Juvenile Nematodes Research Articles

Evaluation of nematicidal potential of leaves extract of Afrohybanthus enneaspermus for management of Meliodogyne incognita in Tomato

The resistance of nematode pests to synthetic nematicides and its attendant hazards both to the crops and the ecosystem have caused growing interest. This study is aimed at investigating the nematicidal potential of the leaves extract of Afrohybanthus enneaspermus. Afrohybanthus enneaspermus is an evegreen shrub found in the tropical regions. The herbs have been used in ethonomedicine in the treatment of various ailments such as fever, diabetes, cough, skin infections and so on. According to standard methods in this study, in-vivo and In-vitro nematicidal screening of leaves extract was carried out against juvenile nematode pest (Meliodogyne incognita) while the pot experiment was carried out on tomato plants infected with root knot nematode. At the growth rate of the Tomato (Tropimech +), plant height was significantly lowered at 4 WAP (four weeks after planting) in tomato plants inoculated with 2,000 root-knot nematodes (RKN) applied with 20 g powered of Afrohybanthus enneaspermus compared with the rest of the treatments. With the application of 15% aqueous plant extracts and the inoculation of 2,000 RKN, plant height was significantly higher (32.8), followed by Plant alone and 20% aqueous plant extract. However, plant height was significantly lowered in plants applied with 20g powered of Afrohybanthus enneaspermus and nematode compared to the other treatments. At 6 weeks plant height is significantly higher in tomato plants inoculated with 5% aqueous plant extract with 2000RKN followed by others that are at the same range except 20g powered extract with 2000RKN that is significantly lowered . At 7 weeks plant height is significantly higher in tomato plants inoculated with 5% aqueous plant extract with 2000 RKN followed by others that are at the same range except 20g powdered extract with 2000 RKN that is significantly lowered. The research concluded that leaves extract of Afrohybanthus enneaspermus is effective in management of root Knot nematodes, however, in- vitro experiments, it is established that the powder form of the leave has higher effectiveness in management of nematode than its organic extract.

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

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

Entomopathogenic nematodes as a lethal bioagent to deter <i>Pieris brassicae</i> L. (Lepidoptera: Pieridae) infesting different cole crops: A review

Cole crops are the most important and attractive vegetables, belonging to the family Cruciferae are extremely grown all over the world. In India, their annual production has been reported to be about 191.77 million metric tons so chips into the economy by a huge amount. Pieris brassicae, one of the dreaded insect pests incur damage to different vegetables to a tune of 40%. To curb this pest damage various synthetic insecticides are applied, albeit showing promising results yet posing drastic negative imprints on non-target organisms, environment and pest resistance. These drawbacks demand a perfect alternative which seals all the glitches created by the chemical insecticides. For this Infective Juveniles (IJs) of Entomopathogenic Nematodes (EPNs) act as perfect biological agents. So, work done in these lines has been reviewed to facilitate students and researchers for advanced research related to entomopathogenic nematodes and P. brassicae.

Efficacy of Noval Nematicide on Root-knot Nematode, Meloidogyne javanica and Establishment of Recommended Dose in Mung Bean (Vigna radiata L.)

The study was carried out to efficacy of newer nematicide (fluensulfone 2% GR) at different doses under field conditions on mung bean. Total seven treatments were used with different doses of fluensulfone 2% GR i.e., T1 - fluensulfone 2% GR 10 kg/ha., T2 - fluensulfone 2% GR 12 kg/ha., T3 - fluensulfone 2% GR 14 kg/ha., T4 - fluensulfone 2% GR 16 kg/ha., T5- fluensulfone 2% GR 18 kg/ha., T6- fluensulfone 2% GR 20 kg/ha., T7 - carbofuran 3G 50 kg/ha and T8 - untreated check (control) maintained for comparison. The observations were recorded on plant growth characters (shoot length (cm), shoot weight (gm), root length (cm), and root weight (gm)) and nematode reproduction (number of galls per plant, number of egg mass per plant, number of eggs per egg mass, nematode juveniles per 200 cc soil and final nematode population). Treated plant with fluensulfone 2% GR with the dose of 20kg/ha found to be the best to given the maximum plant growth characters and minimized nematode reproduction.

Effect of male parental gamma irradiation on host suitability of its F1 progeny of a lepidopteran tropical pest, Spodoptera litura (Fabr.) towards development and virulence of entomopathogenic nematodes, Steinernema thermophilum

The suitability of F1 progeny insect larvae of the irradiated male parent, Spodoptera litura (Fabr.) for infective juveniles (IJs) of entomopathogenic nematodes (EPN), Steinernema thermophilum was assessed to comprehend the feasibility of combining EPNs with nuclear pest control tactic. As compared to the control, the IJs induced faster host mortality with reduced proliferation in F1 host larvae. IJs derived from F1 host larvae exhibited almost similar proliferation capacity on normal hosts as in control. Further, the molecular basis of EPNs induced mortality in F1 host larvae was evaluated. Dual stress of EPN infection and irradiation induced downregulation of the relative mRNA expression of antimicrobial genes and upregulated expression of antioxidative genes. A pronounced effect of EPNs in association with irradiation stress was apparent on host mortality. Radiation induced sterile F1 insect larvae of S. litura acted as a reasonably suitable host for EPNs and also provided the environment for developing viable EPNs for their potential use as biocontrol agents.

Exogenous application of different antagonists and their secretory metabolites to manage root-knot nematodes in pea

Pea (Pisum sativum L.) is a grain legume, a member of the Leguminosae family. Root-knot nematodes cause severe losses ranging from 15 to 85%. Different species of nematodes including root-knot nematodes reduce the yield of pea significantly. To control root-knot nematodes biological control is a more environment-friendly approach. The main objective of the study is to assess the effect of different antagonistic microbes and their secretory metabolites to manage root-knot nematodes in peas. Through this research, we aim to identify potential biological control agents that can be used as eco-friendly alternatives to chemical nematicides, contributing to sustainable pest management practices in agriculture. For this purpose, firstly, a brinjal seedling was transplanted for inoculum development which was inoculated with infective 2nd stage juveniles of root-knot nematodes (Meloidogyne spp.) in Department of Plant Pathology research area, University of Agriculture Faisalabad (UAF). Then two pea varieties viz. Matar sabaz and Pea-2009 were sown in pots and inoculated with nematode larvae after four weeks of sowing. Moreover, the management of nematodes was done by using the antagonists and their secretory metabolites application. The data of different plant growth and nematode-related parameters was taken and subsequently analyzed using analysis of variance and least significant difference test (LSD). Results showed that the antagonist’s treatment subsequently controlled root-knot nematodes (RKNs). Maximum plant/shoot length (47 cm), root length (25.25 cm), shoot weight (22.25 g) pod length (8.50 cm), No. of secondary shoots (8) and minimum number of galls (2.5 cluster), was observed in plants treated with Bacillus spp. (T1) while maximum No. of fruits (5.75) was observed in plants treated with Pseudomonas spp. (T2). Similarly, the number of nodules (7.50 clusters) primary shoots (5) Root weight (4.6 g) was observed in plants treated with Enterobacter spp. (T3).

Compuestos bioactivos de bacterias y hongos en el control de nematodos fitopatógenos: mecanismos de acción, interacciones y aplicaciones

Phytopathogenic nematodes are a threat for agriculture, they cause plant diseases and economic losses worldwide. Currently, the pursuit of compounds of biological origin for nematode biocontrol has become a priority as an environmentally friendly alternative. Microorganisms-derived compounds have several strategies to reduce the populations of infectious juvenile nematodes. Although microorganisms and their metabolites are the focus of literature reports reviews on nematicidal control, interactions between fungi, bacteria, and nematodes, as well as the compounds that are generated in such interactions, are not highlighted. The aim of this review was to discuss the latest advances on chemical compounds secreted by microorganisms and their interaction mechanisms for biological control of phytopathogenic nematodes. Results were organized based on: i) mode of action, ii) infection process, iii) nematicide compounds, iv) interactions and field applications, and v) current challenges. The scope of this review contributes to a better comprehension of the versatility of bacterial and fungal compounds for their use in the development of management plans for nematode control.

Screening of cauliflower (Brassica oleracea var. botrytis L.) genotypes for resistance to the root-knot nematode (Meloidogyne incognita)

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.

Isolation of Pasteuria penetrans, an obligate hyper-parasite, infecting root knot nematode, Meloidogyne spp. from the rhizosphere of pulses in India

BackgroundPasteuria penetrans is a mycelial, endospore forming, obligate, bacterial parasite that has shown enormous potential for biological control of root-knot nematode, Meloidogyne spp. In the present study, the effort has been made to isolate effective and high temperature tolerant indigenous strains from pulse rhizosphere in India.ResultsSurveys were carried out in four different agro-climatic zones and collected 106 root-knot nematode infected soil and plant samples from pulses rhizosphere. Of these, we observed Pasteuria spore attachment on root knot nematode juveniles from seven samples: three from Varanasi, two from Salem and one each from Deoria and Kushinagar. The pure cultures of these seven isolates (named as IIPR-Pp-1 to IIPR-Pp-7 from single infected female, respectively) were developed in 7 cm pot and soil-less CYG medium. The nematode host species was identified as Meloidogyne incognita by perineal pattern and confirmed by sequencing of ITS region. The host range study with M. incognita and Heterodera cajani showed the spore attachment was specific to M. incognita revealed that the species of the parasite was Pasteuria penetrans. SEM study on morphometrics of Pasteuria spores belong to two groups. In vitro assay on endospore attachment assay with pre-treated endospores at 20, 30, 40, 50, 60 and 70 °C revealed that maximum number of endospore attachment of all isolates was observed at 30 °C followed by 40 °C, and the least number of them was observed at 60 °C and above. The isolate Pp3 exhibited maximum number of spore attachments among all isolates at 30 °C treatment (14) and 40 °C treatment (10.67). Endospore attachment assay with pre-treated J2 at 20, 25, 30, 35, 40 and 45 °C revealed that maximum number of attachment of all isolates was observed at 30 °C treatment, and no attachment was observed at 40 °C and above.ConclusionPasteuria penetrans isolate IIPR-Pp3 exhibited high temperature tolerance and can be used further to develop Pasteuria-based biopesticide for management of root-knot nematode, M. incognita in pulses.

NEW EXTRACTION METHOD OF ENTOMOPATHOGENIC NEMATODES USING THE BASIC FLOTAC AND THE MINI-FLOTAC TECHNIQUES

The FLOTAC basic technique is a recognised method used mainly in the veterinary field to extract parasites from the faeces of animals found in the stomach and intestine. This study is the first application of the FLOTAC and Mini-FLOTAC techniques to extract infective juveniles of entomopathogenic nematodes from infested Galleria mellonella. The EPN used for this purpose was an endemic Italian nematode belonging to the Rhabitidae family Steinernema carpocapsae. Galleria mellonella larvae were infected and extraction was performed a few days after infection using both techniques. A comparison was then made between the two methods. The results showed that infective juveniles could be extracted from the infected larva as early as three days after infection. The difference between the FLOTAC basic technique and the Mini-FLOTAC technique was not significant in the extraction of entomopathogenic nematodes. Due to its sensitivity and operating easiness the Mini-FLOTAC technique is a promising method for the extraction of entomopathogenic nematodes. It allows faster extraction of nematodes from the inhabited soil and insect host than the conventional White trap method. Key Words: Microbial biocontrol, Entomopathogenic nematodes, Nematode extraction, FLOTAC, Mini-FLOTAC

Indigenous Populations of a Biological Control Agent in Agricultural Field Soils Predicted Suppression of a Plant Pathogen.

The nematophagous fungus Hyalorbilia oviparasitica and relatives (Hyalorbilia spp.) are known to parasitize several endoparasitic nematodes. In this project, we hypothesized that indigenous populations of this fungus could be used to predict nematode suppression in agricultural field soils. We quantified Hyalorbilia spp. in soil samples from 44 different sugar beet fields in the Imperial Valley of California. Seven soils harboring Hyalorbilia spp. and two that tested negative for the fungi were examined for nematode suppressive activity. Untreated and autoclaved portions of each soil were planted with cabbage and infested with sugar beet cyst nematode (Heterodera schachtii) juveniles. Females and cysts of H. schachtii were enumerated after 12 weeks. In the seven soils harboring Hyalorbilia spp., females and cysts in the untreated soils were reduced by 61 to 82% compared with the autoclaved controls. Soils with no detectable Hyalorbilia spp. exhibited no nematode suppression. Two novel Hyalorbilia strains, HsImV25 and HsImV27, were isolated from H. schachtii females reared in field soil using an enrichment and double-baiting cultivation technique. Both strains suppressed H. schachtii populations by more than 80% in soil-based assays, confirming that Hyalorbilia spp. are the likely causal agents of the nematode suppression in these soils. This study demonstrated that indigenous populations of a hyperparasite (Hyalorbilia spp.) in agricultural field soils predicted suppressive activity against a soilborne plant pathogen (H. schachtii). To our knowledge, this is the first report to demonstrate this capability. We anticipate that this research will provide a blueprint for other similar studies, thereby advancing the field of soilborne biological control.

Application of herbicides in green cover crops to reduce Meloidogyne javanica inoculum in soybean plants

Nematodes are among the main plant parasites affecting Brazilian agriculture. Management practices involving the use of antagonistic or non-host plants are crucial for combating Meloidogyne javanica populations in the country. However, there is still limited information on the effects of herbicides on nematode populations. The aim of this research was to evaluate the impact of herbicides applied to crops on M. javanica populations in soybean and to examine the direct effect of herbicide products on the hatching of nematode juveniles. We conducted greenhouse and in vitro experiments. In the greenhouse experiment, soybean plants were grown in pots with sterile substrate, and a soybean seed was inoculated with 2000 nematodes per plant. The plants grew for 60 d, after which they were cut, and the following cover crops were planted: Crotalaria spectabilis, pigeon pea (Cajanus cajan), Stylosanthes, and buckwheat (Fagopyrum esculentum) for 60 d. These cover crops were desiccated with one of the following three herbicides: fomesafen, chlorimuron, or bentazone. Subsequently, soybeans were replanted and cultivated for additional 60 d. In vitro assays were used to determine the hatching percentage of M. javanica eggs exposed to herbicides. Both tests were repeated at different times of the year (Trials 1 and 2). Meloidogyne javanica reproduction was higher on soybean crops grown when buckwheat was a cover crop. Herbicide application reduced total nematode numbers in soybean grown in succession to buckwheat compared with the untreated control. The vegetative development of soybean crops was negatively influenced by herbicide treatment of cover crops, especially with the use of chlorimuron. Bentazone and fomesafen did not affect nematode hatching in vitro.

Antinemic Metabolites of Simarouba glauca against Root Knot Nematode, Meloidogyne incognita Infesting Groundnut, Arachis hypogaea

Background: Groundnut, Arachis hypogaea is a leguminous crop grown in tropical and subtropical regions of the world. Meloidogyne spp., is considered to be nematode pest of economic importance for the groundnut throughout the world. Plant metabolites with nematicidal property have been in use for a long time for nematode control that offer many environmental advantages. Methods: The nematicidal activity of methanolic leaf extract of Simarouba glauca on eggs and juveniles (Js) of root-knot nematode, Meloidogyne incognita infesting vegetables was evaluated at three concentrations in vitro (100%, 50%, 25%) with control at three exposure times. Result: Results revealed that at 100% concentration, the methanolic leaf extract of S. glauca showed the least number of eggs hatched (7.85, 12.63, 16.30/egg mass) and the highest mortality (60.58, 70.23, 92.58/100 juveniles) at the exposure times of 24 hrs, 48 hrs, 72 hrs, respectively. The phytochemical compounds viz., Hexadecanoic acid-methyl ester, Isopropyl palmitate, Octadecanoic acid and Methyl stearate detected through GC-MS profiling of methanolic extract of S. glauca were found to inhibit the nematode activity. Pot and field studies proved that soil application of Simarouba leaf powder @ 10 g/plant and 5 kg/ha reduced the nematode infestation. This study implies that use of Simarouba leaf powder produces nematicidal effect against plant parasitic nematodes and reduced the nematode infestation in groundnut and is more suitable candidate in the context of biological control.

Manipulation of GameXPeptide synthetase gene expression by a promoter exchange alters the virulence of an entomopathogenic bacterium, Photorhabdus temperata temperata, by modulating insect immune responses.

An entomopathogenic bacterium, Photorhabdus temperata subsp. temperata, is mutualistic to its host nematode, Heterorhabditis megidis. The infective juvenile nematodes enter target insects through natural openings and release the symbiotic bacteria into the insect hemocoel. The released bacteria suppress the insect immune responses and cause septicemia through their secondary metabolites. GameXPeptide (GXP) is one of the common secondary metabolites of most Photorhabdus species and is produced by the catalytic activity of a specific non-ribosomal peptide synthetase called GxpS encoded by the gxpS gene. This study confirmed gxpS to be encoded in the P. temperata temperata genome and analyzed its expression during bacterial growth. LC-MS/MS analysis of the bacterial culture broth contained at least four different GXPs (GXP-A to GXP-D), in which GXP-A was the most abundant. To investigate GXP synthesis following gxpS expression, the gxpS promoter of P. temperata temperata was replaced with an inducible arabinose promoter by homologous recombination. The gxpS transcript levels in the mutant were altered by the addition of l-arabinose. Without the inducer, the gxpS transcript level was significantly lower compared to the wild type and produced significantly lower amounts of the four GXPs. The addition of the inducer to the mutant significantly increased gxpS expression and produced significantly higher levels of the four GXPs compared to the wild type. The metabolite extracts obtained from wild-type and mutant bacteria showed differential immunosuppressive activities according to their GXP contents against the cellular and humoral immune responses of a lepidopteran insect, Spodoptera exigua. Interestingly, the gxpS-mutant bacteria showed less insecticidal activity compared to the wild type, whereas the addition of GXP to the mutant significantly restored insecticidal activity. These results suggest that the gxpS gene encoded in P. temperata temperata is responsible for the production of at least four different GXPs, which play crucial roles in bacterial virulence.

Phytochemical profiling and nematicidal activity of leaf extracts of Tinosporacordifolia against reniform nematode (Rotylenchulus reniformis)

Reniform nematode, Rotylenchulus reniformis is an important nematode associated with castor influencing the productivity of the crop. Efficacy of the leaf extract of Tinospora cordifolia at different concentrations viz., 0.1, 0.5, 1.0, 2.0, 5.0, 10.0 and 20% against the nematode juveniles were evaluated in vitro. The extract, at 20% concentration was recorded to be effective in the reduction of nematode juveniles to 93.8 per cent. The more active non-polar and medium polar compounds which are having melting point less than 200o C were analysed by GC-MS. Eighteen compounds of the total extract were identified of which six compounds were reported to possess nematicidal properties.

Assessment of Entomopathogenic Nematodes in Oil Emulsions to Control Scyphophorus acupunctatus in Agave under Laboratory Conditions

The weevil Scyphophorus acupunctatus Gyllenhal causes damage and losses in agave crops and has traditionally been controlled using contact and systemic agrochemicals. Implementing microbial control strategies is proposed as an alternative to mitigate the environmental impact associated with agrochemicals. The objective of this study was to determine the survival of entomopathogenic nematodes in oil emulsions for the control of adult S. acupunctatus. Three species of entomopathogenic nematodes were evaluated: Steinernema carpocapsae, S. glaseri, and Heterorhabditis bacteriophora. We used two concentrations (50 ± 5 and 100 ± 10 infectious juvenile nematodes), and oil emulsions derived from Salvia hispanica, Triticum vulgare, and Olea europea with oil purity of 20% and 40%. The effectiveness of these treatments was assessed by determining the mortality rate of S. acupunctatus. The results indicate that the combination of S. glaseri and H. bacteriophora, at concentrations of 50 ± 5 and 100 ± 10 nematodes, respectively, with T. vulgare and O. europea oils, achieved a mortality rate of 85.76% in S. acupunctatus adults at 24 h. At 120 h, a mortality rate of 100% was achieved with specific formulations, such as S. glaseri with 100 ± 10 nematodes + O. europea, and H. bacteriophora with 100 ± 10 nematodes + O. europea. Consequently, we conclude that oil formulations combined with nematodes show potential as an effective and environmentally friendly alternative for the control and management of S. acupunctatus.

Application of Rhizopus microsporus and Aspergillus oryzae to enhance the defense capacity of eggplant seedlings against Meloidogyne incognita

Several phytopathogens attack eggplant, causing crop damage. One of the most destructive plant diseases, Root-Knot Nematode (RKN), causes significant damage to eggplant seedlings. Finding safe and effective biological alternatives to prevent eggplant root nematode disease, which significantly limits plant productivity, is the innovative aspect of this study. Six isolates of plant growth-promoting fungus (PGPF) were tested in the current work for improving biochemical defense and physio-biochemical performance in eggplant seedlings under the Meloidogyne incognita challenge. PGPF isolates were tested in vitro for some biochemical traits such as Siderophores and HCN production. Besides, the antagonistic efficacy of PGPF filtrates against M. incognita was tested in vitro. The best isolates capable of producing HCN were F5 and F3 respectively. Also, F5 followed by F3 exhibited the maximum mortality proportions of 74.20% and 60.35% mortality in nematode juveniles after 96 hours respectively. Moreover, F5 has the highest level of antioxidant activity, with IC50 145 µg/mL followed by F3 with IC50 350 µg/mL. thus, we identified F5 and F3 completely as Rhizopus microsporus (OQ291571.1 and Aspergillus oryzae OQ291572.1. Implementing R. microsporus and A. oryzae collectively in vivo study was the most successful therapy, limiting nematode recordings as 95.23%, 86.98%, 80.35%, 80%, and 68.78% reduction in females, galls, developmental stage, egg masses, second juveniles, respectively, in diseased seedlings. It could be suggested that the use of ethyl acetate extracts (EAE) of A. oryzae and R. microsporus might be commercially applied as a stimulator of eggplant and or anti-nematodes against M. incognita.

Activity of Root-Knot Nematodes associated with Composition of a Nematode-Attached Microbiome and the Surrounding Soil Microbiota.

We investigated if activity of the pre-infective juveniles (J2s) of root-knot nematodes is linked to the recruitment of a specific microbiome on the nematode surface and/or to the composition of the surrounding microbiota. For this, we determined the J2 activity (active vs. non-motile that referred to dead and immobile J2s) upon a 3-day incubation in soil suspensions and studied the composition of bacteria, protists and fungi present on the nematode surface and in the suspensions using amplicon sequencing of the 16S/18S rRNA genes, and ITS region. We also amended suspensions with n CHA0 to study its effects on J2 activity and microbial composition. The J2 activity was suppressed in soil suspensions, but increased when suspensions were amended with P. protegens CHA0. The active and non-motile J2s differed in the composition of surface-attached bacteria, which was altered by the presence of P. protegens CHA0 in the soil suspensions. The bacterial genera Algoriphagus, Pedobacter and Bdellovibrio were enriched on active J2s and may have protected the J2s against antagonists. The incubation time appeared short for attachment of fungi and protists. Altogether, our study is a step forward in disentangling the complex nematode-microbe interactions in soil for more successful nematode control.

Positive Chemotaxis of the Entomopathogenic Nematode Steinernema australe (Panagrolaimorpha: Steinenematidae) towards High-Bush Blueberry (Vaccinium corymbosum) Root Volatiles

The foraging behavior of the infective juveniles (IJs) of entomopathogenic nematodes (EPNs) relies on host-derived compounds, but in a tri-trophic context, herbivore-induced root volatiles act as signals enhancing the biological control of insect pests by recruiting EPNs. In southern Chile, the EPN Steinernema australe exhibits the potential to control the raspberry weevil, Aegorhinus superciliosus, a key pest of blueberry Vaccinium corymbosum. However, there is no information on the quality of the blueberry root volatile plume or the S. australe response to these chemicals as putative attractants. Here, we describe the root volatile profile of blueberries and the chemotaxis behavior of S. australe towards the volatiles identified from Vaccinium corymbosum roots, infested or uninfested with A. superciliosus larvae. Among others, we found linalool, α-terpineol, limonene, eucalyptol, 2-carene, 1-nonine, 10-undecyn-1-ol, and methyl salicylate in root volatiles and, depending on the level of the emissions, they were selected for bioassays. In the dose–response tests, S. australe was attracted to all five tested concentrations of methyl salicylate, 1-nonine, α-terpineol, and 2-carene, as well as to 100 µg mL−1 of 10-undecyn-1-ol, 0.1 and 100 µg mL−1 of linalool, and 100 µg mL−1 of limonene, whereas eucalyptol elicited no attraction or repellency. These results suggest that some volatiles released from damaged roots attract S. australe and may have implications for the biocontrol of subterranean pests.

Agro-industrial waste and a nematicidal substance therein (triethyl phosphate) are effective against Meloidogyne incognita of bananas

Meloidogyne are a group of plant-parasitic nematodes that cause very large yield losses of agricultural crops globally. Banana plants are susceptible to Meloidogyne, which are mainly controlled by chemical nematicides. However, these harm the environment and human health, and their use is thus being restricted. This study developed novel sustainable practices to control root-knot nematodes in banana production. Chicken manure and cassava ethanol wastewater are common agro-industrial wastes. After fermentation, both fermentation broths reduced Meloidogyne incognita infection by killing the second-stage juvenile nematodes and inhibiting egg hatching. The fermentation broths also decreased root galls and the soil nematode density. We used gas chromatography−mass spectrometry to identify triethyl phosphate as the nematicidal compound; this inhibited egg hatching and promoted juvenile mortality in Meloidogyne incognita. In terms of nematode control, both fermentation broths provided the nutrients necessary for banana growth and improved the nutrient contents of banana plants. Both fermentation broths (2–10%) and triethyl phosphate (0.5–4.0 mM) have no effects on non-target organism Caenorhabditis elegans. Collectively, our results contribute a safe strategy for nematode management, recycling of agro-industrial waste, and improving the sustainability of banana production.