Meloidogyne Javanica Research Articles

Application of rock dust for the management of Meloidogyne javanica in soybean

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.

Exploiting fly ash as an ecofriendly pesticide/nematicide on Abesmoschus esculuntus: Insights into soil amendment-induced antioxidant fight against nematode mediated ROS

Conventional pest control measures, such as chemical pesticides and nematicides, have limited efficacy and raise environmental concerns, necessitating sustainable and eco-friendly alternatives for pest management. Therefore, to find a complementary eco-friendly pesticide/nematicide, this study investigated the role of fly ash (FA) in managing a notorious pest, Meloidogyne javanica and its impact on the growth and physiology of Abelmoschus esculentus. Molecular characterization using SSU and LSU rDNA gene markers confirmed the identity of Indian M. javanica as belonging to the same species. Biotic stress induced by nematode infection was significantly alleviated (P < 0.05) by FA application at a 20% w/v, regulating of ROS accumulation (44.1% reduction in superoxide anions and 39.7% reduction in hydrogen peroxide content) in the host plant. Moreover, FA enhanced antioxidant defence enzymes like superoxide dismutase (46.6%) and catalase (112%) to combat nematode induced ROS. Furthermore, the application of FA at a 20% concentration significantly improved the biomass and biochemical attributes of okra. Fly ash also upregulated the activity of the important osmo-protectant proline (11.5 μmol/g FW) to mitigate nematode stress in host cells. Suppression of disease indices like gall index and reproduction factor, combined with in-vitro experiments, revealed that FA exhibits strong nematode mortality capacity and thus can be used as a sustainable and eco-friendly control agent against root-knot nematodes.

Parasitic Nematodes of Sugarcane: A Major Productivity Impediment and Grand Challenges in Management.

Sugarcane is an important cash crop grown in 137 countries, accounting for 80% of global sugar production. It supports the livelihood of more than 100 million people and up to 25% of the rural population in some countries. Plant-parasitic nematodes are one significant constraint in sugarcane production and can lead to a loss of up to 30% in productivity. More than 300 species of parasitic nematodes have been discovered in sugarcane soil. Owing to limited data, the potential damage to sugarcane crops caused by parasitic nematodes is often underestimated. The main nematodes present in sugarcane fields are root-lesion (Pratylenchus spp.), spiral (Helicotylenchus spp.), root-knot (Meloidogyne spp.), dagger (Xiphinema spp.), stunt (Tylenchorhynchus spp.), ring (Criconemella spp.), and stubby (Paratrichodorus spp.). Among these, Meloidogyne javanica and Pratylenchus zeae are the most damaging nematode species. Management of nematodes is a challenging task as there are no clear symptoms of their presence, and they often come in multiple species with varying levels of pathogenicity. Moreover, the management options available are not always effective. Integrated nematode management is a sustainable strategy for controlling nematode infestations. It involves using all possible methods to suppress the parasitic nematode population in a compatible manner and reduce it below economic threshold levels. This article focuses on the challenges of managing nematodes in sugarcane and highlights the opportunity for implementing a sustainable nematode management strategy.

Comparative analysis of antioxidant enzyme activity and defence responses in root‐knot nematode resistant and susceptible carrot cultivars

AbstractRoot‐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.

The other side of the coin: systemic effects of Serendipita indica root colonization on development of sedentary plant–parasitic nematodes in Arabidopsis thaliana

Main conclusionUpon systemic S. indica colonization in split-root system cyst and root-knot nematodes benefit from endophyte-triggered carbon allocation and altered defense responses what significantly facilitates their development in A. thaliana.Serendipita indica is an endophytic fungus that establishes mutualistic relationships with different plants including Arabidopsis thaliana. It enhances host’s growth and resistance to different abiotic and biotic stresses such as infestation by the cyst nematode Heterodera schachtii (CN). In this work, we show that S. indica also triggers similar direct reduction in development of the root-knot nematode Meloidogyne javanica (RKN) in A. thaliana. Further, to mimick the natural situation occurring frequently in soil where roots are unequally colonized by endophytes we used an in vitro split-root system with one half of A. thaliana root inoculated with S. indica and the other half infected with CN or RKN, respectively. Interestingly, in contrast to direct effects, systemic effects led to an increase in number of both nematodes. To elucidate this phenomenon, we focused on sugar metabolism and defense responses in systemic non-colonized roots of plants colonized by S. indica. We analyzed the expression of several SUSs and INVs as well as defense-related genes and measured sugar pools. The results show a significant downregulation of PDF1.2 as well as slightly increased sucrose levels in the non-colonized half of the root in three-chamber dish. Thus, we speculate that, in contrast to direct effects, both nematode species benefit from endophyte-triggered carbon allocation and altered defense responses in the systemic part of the root, which promotes their development. With this work, we highlight the complexity of this multilayered tripartite relationship and deliver new insights into sugar metabolism and plant defense responses during S. indica–nematode–plant interaction.

Control of Meloidogyne javanica in banana by endophytic bacteria

Abstract The aim of this work was to evaluate the effect of 40 endophytic bacteria isolates on the control of Meloidogyne javanica in ‘Prata-Anã’ banana seedlings. Two experiments were carried out in a completely randomized design with eight replicates. In each trial, 20 bacteria isolates and control were evaluated. Bacterial suspensions were applied to substrates during the acclimatization of seedlings at 15 and 30 days. On the 31st day, seedlings were transplanted into pots and soil was infested with M. javanica egg suspension at 8 days. After 90 days, the following variables were evaluated: number of galls, egg masses, eggs per root, reproduction factor (RF), second-stage juveniles, and shoot dry matter. The results of nematological variables were submitted to Principal Components Analysis. In trial I, the variables that most contributed to data variability were as follows: number of eggs and RF. In trial II, RF had greater influence. Of the 40 isolates evaluated, 39 reduced RF, and of the 20 isolates evaluated in the first trial, all reduced the number of eggs per root. Bacillus methylotrophicus EB26, Bacillus cereus EB25, and Bacillus sp. EB37 isolates stood out in the control of nematodes, with RF reduction above 80%.

Diversity of plant-parasitic nematodes associated with chickpea (Cicer arietinum L.) in the main growing areas of Ethiopia

Summary Chickpea is one of the most important legume crops in Ethiopia; however, its production is far below the mean international chickpea production due to biotic and abiotic stressors. Plant-parasitic nematode infestation is extensive in chickpea-growing areas worldwide. The distribution and population density of plant-parasitic nematodes in chickpea were determined during the September-December 2021 growing season. Ten plant-parasitic nematode taxa were identified from 27 localities across ten districts in the main chickpea-growing areas in Ethiopia. Pratylenchus had the highest prominence values, followed by Rotylenchulus and Meloidogyne spp. Helicotylenchus, Hoplolaimus, Scutellonema and Quinisulcius were more prevalent than Criconemoides and Ditylenchus. Sequences of different molecular markers, including D2-D3 of 28S rDNA, ITS of rDNA, and COI and Nad5 of mtDNA, revealed the presence of Meloidogyne javanica, Rotylenchulus parvus, Scutellonema clathricaudatum and Helicotylenchus caudatus. Helicotylenchus caudatus and R. parvus are the first reports from Ethiopia and chickpea, while S. clathricaudatum is the first report for chickpea. This study provides essential baseline information of nematode pest occurrence on chickpea in Ethiopia. This information will raise awareness among growers, agricultural officers, and extension advisors, enabling them to develop effective nematode management strategies for the chickpea production system in Ethiopia.

Host-status of sixteen crops used in potato-based crop rotation systems against Meloidogyne javanica in South Africa

Root-knot nematodes (Meloidogyne species) are the most important group of plant nematodes in potato-producing regions of South Africa. Prior to the withdrawal of synthetic chemical fumigant nematicides from the agrochemical markets, Meloidogyne species were viewed as a minor pest in potato-producing regions. Currently, it has been established that all potato cultivars are host to Meloidogyne species, with the preferred management option of the genus being the use of resistant crops. However, the host status of most crops used in potato-based crop rotations intended to manage nematode population densities of the genus had not been established. Globally, M. incognita is viewed as being more aggressive than M. javanica, whereas in South Africa the opposite is true. Therefore, the objective of the study was to determine whether the reproduction potential (RP) values of M. javanica on 16 crops used in potato crop rotation systems would be below unity. The experiment was conducted under greenhouse conditions at the University of Limpopo during autumn (February-April) 2022 and validated in spring (September-November) of the same year in South Africa. Treatments (16 crops) were laid out in a randomized complete block design, with six replications. The crops were inoculated with 250 eggs + second-stage juveniles (J2). At 56 days after inoculation, nematodes variables were collected and expressed as RP, which demonstrated that there were similarities and differences in RP of the 16 crops to infection by M. javanica, but with the values being below one in white maluti oats, tillage radish, forage sorghum, and jap radish. In conclusion, the four crops with RP values below one could be used in a potato-crop rotation system intended to manage the population densities of M. javanica.

Potential of different species of actinobacteria in the management of Meloidogyne javanica.

Root-knot nematodes (RKN) are one of the most harmful soil-borne plant pathogens in the world. Actinobacteria are known phytopathogen control agents. The aim of this study was to select soil actinobacteria with control potential against the RKN (Meloidogyne javanica) in tomato plants and to determine mechanisms of action. Ten isolates were tested and a significant reduction was observed in the number of M. javanica eggs, and galls 46days after infestation with the nematode. The results could be explained by the combination of different mechanisms including parasitism and induction of plant defense response. The M. javanica eggs were parasited by all isolates tested. Some isolates reduced the penetration of juveniles into the roots. Other isolates using the split-root method were able to induce systemic defenses in tomato plants. The 4L isolate was selected for analysis of the expression of the plant defense genes TomLoxA, ACCO, PR1, and RBOH1. In plants treated with 4L isolate and M. javanica, there was a significant increase in the number of TomLoxA and ACCO gene transcripts. In plants treated only with M. javanica, only the expression of the RBOH1 and PR1 genes was induced in the first hours after infection. The isolates were identified using 16S rRNA gene sequencing as Streptomyces sp. (1A, 3F, 4L, 6O, 8S, 9T, and 10U), Kribbella sp. (5N), Kitasatospora sp. (2AE), and Lentzea sp. (7P). The efficacy of isolates from the Kitasatospora, Kribbella, and Lentzea genera was reported for the first time, and the efficacy of Streptomyces genus isolates for controlling M. javanica was confirmed. All the isolates tested in this study were efficient against RKN. This study provides the opportunity to investigate bacterial genera that have not yet been explored in the control of M. javanica in tomatoes and other crops.

Reaction of Stylosanthes spp. ‘Campo Grande’ to Pratylenchus brachyurus and Meloidogyne javanica and analysis of the histopathology and histochemistry of their interactions

Reaction of Stylosanthes spp. ‘Campo Grande’ to Pratylenchus brachyurus and Meloidogyne javanica and analysis of the histopathology and histochemistry of their interactions

Transcriptome Analysis of Meloidogyne javanica and the Role of a C-Type Lectin in Parasitism.

Meloidogyne javanica is one of the most widespread and economically important sedentary endoparasites. In this study, a comparative transcriptome analysis of M. javanica between pre-parasitic second-stage juveniles (Pre-J2) and parasitic juveniles (Par-J3/J4) was conducted. A total of 48,698 unigenes were obtained, of which 18,826 genes showed significant differences in expression (p < 0.05). In the differentially expressed genes (DEGs) from transcriptome data at Par-J3/J4 and Pre-J2, a large number of unigenes were annotated to the C-type lectin (CTL, Mg01965), the cathepsin L-like protease (Mi-cpl-1), the venom allergen-like protein (Mi-mps-1), Map-1 and the cellulase (endo-β-1,4-glucanase). Among seven types of lectins found in the DEGs, there were 10 CTLs. The regulatory roles of Mj-CTL-1, Mj-CTL-2 and Mj-CTL-3 in plant immune responses involved in the parasitism of M. javanica were investigated. The results revealed that Mj-CTL-2 could suppress programmed cell death (PCD) triggered by Gpa2/RBP-1 and inhibit the flg22-stimulated ROS burst. In situ hybridization and developmental expression analyses showed that Mj-CTL-2 was specifically expressed in the subventral gland of M. javanica, and its expression was up-regulated at Pre-J2 of the nematode. In addition, in planta silencing of Mj-CTL-2 substantially increased the plant resistance to M. javanica. Moreover, yeast co-transformation and bimolecular fluorescence complementation assay showed that Mj-CTL-2 specifically interacted with the Solanum lycopersicum catalase, SlCAT2. It was demonstrated that M. javanica could suppress the innate immunity of plants through the peroxide system, thereby promoting parasitism.

Metabolites from Lysobacter gummosus YMF3.00690 Against Meloidogyne javanica.

The strains in Lysobacter spp. have the potential to control plant-parasitic nematodes. In our experiment, L. gummosus YMF3.00690 showed antagonistic effects against plant root-knot nematode. Nine metabolites were isolated and identified from cultures of L. gummosus YMF3.00690, of which compound 1 was identified as a new metabolite tetrahydro-4,4,6-trimethyl-6-[(tetrahydro-6,6-dimethyl-2-oxo-4(1H)-pyrimidinylidene) methyl]-2(1H)-pyrimidinone. The activity assay showed that two compounds, 5-(hydroxymethyl)-1H-pyrrole-2-carbaldehyde (2) and 1H-pyrrole-2-carboxylic acid (3), had nematicidal activities against Meloidogyne javanica with mortalities of 69.93 and 90.54% at 400 ppm for 96 h, respectively. These two compounds were further tested for the inhibition activity of eggs hatching, and compound 3 showed a significant inhibition rate of 63.36% at 50 ppm for 48 h. In the chemotactic activity assay, three compounds (1 to 3) were found to have concentration-dependent chemotactic activity, of which compound 1 showed attractive activity. This experiment explored the active metabolites of L. gummosus YMF3.00690 against M. javanica and laid the foundation for biopesticide development.

Drivers of plant parasitic nematode community structures associated with tobacco‐growing areas in southern Brazil

AbstractTobacco (Nicotiana tabacum L.) is one of the most important crops in southern Brazil, but little is known about the distribution and diversity of plant parasitic nematodes (PPNs). We surveyed the occurrence and diversity of PPNs in 36 tobacco‐growing areas in southern Brazil as well as evaluated their relationship with 19 bioclimatic variables. For these purposes, extracted nematodes (from soil and roots) were identified based on morphological and biochemical traits and estimates of incidence and abundance were obtained, which were used to compute diversity indices. Furthermore, the relationship between taxa and diversity and the influence of bioclimatic variables were studied using principal component analysis (PCA) and generalized linear models (GLMs), respectively. We observed diversity across the sampled sites, with values varying from 0.03 to 1.22 and from 0.05 to 0.76 according to the Shannon‐Wiener and Pielou's evenness indices, respectively. Seven genera of PPNs (Meloidogyne, Helicotylenchus, Tylenchus, Xiphinema, Pratylenchus, Paratylenchus and Mesocriconema) were identified, highlighting taxa with high incidence and abundance, such as Meloidogyne (100%; 1800 to 41,850 specimens/250 cm3), Helicotylenchus (100%; 50 to 9850 specimens/250 cm3), and Pratylenchus (86.1%; 50 to 1950 specimens/250 cm3). The PCA disclosed the major roles of Meloidogyne, Tylenchus, and Helicotylenchus in the structure of the PPN communities and their interplays. Among root‐knot nematodes, Meloidogyne javanica, M. arenaria and M. incognita were the predominant species. Using GLMs, we found that average annual temperature and annual precipitation strongly influenced the abundance of PPNs as well as the diversity indices (p &lt; .01), with negative and/or positive interactions. Collectively, our findings fill gaps in knowledge about the current impact of PPNs and provide insights into future scenarios, including for other host crops.

Plant parasitic nematodes on soybean (Glycine max (L) Merr.) in the Metekel zone (Ethiopia) and varietal resistance evaluation to Meloidogyne javanica

AbstractPlant parasitic nematodes cause severe damage to soybean crops, leading to substantial losses in yield and quality. However, more information is needed regarding the occurrence, distribution and damage status of soybean PPNs in Ethiopia. A total of 180 samples of rhizosphere and roots were collected randomly from three major soybean‐producing districts of Metekel Zone. Nematodes were extracted and identified at the genus level based on their morphological characteristics, except Meloidogyne javanica, the deadly species, which was identified using morphological and molecular techniques. Seven nematode genera were recovered: Meloidogyne, Scutellonema, Pratylenchus, Helicotylenchus, Rotylenchulus, Hemicycliophora and Criconema. The genera Meloidogyne, Scutellonema and Pratylenchus were dominant and had FO% of 98.3%, 97.5% and 81.8%, respectively. The host status of 10 soybean varieties to M. javanica infection was determined. Data on the shoot height, root length, fresh shoot and root weight, gall number and nematode density were estimated 3 months after inoculation. The results revealed that Jalele variety suppresses M. javanica multiplication while the other nine supported it. Comparatively, Pawe‐3, Awassa‐95 and Koreme varieties supported the highest nematode multiplication 24.4, 16.2 and 15.3 reproductive factors, respectively. Nova experienced the highest shoot and root relative biomass losses (84%) and roots (63%). In contrast, Jalele did not experience any loss in all parameters. However, Jalele variety resisted M. javanica, making it a promising approach towards soybean breeding programs for nematode management.

Chemical control associated with genetic management of Meloidogyne javanica in soybean

Chemical control associated with genetic management of Meloidogyne javanica in soybean

Volatile organic compounds of the soil bacterium Bacillus halotolerans suppress pathogens and elicit defense-responsive genes in plants

Volatile organic compounds (VOCs) produced by bacteria play an important, yet relatively unexplored role in interactions between plants and phytopathogens. In this study, the soil bacterium Bacillus halotolerans NYG5 was identified as a potent biocontrol agent against several phytopathogenic fungi (Macrophomina phaseolina, Rhizoctonia solani, Pythium aphanidermatum, and Sclerotinia sclerotiorum) through the production of VOCs. NYG5-emitted VOCs also inhibited the growth of bacterial pathogens (Agrobacterium tumefaciens, Xanthomonas campestris, Clavibacter michiganensis, and Pseudomonas syringae). When cultured in various growth media, NYG5 produced a variety of VOCs. Five distinct VOCs (2-methylbutanoic acid, 5-methyl-2-hexanone, 2,3-hexanedione, 2-ethyl-1-hexanol, and 6-methyl-2-heptanone) were identified using headspace GC-MS. 2,3-Hexanedione exhibited potent lethal effects on the tested phytopathogens and nematicidal activity against Meloidogyne javanica at a concentration of 50 ppm. In addition, 0.05 ppm 2,3-hexanedione stimulated the expression of pathogenesis-related genes 1 and 2 in Arabidopsis thaliana. Interestingly, 2,3-hexanedione is used as a food additive at higher concentrations than those tested in this study. Hence, 2,3-hexanedione is a promising biologically active compound that might serve as a sustainable alternative to common chemical pesticides and an elicitor of plant defense.

Effect of Mulching Manures and Use of Heterorhabditis Bacteriophora on Strawberry Fruit Yield Temnorhynchus baal and Meloidogyne javanica Under Field Conditions

Abd-Elgawad, M.M.M., L.W. Duncan, M.M.A. Hammam, F. El-Borai and I.E. Shehata. 2024. Effect of Mulching Manures and Use of Heterorhabditis Bacteriophora on Strawberry Fruit Yield Temnorhynchus baal and Meloidogyne javanica Under Field Conditions. Arab Journal of Plant Protection, 42(3): 306-317. https://doi.org/10.22268/AJPP-001262 The importance of safe methods to manage strawberry pests has become more evident with increasing strawberry production and export in Egypt. Root damage by white grubs (Temnorhynchus baal larvae) and root-knot nematode (RKN), Meloidogyne javanica cause severe losses to strawberry fruit yield. Growers often rely on a few selective chemical pesticides to control these pests and to minimize pesticide residues in order to comply with maximum residue limits allowed for fruit export. Entomopathogenic nematodes (EPNs) that invade and kill grubs and reduce RKN population levels in the soil may be as effective as these insecticides in some cases. We evaluated the profitability of mulching strawberry with commonly used cow and/or chicken manure, with and without application of commercial Heterorhabditis bacteriophora in two farms for four consecutive years. All plots received chemical fertilizers. The designed drip irrigation system for EPN delivery in the farms insured efficient and even (P &lt; 0.05) application of EPN in all treatments. Timing of EPN application varied due to import regulatory guidelines. All manure mulch treatments increased strawberry yield each year at a farm in Al-Qalyubia governorate, whereas yield remarkably increased in the fourth season at the farm in El-Beheira governorate. Compared to EPN-treated plots, 70% more (P = 0.06) insects were recovered in soil beneath dead plants in plots that did not receive EPNs. Heterorhabditis bacteriophora boosted fruit yield (P &lt; 0.05) in the second and fourth years at El-Beheira and in all years at Al-Qalyubia. It reduced (P &lt; 0.05) numbers of Meloidogyne javanica galls/egg masses on strawberry roots and juveniles in the soil in both farms. Mulches had no measurable effect on EPN performance, but suppressed pests and boosted plant productivity. The greatest yield enhancement by EPN occurred in the second year at El-Beheira farm when EPNs were applied shortly after planting (October), enabling early season control of the pests, but in the third year at Al-Qalyubia farm where the weather was generally warmer than that at El-Beheira, and therefore more suitable for EPN activity. Keywords: Strawberry yield, entomopathogenic nematodes, Meloidogyne, mulching, Egypt.

Transcriptome-based analysis of candidate gene markers associated with resistance mechanism to Phytophthora melonis that causes root and crown rot in pumpkin.

Root and crown rot incited by an oomycete, Phytophthora melonis, causes significant yield losses in commercial pumpkin (Cucurbita pepo) production worldwide. Currently, resistant cultivars and knowledge of molecular mechanism of C. pepo against P. melonis are scarce. Here, we analysed the quantitative gene expression changes of 10 candidate gene markers (bHLH87, ERF014, HSF, MYB, PR-1, WRKY21, CPI, POD, PSK, SGT) in pumpkin roots and leaves at three time points (h post-inoculation, hpi) following inoculation with P. melonis in two resistant (Ghelyani and Tanbal), and two susceptible (Marmari and Khoreshti) varieties of pumpkin. Gene expression using quantitative real time PCR along a time course revealed the strongest transcriptomic response at 48 and 72hpi in resistant genotypes, 1.1-2.7-fold in roots and leaves, respectively, with a high significant correlation (r=0.857**-0.974**). We also found that CPI, PSK, SGT1 and POD act as a dual regulator that similarly modulate immunity not only against P. melonis, but also against other diseases such as early blight (Alternaria cucumerina), powdery mildew (Podosphaera xanthii), downy mildews (Pseudoperonospora cubensis), and pathogenic plant nematodes (Meloidogyne javanica). Furthermore, significantly higher activities of the ROS scavenging defence enzymes, catalase (1.6-fold increase) and peroxidase (6-fold increase) were observed in the roots of resistant cultivars at different hpi compared with non-inoculated controls. In addition, the biomass growth parameters including leaf and root length, stem and root diameter, root fresh weight and volume were significantly different among studied genotypes. Cumulatively, the transcriptome data provide novel insights into the response of pumpkins for improving pumpkin breeding to P. melonis.

Potential of 2-Hydroxyacetophenone Derivatives and Simple Phenol's for the control of Meloidogyne javanica

Objective: In this study, a series of synthetic hydroxylated (5-10) and prenylated (10-17) acetophenones, chalcones (18-20) and a flavone (21) have been synthesized and evaluated on the nematode Meloidogyne javanica. Additional phenolic compounds, including salicylic acid, isopropyl salicylate, thymol, carvacrol, cumic acid, eugenol, vanillin, and vanillic acid (22-29), were also tested. Methods: Compounds 5-21 have been synthesized by a sequence of reactions and were isolated and identified by 1H-NMR, 13C-NMR, and HRMS. The in vitro nematicidal effects of the compounds were tested on J2 juveniles. The nematicidal activity was confirmed by their egg hatching inhibition effects, tested at the minimum lethal concentration (minimum dose to give 100% J2 mortality). Results: Compounds 5-18 have been previously reported and 19-21 are described here for the first time. The 2´-hydroxylated acetophenones (5-9) showed strong nematicidal effects, being 7-9 the most active. Salicylic (22) and cumic (26) acids were effective compounds. Compounds 7, 12, 22-26, active on M. javanica J2 juveniles, were also egg hatching inhibitors. Conclusions: A C-2/C-4 dihydroxylation or C-2/C-4/C-3 trihydroxylation of the acetophenone moiety improved the activity, while introducing a hydrophilic isoprene chain (10-17) eliminated the effect, with only one prenylated acetophenone (12) being active. Among the additional phenolic compounds (22-29), these with a carboxyl group instead of the acyl side were better nematicides. These results generate molecular leads for developing new nematicidal phenolic compounds.

Organic residue controls Meloidogyne javanica and improves gas exchange and development in the gilo

Organic residue controls Meloidogyne javanica and improves gas exchange and development in the gilo