Meloidogyne Graminicola Research Articles

Bioefficacy evaluation of chalcone derivatives against Meloidogyne graminicola infecting rice, Oryza sativa L.

A series of chalcones (1–14) were synthesized, characterized (using IR and 1H NMR techniques), and evaluated with an objective to manage rice root-knot nematode (RRKN) (Meloidogyne graminicola) both under pluronic gel and field conditions. Out of these fourteen compounds, 1-(4-fluoro-phenyl)-3-phenyl-propenone (13) and 1,3-diphenyl-propenone (14) showed promising and dose dependent activity at 10, 20, and 40 mg L−1. A significant reduction in penetration of second stage juveniles (J2s) in rice roots was observed in compounds 13 (9.5–12.0 J2s/plant) and 14 (10.5–13.4 J2s/plant) compared to control plants (PB1121) (13.5–23.6 J2s/plant) in pluronic gel study. The results of field trials indicated that 14, showed significantly (P ≤ 0.05) better plant growth on 28 days after sowing (DAS) compared to 13. Both 13 and 14 reduced gall formation significantly than carbofuran 3 G @1 kg a.i./ha. However, lower concentrations were less effective in field in reducing the gall formation. Also, a significant reduction in the number of galls was observed when soil was drenched with 14 @ 40 mg L−1. However, root dipping was not as effective as soil drenching. The study revealed that both the chalcones have the potential for effective management of RRKN in fields, and can be a better alternative to carbofuran.

Management of rice root-knot nematode (Meloidogyne graminicola Golden and Birchfield)–An integrated approach

An experiment was conducted to know the efficacy of bio agents viz., Purpureocillium lilacinum, Trichoderma harzianum, Bacillus subtilis,Bacillus megaterium, Vermicompost and Consortium of bio-agents (Purpureocillium lilacinum + Trichoderma harzianum + Bacillus subtilis +Bacillusmegaterium +Vermicompost) and Carbofuran3G @ 0.3 i.e., alone for management of rice root-knot nematode Meloidogyne graminicola for one season at Chikadadakatte village of Honnali taluk, Davanagere district during Kharif- 2018. The results revealed that all the treatments were significantly superior over check with respect to growthparameters and nematode population. However, carbofuran 3G significantly reduced the nematode population (275.11 /200 cc soil)which was found to be the best treatment as it recorded highest plant height (114.06 cm), root length (23.13 cm), maximum grain yield (44.60 q/ha) with least RKI (1.20) followed byConsortium of bio-agents (Purpureocilliumlilacinum + Trichoderma harzianum + Bacillus subtilis +Bacillusmegaterium +Vermicompost).

Rice Root-Knot Nematode Meloidogyne graminicola (Nematoda: Chromadorea: Tylenchida: Meloidogynidae: Meloidogyne)

The Featured Creatures collection provides in-depth profiles of insects, nematodes, arachnids and other organisms relevant to Florida. These profiles are intended for the use of interested laypersons with some knowledge of biology as well as academic audiences. Rice root-knot disease is caused by different Meloidogyne species (Meloidogyne graminicola, M. hainanensis, M. incognita, M. javanica, M. arenaria, M. oryzae, M. salasi, and M. tryticoryzae). However, Meloidogyne graminicola is considered the most damaging root-knot species to Asian rice cultivation due to its ability to survive under flooded soil conditions. This nematode has been found in rice nurseries, rainfed upland rice and lowland rice but is also widespread in deep-water, irrigated rice production systems. Yield loss due to Meloidogyne graminicola ranges from 28%–87% depending on disease severity and cultivar.

Seed treatments for control of Meloidogyne graminicola in flooded rice

Seed treatments for control of Meloidogyne graminicola in flooded rice

An improved draft genome assembly of Meloidogyne graminicola IARI strain using long-read sequencing.

The rice root-knot nematode Meloidogyne graminicola is a major biotic stress for the rice crop under upland, rain-fed lowland and irrigated cultivation conditions. Here, we present an improved draft genome assembly of M. graminicola IARI strain using the long-read sequencing approach (PacBio Sequel platform). The assembled genome size was 36.86Mb with 514 contigs and N50 value of 105kb. BUSCO estimated the genome to be 88.6% complete. Meloidogyne graminicola genome contained 17.83% repeat elements and showed 14,062 protein-coding gene models, 4,974 conserved orthologous genes, 561 putative secreted proteins, 49 RNAi pathway genes, 1,853 proteins involved in pathogen-host interactions, 1,575 carbohydrate-active enzymes, and 32,138 microsatellites. Five of the carbohydrate-active enzymes were found only in M. graminicola genome and were not present in any other analysed root-knot nematode genome. Together with the previous two genome assemblies, this improved genome assembly would facilitate comparative and functional genomics for M. graminicola.

The response of rice varieties to Meloidogyne graminicola from the Mekong Delta, Vietnam

Summary The rice root-knot nematode, Meloidogyne graminicola, is a serious pathogen of rice production worldwide. In Vietnam, scientific information on the rice root-knot nematode is limited. In this circumstance, our study aimed to investigate the characteristics of M. graminicola from rice fields in southern Vietnam and to evaluate the reaction of 20 rice varieties to this soil-borne pathogen in a glasshouse experiment. Ten populations of root-knot nematode collected from rice fields at different geographical regions in the Mekong Delta were identified as M. graminicola based on the perineal configuration of females and species-specific molecular markers. The morphological, morphometric and molecular characteristics of ten nematode isolates were defined, and the variations observed between these isolates were not significantly different. The pathogenicity of these isolates was examined in the susceptible Indica rice, Oryza sativa ‘IR64’, with a reproduction factor ranging from 18.1 to 37.8. Of the 20 Indica rice varieties tested in response to the nematode population MG-PN08, the ‘Tetep’ variety showed moderate resistance to the nematode (reproductive factor = 11.7; galling index = 2.4), while others were ranked at levels ranging from moderately susceptible to highly susceptible. The life cycle of M. graminicola in ‘Tetep’ root is 28 days compared to 21 in ‘IR64’. ‘Tetep’-nematode interaction at the histological and molecular levels needs further investigation to develop new rice varieties resistant to rice root-knot nematode.

The Meloidogyne graminicola effector MgMO289 targets a novel copper metallochaperone to suppress immunity in rice.

Recent studies have reported that plant-parasitic nematodes facilitate their infection by suppressing plant immunity via effectors, but the inhibitory mechanisms remain poorly understood. This study found that a novel effector MgMO289 is exclusively expressed in the dorsal esophageal gland of Meloidogyne graminicola and is up-regulated at parasitic third-/fourth-stage juveniles. In planta silencing of MgMO289 substantially increased plant resistance to M. graminicola. Moreover, we found that MgMO289 interacts with a new rice copper metallochaperone heavy metal-associated plant protein 04 (OsHPP04), and that rice cytosolic COPPER/ZINC -SUPEROXIDE DISMUTASE 2 (cCu/Zn-SOD2) is the target of OsHPP04. Rice plants overexpressing OsHPP04 or MgMO289 exhibited an increased susceptibility to M. graminicola and a higher Cu/Zn-SOD activity, but lower O2•- content, when compared with wild-type plants. Meanwhile, immune response assays showed that MgMO289 could suppress host innate immunity. These findings reveal a novel pathway for a plant pathogen effector that utilizes the host O2•--scavenging system to eliminate O2•- and suppress plant immunity.

Identification of multi-facial microbial isolates from the rice rhizosphere and their biocontrol activity against Rhizoctonia solani AG1-IA

Identification of multi-facial biocontrol agents that could act against different pathogens of rice crop shall be an interesting approach to develop effective strategies of biocontrol in practice. To identify the promising multi-facial microbial isolates (MIs) from the rice rhizosphere, twelve native MIs which had already been tested against rice root-knot nematode (Meloidogyne graminicola) were screened in vitro against sheath blight pathogen of rice, Rhizoctonia solani AG1-IA. The MIs exhibited substantial variability in their ability to inhibit the mycelial growth of R. solani. Out of twelve, six most promising MIs were tested against R. solani under pot trials on rice cv. PusaSugandh-5. We observed 30–52% loss in plant growth with R. solani. However, soil treated with MIs significantly attenuated the adverse effect of sheath blight pathogen. Among the MIs, Pseudomonas putida AMUPP-1 was found to be most effective and suppressed the disease severity by 69% leading to a 21–49% improvement in plant growth. Furthermore, we observed that Trichoderma harzianum AMUTH-1, P. fluorescens AMUPF-1 and other MIs had lesser effectiveness compared to P. putida AMUPP-1. Interestingly, P. putida AMUPP-1 was also found to detoxify oxalic acid and able to produce ammonia, hydrogen cyanide, indole acetic acid, siderophore, and solubilized phosphorus. Moreover, validation trials under naturally infested field verified the effectiveness of P. putida AMUPP-1 with 61% improvement in rice yield. In addition to these, we also observed the effect of P. putida AMUPP-1 better than fungicide, propiconazole. The present study has identified the multi-facial nature of P. putida AMUPP-1 which effectively suppressed different group of rice pathogens, R. solani (in the present study) and M. graminicola (in a previous study).

A rice root-knot nematode Meloidogyne graminicola-resistant mutant rice line shows early expression of plant-defence genes

Resistance to rice root-knot nematode Meloidogyne graminicola in a mutant rice line is suggested to be conferred by higher expression of several genes putatively involved in damage-associated molecular pattern recognition, secondary metabolite biosynthesis including phytoalexins, and defence-related genes. Meloidogyne graminicola has emerged as the most destructive plant-parasitic nematode disease of rice (Oryza sativa L.). Genetic resistance to M. graminicola is one of the most effective methods for its management. A M. graminicola-resistant O. sativa ssp. indica mutant line-9 was previously identified through a forward genetic screen (Hatzade et al. Biologia 74:1197-1217, 2019). In the present study, we used RNA-Sequencing to investigate the molecular mechanisms conferring nematode resistance to the mutant line-9 compared to the susceptible parent JBT 36/14 at 24h post-infection. A total of 674 transcripts were differentially expressed in line-9. Early regulation of genes putatively related to nematode damage-associated molecular pattern recognition (e.g., wall-associated receptor kinases), signalling [Nucleotide-binding, Leucine-Rich Repeat (NLRs)], pathogenesis-related (PR) genes (PR1, PR10a), defence-related genes (NB-ARC domain-containing genes), as well as a large number of genes involved in secondary metabolites including diterpenoid biosynthesis (CPS2, OsKSL4, OsKSL10, Oscyp71Z2, oryzalexin synthase, and momilactone A synthase) was observed in M. graminicola-resistant mutant line-9. It may be suggested that after the nematode juveniles penetrate the roots of line-9, early recognition of invading nematodes triggers plant immune responses mediated by phytoalexins, and other defence proteins such as PR proteins inhibit nematode growth and reproduction. Our study provides the first transcriptomic comparison of nematode-resistant and susceptible rice plants in the same genetic background and adds to the understanding of mechanisms underlying plant-nematode resistance in rice.

A Meloidogyne graminicola Pectate Lyase Is Involved in Virulence and Activation of Host Defense Responses.

Plant-parasitic nematodes secrete an array of cell-wall-degrading enzymes to overcome the physical barrier formed by the plant cell wall. Here, we describe a novel pectate lyase gene Mg-PEL1 from M. graminicola. Quantitative real-time PCR assay showed that the highest transcriptional expression level of Mg-PEL1 occurred in pre-parasitic second-stage juveniles, and it was still detected during the early parasitic stage. Using in situ hybridization, we showed that Mg-PEL1 was expressed exclusively within the subventral esophageal gland cells of M. graminicola. The yeast signal sequence trap system revealed that it possessed an N-terminal signal peptide with secretion function. Recombinant Mg-PEL1 exhibited hydrolytic activity toward polygalacturonic acid. Rice plants expressing RNA interference vectors targeting Mg-PEL1 showed an increased resistance to M. graminicola. In addition, using an Agrobacterium-mediated transient expression system and plant immune response assays, we demonstrated that the cell wall localization of Mg-PEL1 was required for the activation of plant defense responses, including programmed plant cell death, reactive oxygen species (ROS) accumulation and expression of defense-related genes. Taken together, our results indicated that Mg-PEL1 could enhance the pathogenicity of M. graminicola and induce plant immune responses during nematode invasion into plants or migration in plants. This provides a new insight into the function of pectate lyases in plants-nematodes interaction.

Plasmodesmata play pivotal role in sucrose supply to Meloidogyne graminicola-caused giant cells in rice.

On infection, plant‐parasitic nematodes establish feeding sites in roots from which they take up carbohydrates among other nutrients. Knowledge on how carbohydrates are supplied to the nematodes’ feeding sites is limited. Here, gene expression analyses showed that RNA levels of OsSWEET11 to OsSWEET15 were extremely low in both Meloidogyne graminicola (Mg)‐caused galls and noninoculated roots. All the rice sucrose transporter genes, OsSUT1 to OsSUT5, were either down‐regulated in Mg‐caused galls compared with noninoculated rice roots or had very low transcript abundance. OsSUT1 was the only gene up‐regulated in galls, at 14 days postinoculation (dpi), after being highly down‐regulated at 3 and 7 dpi. OsSUT4 was down‐regulated at 3 dpi. No noticeable OsSUTs promoter activities were detected in Mg‐caused galls of pOsSUT1 to ‐5::GUS rice lines. Loading experiments with carboxyfluorescein diacetate (CFDA) demonstrated that symplastic connections exist between phloem and Mg‐caused giant cells (GCs). According to data from OsGNS5‐ and OsGSL2‐overexpressing rice plants that had decreased and increased callose deposition, respectively, callose negatively affected Mg parasitism and sucrose supply to Mg‐caused GCs. Our results suggest that plasmodesmata‐mediated sucrose transport plays a pivotal role in sucrose supply from rice root phloem to Mg‐caused GCs, and OsSWEET11 to ‐15 and OsSUTs are not major players in it, although further functional analysis is needed for OsSUT1 and OsSUT4.

Genome‐wide shifts in histone modifications at early stage of rice infection with Meloidogyne graminicola

Epigenetic processes play a crucial role in the regulation of plant stress responses, but their role in plant–pathogen interactions remains poorly understood. Although histone‐modifying enzymes have been observed to be deregulated in galls induced by root‐knot nematodes (RKN, Meloidogyne graminicola) in rice, their influence on plant defence and their genome‐wide impact has not been comprehensively investigated. First, the role of histone modifications in plant–nematode interactions was confirmed by pharmacological inhibition of histone‐modifying enzymes, which all significantly affected rice susceptibility to RKN. For a more specific view, three histone marks, H3K9ac, H3K9me2, and H3K27me3, were subsequently studied by chromatin‐immunoprecipitation‐sequencing on RKN‐induced galls at 3 days postinoculation. While levels of H3K9ac and H3K27me3 were strongly enriched, H3K9me2 was generally depleted in galls versus control root tips. Differential histone peaks were generally associated with plant defence‐related genes. Transcriptome analysis using RNA‐Seq and RT‐qPCR‐based validation revealed that genes marked with H3K9ac or H3K9me2 showed the expected activation or repression gene expression pattern, but this was not the case for H3K27me3 marks. Our results indicate that histone modifications respond dynamically to RKN infection, and that posttranslational modifications mainly at H3K9 specifically target plant defence‐related genes.

Potensi Beberapa Isolat Bakteri Endofit untuk Pengendalian Biologi Meloidogyne graminicola pada Tanaman Padi

Meloidogyne graminicola merupakan salah satu nematoda parasit penting pada tanaman padi. M. graminicola menyebabkan gejala puru pada akar sehingga pertumbuhan tanaman terhambat dan terganggu. Pengendalian M. graminicola sangat penting dilakukan agar kerusakan pada tanaman padi dan penyebarannya dapat ditekan. Penelitian ini bertujuan untuk menguji potensi bakteri endofit dalam mengendalikan nematoda puru akar (NPA) M. graminicola pada tanaman padi. Empat isolat bakteri endofit asal tanaman padi, yaitu isolat Si33, Si2, Sp24, GH1, dan satu isolat asal tanaman kentang G053 diuji untuk melihat pengaruhnya terhadap mortalitas M. gramincola secara in vitro dan kemampuannya dalam menekan serangan M. graminicola pada tanaman padi di rumah kaca. Hasil uji kultur filtrat bakteri endofit secara in vitro terbukti efektif meningkatkan kematian juvenil 2 M. graminicola sebesar 99.5% hingga 100%. Isolat bakteri endofit juga mampu menekan jumlah puru akar pada tanaman padi dengan kisaran 42.2%–49.3% pada percobaan di rumah kaca. Hasil penelitian ini mengindikasikan bahwa isolat bakteri endofit yang digunakan dalam penelitian ini mempunyai potensi yang baik sebagai agens biokontrol untuk mengendalikan M. graminicola pada tanaman padi.

Application of biochar and vermicompost against the rice root-knot nematode (Meloidogyne graminicola): an eco-friendly approach in nematode management

The rice root-knot nematode (Meloidogyne graminicola) is one of the key pests of rice (Oryza sativa L.) in irrigated and upland rice ecosystems inflicting about 20–80% yield loss. While chemical nematicides are widely used to combat this pest, they have a negative impact on the environment as well as on animal and human health. The present study evaluated the efficacy of organic amendments like biochar and vermicompost in managing the rice root-knot nematode (RRKN) at 0.6, 1.2, 2.5, and 5% (w/v) concentrations. Our result showed that biochar and vermicompost exudate neither exhibit any direct killing ability nor altered the infectivity of RRKN second-stage juveniles (J2). Second-stage juvenile hatching was, however, reduced in two higher doses (2.5% and 5%) of vermicompost exudates. When final nematode population was normalized with root weights at 21 days’ post inoculation, a reduction in population build-up was observed with increased doses of vermicompost. A reverse trend was observed for biochar treatments. Overall, our study showed that application of 1.2% biochar and 5% vermicompost could be helpful in mitigating the RRKN stress in rice. Hence, application of biochar and vermicompost could be an effective alternative to toxic chemical nematicides and recommended as eco-friendly management options against M. graminicola in rice.

Control of Meloidogyne graminicola a Root-Knot Nematode Using Rice Plants as Trap Crops: Preliminary Results

Meloidogyne graminicola is one of the most harmful organisms in rice cultivation throughout the world. This pest was detected for the first time in mainland Europe (Northern Italy) in 2016 and was subsequently added to the EPPO Alert List. To date, few methods are available for the control of M. graminicola and new solutions are required. In 2019, field trials using rice plants as trap crops were performed in a Lombardy region rice field where five plots for three different management approaches were staked out: (i) Uncultivated; (ii) Treated: three separate cycles of rice production where plants were sown and destroyed each time at the second leaf stage; (iii) Control: rice was sown and left to grow until the end of the three cycles in treated plots. The results showed that in the treated plots, the nematode density and the root gall index were lower than for the other two management approaches. Moreover, the plant population density and rice plant growth were higher than the uncultivated and control plots. In conclusion, the use of the trap crop technique for the control of M. graminicola gave good results and thus it could be a new phytosanitary measure to control this pest in rice crop areas.

Efficacy of Essential Oils and Their Major Compounds against Meloidogyne graminicola (Rice Root-Knot Nematode) in Pots and Field Trials

Efficacy of Essential Oils and Their Major Compounds against Meloidogyne graminicola (Rice Root-Knot Nematode) in Pots and Field Trials

First report of rice root-knot nematode, Meloidogyne graminicola, infecting Juncus microcephalus in Brazil.

Juncus microcephalus plants showing symptoms of root-knot nematode infestation were observed in the municipality of Agudo, Rio Grande do Sul state, Brazil. Based on morphological observation, esterase phenotypes, and molecular analyses of rDNA-ITS and D2-D3 regions of 28S rDNA, the causal agent of the observed symptoms was identified as Meloidogyne graminicola. Pathogenicity of M. graminicola was confirmed by fulfilling modified Koch’s postulates. To our knowledge, this is the first report of M. graminicola in J. microcephalus in Rio Grande do Sul State, Brazil.

Influence of Summer Green Manuring on Soil Nematode Population under Rice-Wheat Cropping System

Experiments were conducted to study effect of incorporation summer green manuring on nematode population and plant growth of rice infested with rice root-knot nematode, Meloidogyne graminicola. Plant parts viz., shoot and roots of Crotalaria were used to incorporate into the soil. Total nematode population and plant growth parameters (shoot and root length, shoot and root weight) were recorded at 60 day after inoculation (DAI). In general, all the treatments increased the plant growth parameters significantly compared to control plants. Maximum increase in plant growth parameters was observed in treatment, where leaf and roots of C. juncea were incorporated simultaneously during transplanting of rice seedlings. The number of galls formed on rice roots was reduced in all the treatments compared to control (34.25), with maximum reduction (85.2%) in treated plants. Available nitrogen, phosphorus and potassium, organic carbon and % organic matter content of soil in pots of third treatment was significantly higher where Crotalaria were grown for 45 days and both leaves and roots of same plants incorporated into soil. Thus, the same treatment was studied under field conditions, along with mungbean as green manure crop and fallow as a recommended practice for nematode control. In this it was clear that Crotalaria was very effective compared to mungbean as well as fallow. The cultivation of C. juncea as a green manure crop for direct seeding or intercrops, or as organic soil amendment, can reduce or even eliminate plant parasitic nematodes, rice root-knot nematode.

High Throughput Screening of Introgression Lines of Rice for Resistance against Rice Root-Knot Nematode (Meloidogyne graminicola Golden & Birchfield)

High Throughput Screening of Introgression Lines of Rice for Resistance against Rice Root-Knot Nematode (Meloidogyne graminicola Golden & Birchfield)

Identification and Characterization of a Novel Protein Disulfide Isomerase Gene (MgPDI2) from Meloidogyne graminicola.

Protein disulfide isomerase (PDI) is a multifunctional enzyme that catalyzes rate-limiting reactions such as disulfide bond formation, isomerization, and reduction. There is some evidence that indicates that PDI is also involved in host-pathogen interactions in plants. In this study, we show that the rice root-knot nematode, Meloidogyne graminicola, has evolved a secreted effector, MgPDI2, which is expressed in the subventral esophageal glands and up-regulated during the early parasitic stage of M. graminicola. Purified recombinant MgPDI2 functions as an insulin disulfide reductase and protects plasmid DNA from nicking. As an effector, MgPDI2 contributes to nematode parasitism. Silencing of MgPDI2 by RNA interference in the pre-parasitic second-stage juveniles (J2s) reduced M. graminicola multiplication and also increased M. graminicola mortality under H2O2 stress. In addition, an Agrobacterium-mediated transient expression assay found that MgPDI2 caused noticeable cell death in Nicotiana benthamiana. An intact C-terminal region containing the first catalytic domain (a) with an active motif (Cys-Gly-His-Cys, CGHC) and the two non-active domains (b and b′) is required for cell death induction in N. benthamiana. This research may provide a promising target for the development of new strategies to combat M. graminicola infections.