Journal of nematology最新文献

Crape myrtle (Lagerstroemia indica), a popular ornamental tree in the southern United States, was observed with severe root galls in a commercial nursery in central Alabama. Soil samples yielded high populations of root-knot nematode juveniles (104-277 J2/100 cm³). Morphology and morphometrics were consistent with Meloidogyne spp., but species-specific PCR for M. incognita, M. arenaria, M. javanica, and M. hapla were all negative. Sequencing of 18S, 28S rDNA, and mitochondrial COII-16S rRNA regions showed >99.5% identity to M. enterolobii. Two M. enterolobii-specific primers confirmed the diagnosis. A clonal population was maintained on tomatoes and used in a host range and pathogenicity assay. High reproduction (reproduction factor ≥8.6) occurred on pepper, sweet potato, tomato, and watermelon, while limited reproduction was found on peanut, corn, and one cotton cultivar. This is the first report of M. enterolobii infecting a commercial plant in Alabama. Due to its aggressive nature, wide host range, and ability to overcome resistance, there is an urgent need for monitoring and management strategies against this species.

The reniform nematode (Rotylenchulus reniformis) is one of the most problematic nematodes affecting soybean (Glycine max (L.) Merrill) in Louisiana. Although reniform nematode-resistant soybean varieties have been identified in previous studies, the response of soybean varieties grown in Louisiana remains unclear. This study evaluated reniform nematode population development and yield using a series of field trials. It focused on commonly planted soybean varieties, as well as University of Missouri varieties with reported resistance to the reniform nematode. Field trials were conducted in 2022 and 2023 at two locations in Louisiana. The resistant soybean varieties consistently suppressed reniform nematode soil population densities, achieving population reductions of 73% in 2022 and 72% in 2023, relative to the commercially planted soybean varieties. Resistant soybean varieties generally achieved higher yields than the commercial soybean varieties. This trend was consistent across the field trials conducted over both years. Overall, this study has demonstrated that resistant soybean varieties can be an effective tool in reducing reniform nematode populations in infested fields and often achieve higher yields compared to the currently grown soybean varieties in Louisiana.

Globodera pallida, the pale cyst nematode is a regulated pest in Idaho. This study investigated whether rotation of the trap crop Solanum sisymbriifolium and a resistant potato variety was effective for controlling G. pallida in Idaho. The highly resistant potato variety, 'Innovator', was used. Three-year crop rotations incorporating 'Innovator' and S. sisymbriifolium before a susceptible potato were established in an Idaho field. At the end of each growing season, the impact of each crop on the initial population used to infest soil and progeny cysts was evaluated. 'Innovator' and S. sisymbriifolium similarly reduced encysted eggs of the initial population by 70% after the first year. However, S. sisymbriifolium further reduced egg viability of the initial population to 58%, compared with 'Innovator' plots with 89% egg viability. By the end of year 3, reproduction factors (RF; final egg population/initial egg population) showed that all rotations resulted in 99%-100% overall reduction in the initial G. pallida population density. After 2 years of S. sisymbriifolium, cysts were undetectable following the susceptible potato 'Russet Burbank'. These results demonstrate the potential of S. sisymbriifolium and resistant potato in rotation to reduce G. pallida population densities.

Radopholus similis severely damages banana roots causing significant yield losses. Field screening for resistance is labor intensive and inconsistent due to environmental variation and mixed nematode populations. The screenhouse offers a controlled environment but is limited by the time needed for root development and variation in plant growth. We developed and validated a high-throughput in vitro method for phenotyping banana resistance to R. similis using sand-Murashige and Skoog (MS) media. Tissue culture plantlets grown in sterilized sand-MS were inoculated with 50 female R. similis after root development and nematodes extracted eight weeks after inoculation to calculate the reproduction factor (RF). Although RF values were higher for in vitro than in the screenhouse, accession responses showed similar trends under both conditions. The in vitro method was rapid, cost-effective with higher throughput, accelerating phenotyping and enabling rapid assessment of banana accessions for breeding programs. Some accessions responded differently to the two methods indicating that additional methods, such as root necrosis scores are important to confirm resistance. This study is the first in vitro-based demonstration of phenotyping for nematode resistance using modified sand-MS media with improved root development and pathogen interactions.

The Pacific shoot-gall nematode (Anguina pacificae) is an economically important pest of annual bluegrass (Poa annua L.) putting greens in the coastal areas of northern and central California. In December 2024, diagnostic samples submitted to the Oregon State University Turfgrass Diagnostic Clinic (Corvallis, OR) from a golf course tee box in Clark County, Washington contained A. pacificae. Visual symptoms of chlorotic patches and dieback of the turf surface were observed, as well as swellings in the crowns that contained second-stage juveniles (J2). Morphological features as well as morphometric measurements of J2 were consistent with A. pacificae. Sequencing of the internal transcribed spacer (ITS) and the mitochondrially encoded cytochrome c oxidase I (COX1) gene regions confirmed the species identity. To our knowledge, this is the first report of A. pacificae parasitizing turfgrass in Washington.

Plant-parasitic nematodes are responsible for substantial yield losses in banana-growing regions worldwide. In Türkiye, banana is traditionally grown in limited open-field areas, but greenhouse cultivation has rapidly expanded in recent years. However, information on nematodes associated with greenhouse bananas is extremely limited. This study aimed to determine the occurrence, races, and population densities of economically important nematodes in banana greenhouses. Surveys conducted between 2021-2022 in both new and old banana-producing regions revealed the presence of Rotylenchulus reniformis and Meloidogyne incognita in greenhouses in Mersin. R. reniformis was identified as race 2, while M. incognita was race 1. The population density of M. incognita increased when soil temperature rose above 10 °C, and R. reniformis densities increased above 20 °C. M. incognita was dominant during 2021-2022; however, its population was significantly suppressed by R. reniformis in 2022-2023.

Brassica carinata (carinata) is an emerging winter biofuel crop in the southeastern United States. Rotylenchulus reniformis (reniform nematode) is an important yield-robbing parasite on cotton in the region. A better understanding of rotation systems involving carinata would guide R. reniformis management and crop selection decisions. This study aimed to determine the effect of winter crop rotations with or without carinata, in combination with summer crops, on R. reniformis at two soil depths in a field study in North Florida. Two-year winter rotations included fallow-carinata, fallow-fallow, and oat-carinata. Winter rotations were crossed with corn, cotton, soybean, and peanut each year. Soil samples were taken from 0-30 cm and 30-120 cm depth after both summer and winter crop harvest for 4 yr. Rotylenchulus reniformis soil abundances were greater at 0-30 cm than at 30-120 cm deep, but crop effects were generally similar at both depths. Cotton supported greater R. reniformis soil abundances than corn, peanut, or soybean. Winter rotations did not consistently affect R. reniformis, regardless of prior summer crop, although carinata tended to decrease R. reniformis soil abundances. In summary, carinata production expands options for winter crop rotations to manage R. reniformis.

During a survey of the nematode biodiversity in the Petrel wetland (central Chile), a population of Heterorhabditis sp. was found in the coastal dune samples. Morphological, morphometric, and molecular studies indicated that this nematode belonged to the megidis group, and represented a novel species, which we named Heterorhabditis caligo n. sp. This nematode species resembles H. marelatus but it is different in the morphometrics of its infective juvenile in the following ways: pharynx length (135-150 μm vs. 120-138 μm), and the position of the excretory pore from the anterior end (105-128 μm vs. 81-113 μm). In males, the fourth and eighth pairs of the bursal papillae are shorter and do not reach the edge of the bursa in H. caligo n. sp., whereas all the papillae in H. marelatus reach the edge of the bursa. The excretory pore of amphimictic females of H. caligo n. sp. is located more posteriorly than in those of H. marelatus 193 (169-224) μm vs. 157 (139-178) μm, respectively. Phylogenetic analyses of the genus based on whole nuclear and mitochondrial genome sequences and on five gene markers showed a clear separation of Heterorhabditis caligo n. sp. from the other species, placing it within the megidis group.

A new species of free-living nematode inhabiting microbialites in Great Salt Lake, Utah, USA is described both molecularly by 18S-sequencing and morphologically with scanning electron microscopy and differential interference contrast (DIC) microscopy. Diplolaimelloides woaabi sp. nov. (family Monhysteridae, order Monhysterida) is characterized by a combination of the following characters: ocelli present; a relatively small body size (<1.5 mm); short anterior sensory setae; cryptospiral amphidial fovea; a funnel-shaped anterior buccal cavity and reduced secondary cavity; fused lips; long double spicules and conspicuous male bursa displaying four pairs of post-cloacal papillae arranged in a (2 + 2) pattern, a single mid-ventral pre-cloacal papilla, two pairs of papillae posterior to the bursa, and an additional offset mid-tail papillae pair; and a pair of sub-apical extensions on spicules. An updated key to all species of Diplolaimelloides Meyl, 1954 is given. This species is notable for its adaptation to hypersaline microbialites, positioning it as both an extremophile and a potential bioindicator of ecological change in Great Salt Lake.