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Summary
A new genus is proposed to accommodate an undescribed dorylaimid form collected in Iran. Persianema gen. n. is characterised by its three-layered cuticle, oral field appreciably sunken but its perioral area visibly protruding, odontostyle less than one-half of lip region diam. and with large aperture, guiding ring simple and always located in front of odontostyle, odontophore 4-5 times longer than odontostyle, dorsal gland nucleus (DN) very posteriorly located, female genital system di-ovarian with well-developed pars refringens vaginae, tail short and rounded in both sexes, spicules dorylaimid and 3-4 spaced ventromedian supplements with hiatus. Its type and only species, P. enigmaticum sp. n., is described and illustrated, including SEM observations. It is distiguished by its 1.45-2.03 mm long body, lip region offset by shallow depression and 15.5-17.5 μm wide, odontostyle 6-7 μm long with aperture occupying more than half of its length, neck 285-340 μm long, pharyngeal expansion 38-43% of the total neck length, three gland cells present at pharyngo-intestinal junction, simple uterus 81-113 μm or 1.7-3.1 body diam. long, transverse vulva (V = 50-54), tail 15-25 μm long (c = 69-106, c′ = 0.6-0.8) and spicules 38-48 μm long. Molecular analysis of D2-D3 28S rDNA sequences revealed its closest similarity with Pungentus sequences, and an integrative comparison supports its belonging to Pungentinae.
Summary
Purpureocillium lilacinum is a potent biocontrol agent against Meloidogyne spp. and various other plant-parasitic nematodes in crops. However, existing commercial formulations of P. lilacinum suffer from drawbacks like short shelf life and inconsistent performance in different environmental conditions. To address these issues, a new nano-formulation of P. lilacinum was developed and tested against Meloidogyne incognita infecting tomatoes. Initially, edible oil-based emulsions were prepared using probe ultrasonication, with 40 formulations screened and 14 selected for further testing. Seven of these emulsions remained stable at room temperature (28 ± 4°C) for 8 weeks, with stability assessed based on particle size, zeta potential, and particle shape using particle size analysis and transmission electron microscopy (TEM). Among these, NE 8 (comprising 10 ml of 1% carboxyl methyl cellulose (CMC), 1.25 ml of Tween 80 and 5 ml of sunflower oil) exhibited superior characteristics, with an average particle size of 226.6 nm, a zeta potential of −54.80 mV, and a spherical morphology under TEM examination. The P. lilacinum nanoemulsion formulation was produced by homogenising NE 8 emulsion and spores at a 1:1 ratio, ensuring efficient spore dispersion and encapsulation without loss of viability. In vitro tests demonstrated 100% immobility of M. incognita second-stage juveniles (J2) and 100% parasitism of eggs at a concentration of 5.0 ml l−1. Under glasshouse conditions, soil drenching with the nano-formulation at concentrations ranging from 0.5 to 5.0 ml l−1 resulted in enhanced tomato growth and significant suppression of M. incognita populations in soil and roots, with increased egg mass parasitism. Bio-safety tests confirmed that P. lilacinum nano-formulation at concentrations of 0.25 ml l−1 and 5.0 ml l−1 had no harmful effects on the earthworm Eudrilus eugeniae.
Summary
Two species of the genus Tricirronema: T. tamdaoense and T. tentaculatum, are studied from agricultural soils of Vietnam. Both species are morphologically and morphometrically characterised based on LM and SEM studies. These species are mainly differentiated by the morphology of the vagina, sigmoid in T. tamdaoense and straight in T. tentaculatum, and males with more robust spicules in T. tamdaoense. SEM studies of both species are provided. Molecular analysis based on 18S and 28S rDNA fragments is included for T. tentaculatum, showing relationship with members of the genus Eucephalobus. In addition, a key to species identification of the genus Tricirronema is included, as well as illustrations and a compendium table with the main measurements of the three species.
Summary
A new species, Pratylenchus platyceriumis sp. n., was intercepted in the roots and rhizosphere of Platycerium spp. imported from Thailand. It is characterised by sexual adults with lip region containing two annuli, the lateral field with four equidistant lines, partially areolated, the female stylet (16.5-18.7 μm) robust with broadly rounded knobs, V = (70.2-79.2), with a large oval spermatheca often full of sperm, tail subcylindrical to conoid, and terminus obliquely truncated to conical with variable mucrons or projections. Male spicules are arch-shaped, the gubernaculum trough-shaped, the tail conoid, with tip narrow and pointed and bursa striated instead of crenate. The new species is close to Pratylenchus coffeae, P. dakotaensis, P. goodeyi, P. gutierrezi, P. horti, P. morettoi, P. okinawaensis, P. panamaensis, P. pratensis, P. pseudocoffeae, P. speijeri, P. yamagutii and P. ventroprojectus, but different. Phylogenetic analyses using D2-D3 expansion domains of the 28S rRNA gene, the ITS region, the partial 18S rRNA gene and the mitochondrial cytochrome oxidase subunit I (COI) gene confirm its classification as a new species.
Summary
The chlamydospore production of three Pochonia chlamydosporia isolates from two different varieties was evaluated on flaxseed and rice husk, testing their survival on talc, kaolin and maize cob powder. The effect of each formulation in suppressing Meloidogyne javanica on tomato was also investigated in glasshouse trials. For all isolates, the number of chlamydospores produced on flaxseed was about twice that observed on rice husk (i.e., 8 weeks after inoculation, isolate IRAN 1119 C produced 98 × 106 and 50 × 106 chlamydospores on flaxseed and rice husk, respectively). Isolate IRAN 1212 C produced more chlamydospores with longer lifespan compared with the other fungi. IRAN 1212 C on maize cob powder could reduce M. javanica by 95% at a level similar to fluopyram. This prototype formulation had a superior effect in establishing the fungus in the rhizosphere and on roots, suppressing the nematode and increasing plant growth. The three P. chlamydosporia isolates reproduced well on flaxseed and could last longer if formulated on maize cob powder, which appears suitable to produce an effective powdered formulation.
Summary
The root-knot nematode Meloidogyne izalcoensis was described parasitising coffee trees and causing damage in the Izalco volcano region, Sonsonate, El Salvador. In Brazil, it was detected in coffee roots in the municipality of Indianópolis, Minas Gerais state (MG). Intercropping cover crops is a traditional practice in Brazilian coffee orchards, and the use of plants that are non-hosts or antagonistic to the nematodes is a very promising strategy for coffee in infested areas. Due to the scarce information on the host status of M. izalcoensis, the aim of this study was to evaluate 24 plants of different species of cover crops and select the non-hosts or poor hosts. Two assays were conducted at different times, and all plants were inoculated with 10 000 eggs. After 90 days, the following parameters were determined: fresh root weight, reproduction factor (RF) and final reaction. Plants with RF < 1.0 were classified as non-hosts (NH), those with RF > 1.0 were classified as hosts and using statistical analyses as: good host (GH), intermediate host (IH) and poor host (PH). Most of the botanical species tested were classified as NH or PH to M. izalcoensis: cotton, rice, white oat, black oat, ryegrass, corn, three species of grass, two cultivars of millet, two wheat cultivars, Crotalaria breviflora, C. ochroleuca, C. spectabilis, jack bean, gray mucuna bean and two species of rice grass. Only tomato and bean were classified as GH, and C. juncea and soybean were classified as IH. The plants identified as non-hosts or poor hosts can be recommended for intercropping or for crop rotation in Brazilian coffee orchards in regions infested by M. izalcoensis.
Summary
Bursaphelenchus xylophilus is the causative agent of pine wilt disease and is indigenous to North America. It has been introduced into Japan where the non-pathogenic close relative, B. mucronatus, is widely distributed. Both nematode species have similar life cycles with vectors of cerambycid beetles of the genus Monochamus. When interspecific hybrids are backcrossed with B. xylophilus nematodes repeatedly, a small proportion of B. mucronatus genes is infused into the B. xylophilus genome (introgression) and may lead to adaptation to locally harsh environments. Though cool temperatures had inhibited the development of pine wilt disease, B. xylophilus started expanding the range to cool-summer areas after suspending its range expansion for 10 years in Japan. To consider if the range expansion is related to the introgression hybridisation between the two Bursaphelenchus species, some traits of newly and already formed hybrid-derived populations were compared between three temperature conditions of 16, 20 and 25°C. Formation of F1 hybrids was not affected by temperature. There was no difference in the time required for hybrid formation and for population establishment at 16°C between an interspecific crossing and two intraspecific crossings of B. xylophilus. Using three hybrid-derived populations reared over multiple generations at 25°C, there was no difference in the early rate of population growth between each of two hybrid-derived populations and its parental-lineage population of B. xylophilus at 16°C. Thus, the results did not reject a hypothesis that introgression hybridisation may have enhanced the fitness components such as pathogenicity of B. xylophilus populations at cool temperatures.
Summary
Brassica plants naturally produce glucosinolates as secondary metabolites hydrolysed to biocidal isothiocyanates (ITCs). As such, they have the potential for nematode management through a strategy known as biofumigation. Pratylenchus penetrans causes significant yield losses in many important crops. Understanding the relative impact of different ITCs on the motility and mortality of this nematode species could provide some insights into the selection of relevant brassica biofumigants. The effects of 3.125, 6.25, 12.5, 25, and 50 μg ml−1 of pure Allyl, 2-Phenylethyl and Benzyl ITCs on the motility and mortality of P. penetrans were evaluated in laboratory in vitro assays. Motility was assessed after incubating the nematodes in ITCs for 24, 48 and 72 h with distilled water as a negative control. Motile and non-motile nematodes were counted. After motility assessment at 72 h, nematodes were rinsed and incubated in water for 48 h, after which live and dead nematodes were counted. Nematodes were considered dead if they remained non-motile after probing with a picking needle. Nematode motility and mortality were significantly affected by the type of ITC, concentration and time of exposure. The number of non-motile nematodes increased with increasing concentration and time of exposure across all tested ITCs. The ED50 values (concentration required to cause 50% non-motility) of Allyl, 2-Phenylethyl and Benzyl were 37.4, 12.8 and 8.6 μg ml−1 after 24 h exposure. The ITC with potentially the greatest nematicidal effect was Benzyl (LD50 = 3.2 μg ml−1), followed by 2-Phenylethyl (LD50 = 5.2 μg ml−1), and Allyl (LD50 = 9.9 μg ml−1). The LD50 of all ITCs were not different from the ED50 after 72 h, meaning the effects of ITCs could be considered irreversible. This study suggests that brassica biofumigants that produce Benzyl, Allyl and 2-Phenylethyl ITCs are promising candidates for biofumigation of P. penetrans.