Characterisation of populations of Longidorus orientalis Loof, 1982 (Nematoda: Dorylaimida) from date palm (Phoenix dactylifera L.) in the USA and other countries and incongruence of phylogenies inferred from ITS1 rRNA and coxI genes

Abstract

Needle nematode populations ofLongidorus orientalisassociated with date palm,Phoenix dactylifera, and detected during nematode surveys conducted in Arizona, California and Florida, USA, were characterised morphologically and molecularly. The nematode species most likely arrived in California a century ago with propagative date palms from the Middle East and eventually spread to Florida on ornamental date palms that were shipped from Arizona and California. This is the first validated continental record of this needle nematode species in the USA and the Americas. The USA populations ofL. orientaliscontained a small number of males that were not reported in the original description and are herein described.Longidorus orientaliswas able to survive for at least 4 years at very low numbers in the warm and humid environment of Florida on date palms imported from California and Arizona. Association ofL. orientaliswithL. africanuswas observed in all of the surveyed sites, indicating that date palm is a host of both nematodes. Phylogenetic relationships ofL. orientaliswith closely relatedLongidorusspecies, in addition to relationships between populations ofL. orientalisfrom the USA, Greece, Iran and Spain, were inferred from the analyses of D2-D3 of 28S rRNA, ITS1 rRNA and partialcoxIgene sequences. The PCR-D2-D3 expansion segments of 28S rDNA-RFLP diagnostic profile is provided.Longidorus orientalispopulations display a high level of intraspecific variation (up to 15.5%) incoxImtDNA sequences. Analysis of phylogenetic relationships of nematode populations revealed incongruence of the ITS1 rRNA andcoxImtDNA gene trees, which might be the result of selective introgression of mtDNA through gene flow between previously isolated populations introduced simultaneously into new geographical regions.

MORPHOLOGICAL AND GENETIC CHARACTERIZATION OF NEMATODES OF THE OPOSSUM Didelphis albiventris AND THE ARMADILLO Dasypus novemcinctus FROM SERRA DA CAPIVARA NATIONAL PARK

“…The mitochondrial cox-1 gene has been initially proposed as a standard reliable genetic marker to elucidate cryptic, diversity and barcode eukaryote species (Subbotin et al 2015). Studies using cox1 as genetic marker for nematodes have displayed a low level of intraspecific variation and higher level interspecificity, but there are exceptions (Blouin 2002).…”

“…The high dissimilarity level could have occurred due to isolation of the parasite population in SCNP, in addition to evolutionary processes undergone by parasites in different hosts. The data on cox-1 could also cast doubt on the reliability of Nematoda DNA barcoding, which can adversely affect the accuracy of Nematoda identification as discussed by Gutiérrez-Gutiérrez et al (2013) and Subbotin et al (2015). The same process could have occurred with the 16S rRNA gene for A. raillieti from D. albiventris and A. vazi from D. novemcinctus from Brazil.…”

Molecular phylogenetic analysis and comparative morphology reveals the diversity and distribution of needle nematodes of the genus Longidorus (Dorylaimida: Longidoridae) from Spain

“…from GenBank were used for phylogenetic reconstruction. Outgroup taxa for each dataset were chosen based on previous published studies (He et al, 2005;Holterman et al, 2006;Gutiérrez-Gutiérrez et al, 2013;Subbotin et al, 2015;Archidona-Yuste et al, 2016a;Xu et al, 2017). Multiple sequence alignments of the different genes were made using the Q-INS-i algorithm of MAFFT v. 7.205 (Katoh & Standley, 2013) which accounts for secondary RNA structure.…”

“…Accurate identification of needle nematodes is essential to establish an unequivocal diagnosis to discriminate virus vector species, select appropriate management strategies for preventing their spread and establish efficient control measures. Recent studies using an integrative approach for identification highlighted the difficulty of correct identification at the species level within the genus Longidorus, as well as cryptic species separation (Subbotin et al, 2015; Archidona-Yuste et al, 2016a; Peraza-Padilla et al, 2017; Xu et al, 2017Xu et al, , 2018. These studies provide molecular markers based on ribosomal RNA (rRNA) (D2-D3 expansion domains of 28S rRNA, ITS and 18S rRNA) and mitochondrial DNA (mtDNA) genes (cytochrome c oxidase subunit I or CoxI) for precise and unequivocal diagnoses of some species of Longidorus, demonstrating that this genus is a complex and taxonomically important group of plantparasitic nematodes.…”

DNA barcoding, phylogeny and phylogeography of the cyst nematode species of the Avenae group from the genus Heterodera (Tylenchida: Heteroderidae)

“…Although, we consider our results with mitochondrial marker indicative, it should be taken into account that a single marker may not accurately reflect species history. In fact, we cannot completely exclude the possibility of asymmetrical introgression of mitochondrial DNA between some populations, a phenomenon that may be observed in some nematode species (Subbotin et al, 2015).…”