Symptoms of beech leaf disease (BLD), first reported in Ohio in 2012, include interveinal greening, thickening and often chlorosis in leaves, canopy thinning and mortality. Nematodes from diseased leaves of American beech (Fagus grandifolia) sent by the Ohio Department of Agriculture to the USDA, Beltsville, MD in autumn 2017were identified as the first recorded North American population of Litylenchus crenatae (Nematology, 21, 2019, 5), originally described from Japan. This and other populations from Ohio, Pennsylvania and the neighbouring province of Ontario, Canada showed some differences in morphometric averages among females compared to the Japanese population. Ribosomal DNA marker sequences were nearly identical to the population from Japan. A sequence for the COI marker was also generated, although it was not available from the Japanese population. The nematode was not encountered in Fagus crenata (its host in Japan) living among nematode-infested Fagus grandifolia in the Holden Arboretum, nor has L. crenatae been reported in American beech in Japan. The morphological and host range differences in North American populations are nomenclaturally distinguished as L. crenatae mccannii ssp. n. from the population in Japan. Low-temperature scanning electron microscopy (LT-SEM) demonstrated five lip annules and a highly flexible cuticle. Females, juveniles and eggs were imaged within buds with a Hirox Digital microscope and an LT-SEM. Nematodes swarmed to the tips of freshly cut beech buds, but explants could not be maintained. Inoculation of fresh nematodes from infested leaves or buds to buds or leaves ofF. grandifolia seedlings resulted in BLD leaf symptoms. Injuring dormant buds prior to nematode application, in fall or spring, promoted the most reliable symptom expression. The biogeography and physiology of anguinid nematode leaf galling, and potential co-factors and transmission are discussed. K E Y W O R D S Anguinidae, digital and scanning electron microscopy, foliar nematode, host range, molecular identification, morphometrics, new continent detection, new subspecies, symptom transmission, taxonomy 2 of 15 | CARTA eT Al.

Plant-parasitic nematodes (PPNs) are important pests that cause an estimated ten billion dollars of crop loss each year in the United States and over 100 billion dollars globally. The Animal and Plant Health Inspection Service (APHIS) within the U.S. Department of Agriculture maintains and updates the U.S. Regulated Plant Pest list. Currently, the number of PPNs regulated by APHIS includes more than 60 different species. This review focuses on the top ten most economically important regulated and emerging plant-parasitic nematodes and summarizes the diagnostics of morphological and some molecular features for distinguishing them. These ten major previously described nematode species are associated with various economically important crops from around the world. This review also includes their current distribution in the U.S. and a brief historical background and updated systematic position of these species. The species included in this review include three PPNs considered by the U.S. Department of Agriculture as invasive invertebrates Globodera pallida, Globodera rostochiensis, and Heterodera glycines; four regulated PPNs, namely Bursaphelenchus xylophilus, Meloidogyne fallax, Ditylenchus dipsaci, and Pratylenchus fallax; and the three emerging PPNs Meloidogyne chitwoodi, Meloidogyne enterolobii, and Litylenchus crenatae mccannii.

Root-lesion nematodes (Pratylenchus spp.) of the genus Pratylenchus Filipjev, 1936, are among the most important nematode pests on soybean (Glycine max (L.) Merr.), along with soybean cyst and root-knot nematodes. In May 2015 and 2016, a total of six soil samples were collected from a soybean field in Walcott, Richland County, ND and submitted to the Mycology and Nematology Genetic Diversity and Biology Laboratory (MNGDBL), USDA, ARS, MD for analysis. Later, in 2019, additional nematodes recovered from a greenhouse culture on soybean originally from the same field were submitted for further analysis. Males, females, and juveniles of Pratylenchus sp. were recovered from soil and root samples and were examined morphologically and molecularly. DNA from single nematodes were extracted, and the nucleotides feature of three genomic regions targeting on the D2–D3 region of 28S rDNA and ITS rDNA and mitochondrial cytochrome oxidase subunit I (COX1) gene were characterized. Phylogeny trees were constructed to ascertain the relationships with other Pratylenchus spp., and polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was performed to provide a rapid and reliable differentiation from other common Pratylenchus spp. Molecular features indicated that it is a new, unnamed Pratylenchus sp. that is different from morphologically closely related Pratylenchus spp., including P. convallariae, P. pratensis, P. fallax, and P. flakkensis. In conclusion, both morphological and molecular observations indicate that the North Dakota isolate on soybean represents a new root-lesion nematode species which is named and described herein as Pratylenchus dakotaensis n. sp.

In the summer of 2016, a field of corn (Zea mays) in Spencer County, Indiana was observed with heavily stunted plants, and from the affected roots a large number of cysts were recovered. Soil samples were submitted to one of us (JF), who extracted the nematode cysts and sent them to the USDA-ARS, Mycology and Nematology Genetic Diversity and Biology Laboratory (MNGDBL), Beltsville, MD for morphological and molecular identification. Cysts and the recovered second-stage juveniles (J2) that were examined morphologically conformed to the measurements of Vittatidera zeaphila, the goose cyst nematode originally described from Tennessee, USA in 2010. The molecular analysis of J2 showed the sample from Spencer County matched exactly with V. zeaphila according to ribosomal DNA markers ITS, 28S, and 18S, and with mitochondrial cytochrome oxidase I (COI). The nuclear marker heat shock protein 90 (Hsp90) was also analyzed for the first time from the Indiana population of V. zeaphila. Similarities to existing cyst nematode sequences are reported herein. Geographically, although the county is across the Ohio River from Kentucky, the previously reported Hickman County, Kentucky location and Indiana detection are approximately 200 miles apart. To the best of our knowledge, this is the first report of V. zeaphila in Indiana.

Citrullus amarus (CA) (previously known as Citrullus lanatus var. citroides) accessions collected in southern Africa are known to have resistance to root-knot nematodes (RKN) and are suitable rootstocks for grafted watermelon. The objective of this study was to conduct a comparative metabolomics analysis and identify unique metabolites in roots of CA accessions versus roots of watermelon cultivars (Citrullus lanatus (Thunb.) Matsum. and Nakai var. lanatus; CL). Nuclear magnetic resonance (NMR) technology and principal component analysis (PCA) were used to analyze and compare metabolic profiles of seven CA accessions resistant to RKN along with two RKNsusceptible watermelon cultivars (Charleston Gray and Crimson Sweet). Calculation of the Mahalanobis distance revealed that the CA United States Plant Introduction (PI) 189225 (Line number 1832) and PI 482324 (1849) have the most distinct metabolic profiles compared with the watermelon cultivars Charleston Gray and Crimson Sweet, respectively. Several amino acids identified in the CA accessions were reported in previous studies to have a nematicidal effect. The results in this study indicate that roots of watermelon accessions collected in the wild are rich in metabolic compounds. These metabolic compounds may have been diminished in watermelon cultivars as a consequence of many years of cultivation and selection for desirable fruit qualities.