognita, strongly indicating a role in defense against this nematode. Together, our data suggest that M. incognita deploys the effector MiCE108 to target Arabidopsis cysteine protease RD21A and affect its stability, thereby suppressing plant innate immunity and facilitating parasitism. [ABSTRACT FROM AUTHOR]

Background and aims: The false-root knot nematode (Nacobbus spp.) comprises polyphagous species, with pepper (Capsicum annuum) being one of the most affected crops. Due to the lack of resistant pepper genotypes, we compared the responses of different commercial cultivars to identify possible plant defence mechanisms against N. celatus. M&M: Nematodes from Río Cuarto (Córdoba Province) and Lisandro Olmos (Buenos Aires Province) were inoculated on pepper cultivars: California Wonder (control), Fyuco INTA, Yatasto, and Fenomeno RZ. Plants were grown under a greenhouse and galls were analysed by histopathological techniques. Results: The roots of the commercial cultivars showed the typical morpho-anatomical alterations induced by N. celatus: gall formation, hyperplasia reactions, development of syncytia in the central cylinder and disorganisation of vascular tissues. Syncytial cells in contact with females of nematodes from Lisandro Olmos showed a defence reaction by Fyuco INTA, whereas feeding sites in Fenomeno RZ did not denote high metabolic activity in nematodes of both origins. Conclusions: The different responses observed between populations and/or hosts demonstrate the importance of considering nematodes from different geographical origins when testing plant material for tolerance and/or resistance to N. celatus. Studies of this nature are necessary since they facilitate a more in-depth understanding of the parasite-plant interaction. [ABSTRACT FROM AUTHOR]

Sixty-six accessions including 11 Solanum species and eight accessions intermediate between S. melongena and S. insanum were screened against root-knot nematode, Meloidogyne incognita, for identification of sources of resistance. Accession of S. insanum (IC316278) and the intermediate between S. melongena and S. insanum accession (IC253952) were found to be moderately resistant (RKI: 3, 11-30 galls per root system) in initial screening, and were found susceptible when these were exposed to M. incoginta for a period of 90 days. However, accession of S. torvum was found to be resistant, as it consistently recorded less number of galls and egg masses after 45 days (7.0 galls and 4.6 egg masses per root system) and 90 days (8.4 galls and 6.6 egg masses per root system) post-inoculation of M. incognita. Thus, it can be concluded that S. torvum accession, IC618029, is a valuable source of resistance to M. incognita which can be used in nematode resistance breeding programme and as a rootstock particularly in brinjal and tomato to lessen nematode damage. [ABSTRACT FROM AUTHOR]

Nemafric-BL phytonematicide is a potent plant-based nematicide which consistently suppress nematode population densities of root-knot (Meloidogyne species) nematodes on various crops, but with limited information on its effects on foliar nutrient elements in sweet potato. The objective of this study, therefore, was to investigate the effects of Nemafric-BL phytonematicide on accumulation of nutrient elements in leaf tissues of sweet potato cv. ‘Bophelo’ under greenhouse conditions in Limpopo Province, South Africa, during autumn (February-April) in 2021 and validated in 2022. The product was applied weekly at geometric concentrations, with mature leaves collected and prepared for analysis of nutrient elements at eight weeks. Seasonal interactions were not significant and therefore data were pooled (n = 70) and then subjected to the Curvefitting Allelochemical Response Dose (CARD) algorithm computer model. Iron (R² = 0.86), K (0.91) and Na (0.82) versus Nemafric-BL phytonematicide each exhibited negative quadratic relations, whereas Zn (0.83) versus the product exhibited positive quadratic relations. In all test elements, the CARD-generated biological indices illustrated that the accumulation of elements was highly sensitive to the concentration of Nemafric-BL phytonematicide. In conclusion, in sweet potato production, the application of NemafricBL phytonematicide can inhibit (Fe, K) and stimulate (Zn) the accumulation of certain elements in leaf tissues of sweet potato cv. ‘Bophelo’. [ABSTRACT FROM AUTHOR]

Background: Green nanoparticles are considered to be an effective strategy for improving phytochemicals and raising productivity in soil infected by root-knot nematodes. This work aims to understand the characteristics of certain nanomaterials, including non-iron (nFe), green non-iron (GnFe), and green magnetic nanobiochar (GMnB), and the effect of adding them at 3 and 6 mg kg− 1 on phytochemicals and tomato (Solanum lycopersicum) plant growth in soils infected by root-knot nematodes. Results: Spectroscopic characterization of nanomaterials showed that nFe, GnFe, and GMnB contained functional groups (e.g., Fe-O, S-H, C-H, OH, and C = C) and possessed a large surface area. Application of GMB at 6 mg kg− 1 was the most efficient treatment for increasing the phytochemicals of the tomato plant, with a rise of 123.2% in total phenolic, 194.7% in total flavonoids, 89.7% in total carbohydrate, 185.2% in total free amino acids, and 165.1% in total tannin compared to the untreated soil. Tomato plant growth and attributes increased with increasing levels of soil nano-amendment in this investigation. The addition of GnFe3 and GnFe6 increased the reduction of root galls of root-knot nematodes by 22.44% and 17.76% compared with nFe3 and nFe6, respectively. The inclusion of the examined soil nano-amendments increased phytochemicals and reduced the total number of root-knot nematodes on tomato plants at varying rates, which played a significant role in enhancing tomato growth. Conclusions: In conclusion, treating tomato plants with GnFe or GMnB can be used as a promising green nanomaterial to eliminate root-knot nematodes and increase tomato yield in sandy clay loam soil. [ABSTRACT FROM AUTHOR]

Root-knot nematodes are polyphagous parasitic nematodes that cause severe losses in the agriculture worldwide. They enter the root in the elongation zone and subtly migrate to the root meristem where they reach the vascular cylinder and establish a feeding site called gall. Inside the galls they induce a group of transfer cells that serve to nurture them along their parasitic stage, the giant cells. Galls and giant cells develop through a process of post-embryogenic organogenesis that involves manipulating different genetic regulatory networks within the cells, some of them through hijacking some molecular transducers of established plant developmental processes, such as lateral root formation or root regeneration. Galls/giant cells formation involves different mechanisms orchestrated by the nematode's effectors that generate diverse plant responses in different plant tissues, some of them include sophisticated mechanisms to overcome plant defenses. Yet, the plant-nematode interaction is normally accompanied to dramatic transcriptomic changes within the galls and giant cells. It is therefore expected a key regulatory role of plant-transcription factors, coordinating both, the new organogenesis process induced by the RKNs and the plant response against the nematode. Knowing the role of plant-transcription factors participating in this process becomes essential for a clear understanding of the plant-RKNs interaction and provides an opportunity for the future development and design of directed control strategies. In this review, we present the existing knowledge of the TFs with a functional role in the plant-RKN interaction through a comprehensive analysis of current scientific literature and available transcriptomic data. [ABSTRACT FROM AUTHOR]

The nematicidal potential of the yeast Papiliotrema terrestris strain PT22AV (YSY) was investigated against the root nematode (RKN) Meloidogyne incognita in in vitro bioassays on infective juveniles (J2) and experiments on tomatoes in pot and greenhouse conditions. The J2 nematodes were exposed to YSY solutions for 19 days, using abamectin (ABA), fosthiazate (FOS) and distilled water as controls. In the experiments on potted and greenhouse tomatoes, 0.5 and 1 kg ha−1 doses of YSY were tested in comparison to ABA, biocontrol agents Purpureocillium lilacinus strain 251 (PUL) and Bacillus firmus strain 1-1582 (BAF), a plant biostimulant/fertilizer (ERG) and the nematicide Fluopyram (FLU). J2's viability was affected by YSL after 7 days, decreasing to zero on the 15th exposure day, while ABA and FOS resulted in 83 and 100% J2 mortality within 24 h. Only the 1.0 kg ha−1 dose of YSY was able to significantly reduce the final nematode population in soil and gall formation on tomato roots, without significant differences from PUL and BAF. All treatments in comparison also resulted in a significant increase in tomato growth and crop yield, except for 0.5 kg ha−1 of YSY. Data indicated that YSY could represent an additional tool for organic and integrated RKN management. [ABSTRACT FROM AUTHOR]

'Georgia‐23RKN' (Reg. no. CV‐158, PI 704578) is a new high‐yielding, normal‐oleic, Tomato spotted wilt virus (TSWV)‐ and root‐knot nematode (RKN) [Meloidogyne arenaria (Neal) Chitwood race 1]‐resistant, medium‐large seeded, runner‐type peanut (Arachis hypogaea L. subsp. hypogaea var. hypogaea) cultivar that was released by the Georgia Agricultural Experiment Station in 2023. It was developed at the University of Georgia, Tifton Campus. Georgia‐23RKN originated from a cross made between 'Tifguard' × 'Georgia Green'. Tifguard is a normal‐oleic, TSWV‐ and RKN‐resistant runner‐type peanut cultivar that was developed from a cross between 'C‐99R' and 'COAN'. Georgia Green is a normal‐oleic, TSWV‐resistant runner‐type cultivar that was developed from a cross between 'Southern Runner' and 'Sunbelt Runner'. Pedigree selection was practiced within the early segregating generations. Performance testing began in the F4:6 generation with the advanced pure‐line selection, GA 122544, the experimental designation of Georgia‐23RKN. During the past 3 years (2015–2017) and averaged over 29 multiple location tests without nematode pressure in Georgia, Georgia‐23RKN had significantly less TSWV and total disease incidence compared to Tifguard. Georgia‐23RKN was also found to have a larger runner seed size than the smaller runner‐type check cultivar, Georgia‐14N. Georgia‐23RKN combines high‐yield and TSWV‐ and RKN‐resistance with medium‐large seed size and the normal‐oleic trait preferred by large peanut butter manufacturers in the United States. Core Ideas: Georgia‐23RKN is a new runner‐type peanut cultivar.Georgia‐23RKN has very high root‐knot nematode resistance.Georgia‐23RKN has a normal‐oleic fatty acid ratio. [ABSTRACT FROM AUTHOR]

Phenotyping yam (Dioscorea spp.) germplasm for resistance to parasitic nematodes is hampered by the lack of an efficient screening method. In this study, we developed a new method using rooted yam vine cuttings and yam plantlets generated from semi-autotrophic hydroponics (SAHs) propagation for phenotyping yam genotypes for nematode resistance. The method was evaluated using 26 genotypes of D. rotundata for their reaction to Scutellonema bradys and four root-knot nematode species, Meloidogyne arenaria, M. enterolobii, M. incognita, and M. javanica. Yam plantlets established in nursery bags filled with steam-sterilized soil were used for screening against single nematode species. Plants were inoculated four weeks after planting and assessed for nematode damage eight weeks later. A severity rating scale was used to classify genotypes as resistant, tolerant, or susceptible determine based on the nematode feeding damage on tubers and the rate of nematode multiplication in the roots of inoculated plants. The results demonstrated putative resistance and tolerance against S. bradys in 58% of the genotypes and 88%, 65%, 65%, and 58% against M. arenaria, M. javanica, M. incognita, and M. enterolobii, respectively. The method is rapid, flexible, and seasonally independent, permitting year-round screening under controlled conditions. This method increases the throughput and speed of phenotyping and improves the selection process. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the plant defence-promoting ability of various nematophagous fungi like Arthrobotrys oligospora, Paecilomyces lilacinus and Pleurotus sp. against root-knot nematode Meloidogyne incognita in tomato by determining the plant defence-promoting biomolecules, viz. hydrogen peroxide, superoxide dismutase, catalase, peroxidase and polyphenol oxidase. It was observed that soil application of A. oligospora along with farmyard manure (FYM) enhanced the activity of defence-related biomolecules from day 30 to day 60 after transplant, thereby showing its immense potential in controlling root-knot nematodes in tomatoes. The highest mean defence-related enzyme activity in plants was recorded in the treatment containing nematode-infested soil + FYM + A. oligospora with 97.65 enzyme unit (EU) mg-1 protein min-1 of hydrogen peroxide, 1.54 EU mg-1 protein min-1 of superoxide dismutase, 4.57 EU mg-1 protein min-1 of catalase, 9.45 EU mg-1 protein min-1 of peroxidase and 5.89 EU mg-1 protein min-1 of polyphenol oxidase. The gall production in nematode-infested soil had also reduced drastically after the application of the nematophagous fungi. [ABSTRACT FROM AUTHOR]

The occurrence of root-knot nematode disease has seriously constrained the development of the Chinese herbal medicine industry. China is one of the largest producers of Polygonatum sibiricum and Peucedanum praeruptorum in the world, but the unidentified root-knot nematodes have become important pests of these two Chinese herbal medicines in China. Both morphological characteristics and molecular identification were used to identify the nematodes. The identification results showed that Meloidogyne incognita and M. arenaria were the causal species of root-knot nematode infection in P. sibiricum, and M. hapla was the causal species of the infection in P. praeruptorum. Through investigation, this is the first report of M. incognita and M. arenaria infecting P. sibiricum, and M. hapla infecting P. praeruptorum, in China. The two Chinese herbs are being severely damaged by various root-knot nematodes, and this damage should be taken seriously. [ABSTRACT FROM AUTHOR]

The biocontrol agent Pythium oligandrum, which is a member of the phylum Oomycota, can control diseases caused by a taxonomically wide range of plant pathogens, including fungi, bacteria, and oomycetes. However, whether P. oligandrum could control diseases caused by plant root-knot nematodes (RKNs) was unknown. We investigated a recently isolated P. oligandrum strain GAQ1, and the P. oligandrum strain CBS530.74, for the control of an RKN Meloidogyne incognita infection of tomato (Solanum lycopersicum L.). Initially, P. oligandrum culture filtrates were found to be lethal to M. incognita second-stage juveniles (J2s) with up to 84% mortality 24 h after treatment compared to 14% in the control group. Consistent with the lethality to M. incognita J2s, tomato roots treated with P. oligandrum culture filtrates reduced their attraction of nematodes, and the number of nematodes penetrating the roots was reduced by up to 78%. In a greenhouse pot trial, the P. oligandrum GAQ1 inoculation of tomato plants significantly reduced the gall number by 58% in plants infected with M. incognita. Notably, the P. oligandrum GAQ1 mycelial treatment significantly increased tomato plant height (by 36%), weight (by 27%), and root weight (by 48%). A transcriptome analysis of tomato seedling roots inoculated with the P. oligandrum GAQ1 strain identified ~2500 differentially expressed genes. The enriched GO terms and annotations in the up-regulated genes suggested a modulation of the plant hormone-signaling and defense-related pathways in response to P. oligandrum. In conclusion, our results support that P. oligandrum GAQ1 can serve as a potential biocontrol agent for M. incognita control in tomato. Multiple mechanisms appear to contribute to the biocontrol effect, including the direct inhibition of M. incognita, the potential priming of tomato plant defenses, and plant growth promotion. [ABSTRACT FROM AUTHOR]

Plant parasitic nematodes are harmful agricultural pests, causing severe yield losses of a wide range of crops worldwide. The lack of effective nematode management products has increased demand for innovative nematode management tools. This work was conducted to test propolis (bee glue) at different concentrations to control the root-knot nematode (Meloidogyne spp.) under laboratory conditions. A sample of propolis was measured and ethanol solvent (95%) was added and kept at room temperature for 24 h. The nematode eggs were exposed to the propolis extract at different concentrations (i.e., 2000, 4000, and 6000 ppm) for 24, 48, and 72 h. Results showed that propolis extract caused significant decreases in egg hatching, but to varying degrees. There was a gradual decrease in egg hatching with increasing the extract concentration and the duration of exposure. [ABSTRACT FROM AUTHOR]

Nowadays, plant extracts are extensively used as eco-friendly strategies for biological control of parasitic pests, including the root-knot nematodes, instead of using chemical pesticides. Therefore, the aim of this study was to examine leaf extract of neem plants (Azaddirachta indica) against the root-knot nematode; Meloidogyne spp. The obtained results showed that there was a gradual decrease in egg hatching with increasing the neem leaf extract concentrations and the duration of exposure. The neem extract is highly effective against egg hatching being the IC50 scored 397.1 ppm. Consequently, neem extract caused 75, 79, and 81% inhibition of egg hatching on root-knot nematode at the concentrations of 2000, 4000, and 6000 ppm, respectively at 72h. In contrast, the egg hatching (%) was progressively increased with increasing the exposure time from 24 to 72h. Under the application of plant extract concentrations for different periods, the lowest effective plant extract concentration was 2000 ppm, which gave the least inhibition, followed by 4000 ppm. The highest effective extract concentration was 6000 ppm, conferring the lowest egg hatching. It has been concluded from the results of the present study that the leaf extract of A. indica has the ability to inhibit the egg hatchability of root-knot nematode. Thus, this finding is important in the identification and development of alternative strategies in controlling the root-knot nematodes. There is, however, further work is needed to identify some of these main compounds after purification. This study confirms the presence of nematicidal compounds in petroleum ether fractions of Azadirachta indica, which were responsible for the prevention of egg hatching of root-knot nematodes at some concentrations, especially 6000 ppm. [ABSTRACT FROM AUTHOR]

In this study, the biological control effects of the Pseudomonas fluorescens strain CHA0 were compared to those of silicon (Si), used as a chemical control agent, against Meloidogyne javanica, the causative agent of root-knot disease in tomato plants. Indicators such as the number of M. javanica galls, eggs, egg masses, and the enzymatic activities of peroxidase (POX) and phenylalanine ammonia-lyase (PAL) were analysed. Results showed a significant reduction in the numbers of galls, eggs, and egg masses produced by M. javanica on tomato plants treated with P. fluorescens CHA0 (applied as a soil additive) as well as with Si (applied as a root and foliar treatment). The enzymatic activities peaked on the fifth day post-inoculation with M. javanica and then gradually declined. The greatest increase in enzymatic activities was observed in the combined treatment with M. javanica, P. fluorescens CHA0, and Si (the N+B+SiO2 treatment). The use of P. fluorescens CHA0 and Si enhanced the defence-related enzyme activity in tomato plants against M. javanica. However, high concentrations of Si were shown to inhibit the growth of P. fluorescens CHA0. [ABSTRACT FROM AUTHOR]

Root-knot nematodes (Meloidogyne spp.) are serious pests of most food crops, causing up to 100% yield loss. Nevertheless, commercial nematicides are costly and harmful to the environment. While the nematicidal potential of crustacean and synthetic chitin has been demonstrated globally, research on the potential of insect-derived chitin for nematode control has received limited attention. Here, seven chitin-fortified black soldier fly frass fertilizer extracts (chFE) were assessed for their suppressiveness of Meloidogyne incognita and impacts on spinach growth in comparison with a commercial nematicide using in vitro and in vivo bioassays. The performance of chFE and control treatments was assessed by determining their effects on nematode egg hatchability; infective juvenile (J2) mortality and paralysis; number of galls, egg masses, and J2s per plant; and spinach root and shoot biomass. In vitro results showed that chFE and commercial nematicide suppressed nematode egg hatchability by 42% and 52%, respectively, relative to the control (sterile distilled water). Up to 100% paralysis was achieved when M. incognita J2s were exposed to either chFE or commercial nematicide. Further, the J2 mortality achieved using chFE (95%) was comparable to the value achieved using commercial nematicide (96%); in all treatments, mortality increased with exposure time. Similarly, up to 85% suppression of gall development was achieved when spinach plants were grown in soil drenched with chFE; up to 79% reduction in egg mass formation and 68% suppression of J2 development in the root system were achieved using chFE. Also, chFE application significantly increased spinach root and shoot biomass by 54%-74% and 39%-58%, respectively, compared to commercial nematicide. Our findings demonstrate the nematicidal potential of chFE and its benefits on crop production. Thus, chFE could be considered as a promising multipurpose, regenerative, and cost-effective input for sustainable management of plantparasitic nematodes and enhancement of crop yield. [ABSTRACT FROM AUTHOR]

Root-knot nematode (Meloidogyne incognita) poses a significant threat to okra production, resulting in substantial yield losses. The objectives of this study were to assess the impact of biological seed protectants on the growth and establishment of okra plants and nematode population reduction in soil. Okra seeds were coated with 40% sesame oil, 50% neem oil, 100% citrus oil, velum at 3.8 ml/7l of water, and a control (sterilized distilled water) at different time intervals of 30 min, 60 min, 90 min, and 120 min to determine the germination percentages and vigor. The experimental setup was laid out in a completely randomized design (CRD), with three replications, utilizing a Jacobson table for the germination test. The laboratory results demonstrated significant differences (P < 0.05) in germination percentage and vigor index across the different time intervals. Neem oil, citrus oil, and velum exhibited higher germination percentages and vigor indices at all time intervals. Notably, 30-minute time interval proved to be efficient with 100% citrus oil producing 80.33% germination and 965 vigor index and 50% neem oil producing 75% germination and 994 vigor index. Field evaluations revealed citrus at 100% concentrations as seed coating (T5) and neem at 50% concentrations as seed coating (T3), with the highest nematode reductions (90.1% and 90.4%) and least reproductive factors (RFs) of 0.05 and 0.04, respectively, at the Atomic farms. The study has revealed that treating okra seeds with 100% citrus oil and 50% neem oil has the efficacy of reducing nematode reproduction in soil, while enhancing germination and seedling vigor, together with an improvement in growth and yield. Sesame oil has a negative influence on seed germination and vigor and is therefore not recommended as a preplant protectant. [ABSTRACT FROM AUTHOR]

The root-knot nematode (RKN) Meloidogyne spp. incurs substantial economic losses in vegetable crops. The present investigation involved glass-house-based screening performed by artificial inoculation of a set of 62 cauliflower accessions against RKN infestation. The PAUCE-292 genotype exhibited a resistant reaction to RKN infestation while genotypes PAUCE-15, PAUCE-16, PAUCE-19C and PAUCM-PI exhibited a moderately resistant reaction. Nematode inoculation reduced various growth parameters including plant height, plant weight and root length as compared to control but a higher percent reduction was recorded for the susceptible and highly susceptible genotypes. The root galling intensity was recorded to be high in susceptible and highly susceptible genotypes. The root-morphoanatomy studies on selected genotypes revealed no specific association of the studied traits with RKN reaction. But, optical microscopy revealed elaborate lignification and gall formation on RKN inoculation in susceptible PAUCM-SD3 and highly susceptible PAUCM-STAR accessions. The total phenol and flavonoid contents were maintained at significantly high levels in resistant genotype(s) in the initial 2.5-week post-inoculation of nematode juveniles. Therefore, this study provides biochemical cues on the mechanism of RKN resistance in cauliflower accessions. [ABSTRACT FROM AUTHOR]

Root-knot nematode host status of hemp cultivars of different uses (fiber, dual, CBD/CBG) and from different regions (Europe, China, US) were evaluated in five different greenhouse trials. None of the tested cultivars showed resistance to any of the tested root-knot nematode species, and all tested hemp cultivars were good hosts for root-knot nematodes, especially to mixed populations of M. javanica and M. incognita. Root gall symptoms on hemp were less severe than on cucumber (and tomato), but reproduction rates were similar. Lower infection and reproduction rates were noted for M. hapla and M. enterolobii, which were probably due to the colder temperatures at the time of the trial, as the same effect was noted for the cucumber control plants. While no negative impact on hemp shoot growth was seen in trials where nematodes were added to pasteurized soil, a significant and visible negative effect on hemp growth was noted when two CBG hemp cultivars were planted in heavily naturally root-knot infested soil. This result indicates that hemp is not only a good host to root-knot nematodes, but also that root-knot can be a limiting factor for hemp production in Florida and other places with high abundance and pressure of root-knot nematodes. [ABSTRACT FROM AUTHOR]

Root‐knot nematodes (Meloidogyne spp.) cause serious damage to kiwifruit orchards in Türkiye. In summer 2022, during a survey on root‐knot nematodes of kiwifruit in Bursa, Rize, and Yalova provinces in the country, many galls in the roots were discovered. A single egg mass was extracted from the infected roots and inoculated to Rutgers tomato and kiwi (Hayward) plants for reproduction as a pure culture. Second‐stage infective juveniles (J2), mature females with egg masses, and males were used for identification studies. Species were identified based on biochemical (esterase phenotypes), morphological, morphometric, and molecular methods. The perineal pattern observations and morphometric values were in accordance with previously reported measurements. The isozyme electrophoresis analyses revealed the species‐specific esterase phenotypes (E3) with three bands. As a result of all the methods used for diagnosis, we identified the nematode causing the infection as the root‐knot nematode Meloidogyne ethiopica. To our knowledge, this is not only the first report of M. ethiopica in Türkiye, but also the first report of this species in Europe. [ABSTRACT FROM AUTHOR]

Summary: The root-knot nematode, Meloidogyne enterolobii , is an important pathogen of numerous crops, including the so-called pulses. Hence, it is necessary to identify genetic resistance, as it is the most efficient, cost-effective, and environmentally sound way to manage nematodes in the field. The objective of this study was to screen a Brazilian germplasm collection of pulse crops (peas, chickpeas, and lentils) comprising accessions from the Embrapa Germplasm Bank and commercial cultivars against M. enterolobii under glasshouse conditions. The experiment was conducted with 23 treatments (genotypes), i.e., 14 pea, six chickpea and one lentil genotype, and two tomato cultivars, 'Rutgers' (susceptible) and 'Nemadoro' (resistant). Each plant (replication) was inoculated with 5000 eggs and second-stage juveniles (J2) of M. enterolobii and evaluated 65 days after inoculation, considering the following variables: gall index, egg mass index, number of eggs per g of roots, and reproduction factor. The experiments were conducted at two independent time points (summer and autumn/winter). Results showed that all 23 plant genotypes were susceptible to the nematode, with pea genotype 'Itapuã' being intolerant to infection. Cultivation of pulse crops has been steadily increasing both in Brazil and worldwide. Our research findings make a valuable contribution to the ongoing efforts to identify genetic resistance to nematode pathogens that can significantly affect the productivity of these crops. By identifying and developing resistant genotypes, pulse crop yields can be safeguarded, and sustainable agricultural practices can be supported. [ABSTRACT FROM AUTHOR]