Tylenchulus semipenetrans is a soil-borne pathogen that causes substantial damage and economic losses to citrus crops worldwide. Due to the high toxicity of chemical nematicides to humans and the environment, biocontrol bacteria have emerged as a promising alternative for managing citrus nematodes. This study aimed to screen bacterial strains for their efficacy to control T. semipenetrans and assess their impact on citrus plant growth. A total of 107 bacterial strains were isolated from the soil and roots of infested citrus trees. Among these, five strains exhibited significant nematicidal activity against T. semipenetrans. Four bacterial densities were tested for each strain: 3.6 x 10(5), 2.5 x 10(4), 3.6 x 10(3), and 1.2 x 10(3) cells/ml. These strains were tested both individually and in combination to evaluate their efficacy. The five strains were identified as Variovorax paradoxus, Bacillus pseudomycoides, Bacillus simplex, Bacillus cereus, and Paracoccus speluncae based on physiological, biochemical, and molecular (16S rRNA gene sequences) analyses. Juvenile mortality (J2s) and egg hatching inhibition were positively correlated with bacterial concentration and exposure duration. The highest juvenile mortality (100%) was observed with a combination of all five bacteria (3.6 x 10(5) cells/ml) after 96 h, while B. cereus alone achieved 98.98% mortality. The maximum nematicidal activities of the bacterial filtrates were generally observed between the 4th and 6th days of incubation, coinciding with peak bacterial growth and biomass production. The selected isolates also demonstrated the ability to produce indole acetic acid and solubilize phosphorus. In greenhouse experiments, the five isolates reduced T. semipenetrans populations by up to 62.96% compared to the control. Additionally, all rhizosphere bacteria and their combination significantly enhanced plant growth parameters (p < 0.0001). Notably, P. speluncae BR21 has not previously been tested for nematicidal effects on any nematode, making this the first documented report of its nematicidal potential.

This study investigated the infestation of tomato plants by the plant-parasitic nematode, M. incognita, and its accurate detection by plant electrophysiology (PE). Dedicated tests were done on whole plants to record electrophysiological signals from nematode infested and uninfested plants and to establish a trained model indicating nematode-induced stress. Monitoring nematode-induced stress by PE confirmed the results obtained by assessing root galls and quantifying xylem sap 3 to 4 weeks after infestation. The machine learning model captured the stress intensities and the time course of plant damage caused by nematodes. Stress caused by second-stage juveniles (J2) infestation appeared 3 to 5 days after infestation (DAI), whereas stress caused by egg infestation was detected 5 to 7 days later (10-13 DAI). For the first time, the real-time effectiveness of nematicides was recorded in further tests. Nematode infested plants treated preventatively with cyclobutrifluram (TYMIRIUM (R) technology) showed a delayed and short (about 3 days) period of low stress intensity, whereas infested but untreated plants showed a period of maximum stress for about 12 days. In addition, depending on the type of application (preventative or curative), different modes of biological activity of IRAC group N-2 and N-3 nematicides (fluopyram, abamectin) could be captured by PE signalling. PE offers a new way of monitoring plant health in real time, which is particularly valuable for accessing 'invisible' pests, such as plant-parasitic nematodes in the soil.

Root-knot nematode (RKN) (Meloidogyne incognita) is a major plant parasitic nematode that severely damages crops, leading to significant yield losses and substantial economic impact globally. This study aims to investigate an environmentally sustainable biological strategy for mitigating parasitic populations of the root-knot nematode, M. incognita. Specifically, the research focuses on assessing the nematicidal efficacy of Acalypha indica against M. incognita mortality and second-stage juveniles' (J2) hatching under controlled in vitro conditions. A. indica leaf aqueous extract was applied at varying concentrations (250, 500, 750, and 1000 ppm) to J2s and egg masses of M. incognita. Notably, at 1000 ppm, a significant increase in J2 mortality and hatching inhibition was observed, while 250 ppm concentration showed the least favorable outcome; with mortality rates ranging from 22-82%. Chemical analysis via gas chromatography-mass spectroscopy (GC-MS) identified Benzoic acid, Cyclooctasiloxane, and 3-Isopropoxy-1,1,1,7,7,7-hexamethyl-3,5,5-tris (trimethylsiloxy) tetrasiloxane as predominant compounds. The nematicidal activity of A. indica leaf extract was further validated through in silico molecular docking, revealing that benzoic acid, Cyclooctasiloxane, and 3-Isopropoxy-1,1,1,7,7,7-hexamethyl-3,5,5-tris (trimethylsiloxy) tetrasiloxane bind to the ODR 3 protein of M. incognita with binding energies of -15.72, -8.91, and -7.35 kJ/mol, respectively. These findings hold promise for environmentally benign root-knot nematode management, contributing to improved soil health.

Plant-parasitic nematodes (PPN) pose a significant threat to agricultural productivity by causing extensive damage to various crops worldwide. Their complex life cycle and ability to persist in soils make nematode management difficult. Chemical control strategies are emerging as effective but often result in environmental and ecological risks. Biocontrol agents offer a promising alternative with the desired level of reduction in nematode populations without harming non-target organisms. Among the nematode antagonists, Streptomyces spp. is an effective candidate with their ability to produce secondary metabolites that exhibit potent nematicidal properties. Streptomyces avermitilis is the one species that has been completely exploited for nematode and insect management. This review highlights the role of Streptomyces spp. other than S. avermitilis in phytonematode management. Few Streptomyces spp. such as S. yatensis, S. pactum, S. rochei, S. rubrogriseus, S. lincolnensis, S. hygroscopicus, S. antibioticus strain M7, S. albogriseolus ND41 and S. fimicarius D153 are reported to have nematode control potential. Arenimycin, carboxamycin, fervenulin, hygromycin, and lincomycin are some of the Streptomyces-derived compounds that proved to have nematicide potential. Streptomyces spp. also acts as an elicitor of plant defense against nematode intruders. They evinced endophytic potential, plant growth promotion mechanism, compatible nature with other antagonists, and safe to non-target organisms. This current review also highlights the direct and indirect mechanisms by which they control nematodes, another beneficial role in plants, and strategies to upgrade them as commercial products in future thrust areas.

This study investigates the efficacy of Trichoderma spp. and Bacillus spp., as well as their gamma radiation-induced mutants, as potential biological control agents against Meloidogyne javanica (Mj) in tomato plants. The research encompasses in vitro assays, greenhouse trials, and molecular identification methodologies to comprehensively evaluate the biocontrol potential of these agents. In vitro assessments reveal significant nematicidal activity, with Bacillus spp. demonstrating notable effectiveness in inhibiting nematode egg hatching (16-45%) and inducing second-stage juvenile (J2) mortality (30-46%). Greenhouse trials further confirm the efficacy of mutant isolates, particularly when combined with chitosan, in reducing nematode-induced damage to tomato plants. The combination of mutant isolates with chitosan reduces the reproduction factor (RF) of root-knot nematodes by 94%. By optimizing soil infection conditions with nematodes and modifying the application of the effective compound, the RF of nematodes decreases by 65-76%. Molecular identification identifies B. velezensis and T. harzianum as promising candidates, exhibiting significant nematicidal activity. Overall, the study underscores the potential of combined biocontrol approaches for nematode management in agricultural settings. However, further research is essential to evaluate practical applications and long-term efficacy. These findings contribute to the development of sustainable alternatives to chemical nematicides, with potential implications for agricultural practices and crop protection strategies.

Meloidogyne incognita is believed to be the most devastating pest causing severe damage to crops, and hence, innovative and effective means of controlling the nematode is the need of the day. The focus of the current study is to devise an effective and innovative myco-fabrication of MgO nanoparticles (NPs) along with melatonin for ef ficient management of M. incognita infecting tomatoes. Fungal extracts were used to synthesize the myco-fabricated NPs through a green synthesis pathway and were veri fied using different spectroscopic means. The nanoparticles exhibited appreciable nematicidal potential, such as drastic egg hatch inhibition and juvenile mortality under in vitro assays. Evaluation of NPs and melatonin in planta, alone or combined form, was investigated on tomato plants already inoculated with M. incognita . The alterations in the nematode population on roots of plants as well as in soil, growth parameters, and biochemical attributes of plants were recorded. A signi ficant reduction in nematode population was revealed on the application of melatonin and myco-fabricated nanoparticles, hence exhibiting an improvement in the plant 's biochemical (glutathione, phenolic, flavonoid, and antioxidant enzymes) and growth parameters. A synergistic impact was shown on the combined application of the treatments. Furthermore, an enhancement in the expression as well as activities of antioxidant enzymes was also observed. Increased resistance of plants against nematodes resulted in connection with the improved antioxidant status of plants due to this combined treatment. The signi ficantly improved growth of plants under M. incognita stress conditions reveals the potential of the proposed treatments having synergistic interaction to manage phyto-parasitic nematodes effectively. This presents innovative means of agricultural biotechnologies that have the potential to contribute to the ef fi- cient management of nematodes infecting plants. (c) 2024 SAAB. Published by Elsevier B.V. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

The dynamic of plant-parasitic nematode populations in soil is closely related to soil microorganisms. Fungi from Heterodera zeae cysts were isolated to explore the phenomenon of decline in the H. zeae population in the soil. Phylogenetic study of partial ITS, BenA, CaM, and RPB2 gene sequences, in addition to morphological investigations, was utilized to identify a nematode-destroying fungus. The nematicidal activity of a novel strain GX1 against H. zeae was assessed in vitro and in the greenhouse. Our findings revealed that strain GX1 is a new species of Talaromyces, named Talaromyces cystophila. It has a strong parasitic and lethal effect on H. zeae cysts, with 91.11% parasitism on cysts at 3 days after treatment. The contents of second-stage juveniles (J2s) and eggs inside the cysts were degraded and formed dense vacuoles, and the damaged eggs could not hatch normally. The spore suspension exhibited high nematophagous activity against nematodes, and fermentation filtrate exhibited marked inhibition of egg hatching and nematicidal activities on J2s. The hatching inhibition rates of eggs exposed to 1 x 10(8) CFU/ml spore suspensions or 20% 1-week fermentation filtrate (1-WF) for 15 days were 98.56 and 100%, respectively. The mortality of J2s exposed to 1 x 10(8) CFU/ml spore suspension reached 100% at 24 h; exposure to 50% 2-WF was 98.65 and 100% at 24 and 48 h, respectively. Greenhouse experiments revealed that the spore suspension and fermentation broth considerably decreased H. zeae reproduction by 56.17 to 78.76%. T. cystophila is a potential biocontrol strain with nematophagous and nematicidal activity that deserves attention and application.