Molecular Characterization of an Emerging Root-Knot Nematode Meloidogyne enterolobii in North Carolina, USA

Abstract

An emerging threat to agriculture, Meloidogyne enterolobii Yang & Eisenback, 1983 is a tropical species and considered to be the most damaging root-knot nematode (RKN) in the world because of its wide host range, aggressiveness, and ability to overcome resistance to RKN in many crops. It was first detected in the USA on ornamental plants in Florida in 2001, but has since been identified in North Carolina, South Carolina and Louisiana. Several thousand RKN populations were collected from North Carolina field crops, ornamental plants and turfgrasses for species identification in the Nematode Assay Laboratory in the North Carolina Department of Agriculture & Consumer Services (NCDA&CS). From 2006 to 2019, root systems showing galling symptoms were dissected under the microscope and females were obtained for DNA analysis. When only soil samples were submitted, the second-stage juveniles or males were used instead. Molecular characterization was performed by PCR using species-specific primers and DNA sequencing on the ribosomal DNA 18S-ITS1-5.8S and 28S D2/D3, and mitochondrial DNA CoxII-16S. One hundred and thirty-five representative RKN populations from North Carolina were characterized and identified as M. enterolobii. Six populations from China where the species was originally described were included in this study for identity confirmation and comparison. As of December 2019, M. enterolobii was confirmed from a limited number of fields in 11 North Carolina counties, including Columbus, Craven, Greene, Harnett, Johnston, Lenoir, Nash, Pitt, Sampson, Wayne and Wilson. Currently, M. enterolobii is the most important emerging RKN species in the USA and causes severe damage to agronomic and horticultural crops, especially sweetpotato in North Carolina.

Molecular phylogeny and morphological studies reveal a 30‐year‐old rain tree (Samanea saman) maintains populations of Meloidogyne enterolobii, a new host plant in Thailand

“…On the other hand, the phylogenetic analysis of two M. enterolobii from rain tree and chilli compared to several studies indicates that it has a low level of nucleotide variation, indicating a lack of genetic diversity among M. enterolobii populations that results in having the sequences distinctly different from those of all other known RKN species (Onkendi & Moleleki, 2013; Shao et al, 2020; Ye et al, 2019). Similar results were reported by Ye et al (2021), who found a low nucleotide substitution site in M. enterolobii based on the quality of Sanger DNA sequencing. As such, there should be an extensive analysis to obtain a contig file based on multiple forward and reverse sequences and an evaluation of nucleotide position peaks and protein translation peaks.…”

“…TA B L E 3Both genes are highly conserved in M. incognita and the closely related to RKN, as demonstrated by blast search(Ye et al, 2019), which can detect multiple homologous species from the similarity in sequence and species complexes based on phylogenetic trees.Multiple analyses suggest a polyphyletic clade of M. incognita with similar sequence traits known as homoplasy, which explained by convergent evolution.that it has a low level of nucleotide variation, indicating a lack of genetic diversity among M. enterolobii populations that results in having the sequences distinctly different from those of all other known RKN species(Onkendi & Moleleki, 2013;Shao et al, 2020;Ye et al, 2019). Similar results were reported byYe et al (2021), who found a low nucleotide substitution site in M. enterolobii…”

“…The phylogenetic tree files were graphically displayed in FigTree (http://tree.bio.ed.ac.uk/softw are/figtree). For each data set, the outgroup taxa were chosen based on the results from previous studies (Álvarez-Ortega et al, 2019;Ye et al, 2019Ye et al, , 2021.…”

Non-fumigant Nematicides are Promising Alternatives to Fumigants for the Management of Meloidogyne enterolobii in Tobacco

“…As seen with many other agricultural crops, M. enterolobii management in tobacco is challenging. A very wide host range and ability to overcome resistance effective for other common species of root-knot nematodes make M. enterolobii unmanageable with currently available nematode management practices ( Brito et al ., 2007 ; Kiewnick et al ., 2009 ; Rutter et al ., 2019 ; Ye et al ., 2021 ; Khanal and Harshman, 2022 ). The use of fumigant nematicides is the most common method of nematode management in commercial agricultural production systems; however, none of the currently available fumigants are able to provide satisfactory management of M. enterolobii .…”

Parental choice and seed size impact the uprightness of progeny from interspecific Glycine hybridizations

“…However, drought tolerance has been identified in soybean curated in the United States Department of Agriculture (USDA) germplasm collection (Kunert & Vorster, 2020; Sloane et al., 1990). As another example, the guava root knot nematode ( Meloidogyne enterolobii ) has emerged as a pest in soybean, but no resistance has been detected in US cultivars (Wilson, 2018; Ye et al., 2021). Additionally, the seed protein content of many high‐yielding US commercial soybean cultivars released prior to 2017 is 38%–42% protein (dry weight) and is inadequate to meet the demand for meal with >47.5% protein (de Borja Reis et al., 2020; Patil et al., 2017).…”