Molecular phylogeny, diagnostics, and diversity of plant-parasitic nematodes of the genus Hemicycliophora (Nematoda: Hemicycliophoridae)

The genus Hemicycliophora (Nematoda: Hemicycliophoridae) contains 132 valid species of plant-parasitic nematodes, collectively known as ‘sheath nematodes’. Hemicycliophora spp. are characterized morphologically by a long stylet with rounded basal knobs and a cuticular sheath, present in juvenile and adult stages. Populations of 20 valid and 14 putative species of Hemicycliophora and Loofia from several countries were characterized morphologically using light (LM) and scanning electron microscopy (SEM) and molecularly using the D2-D3 segments of 28S rRNA and internal transcribed spacer (ITS) rRNA gene sequences. LM and SEM observations provided new details on the morphology of these species. PCR-restriction fragment length polymorphisms (PCR-RFLPs) of the D2-D3 of 28S rDNA were proposed for identification of the species. Phylogenetic relationships within populations of 36 species of the genus Hemicycliophora using 102 D2-D3 of 28S rDNA and 97 ITS rRNA gene sequences as inferred from Bayesian analysis are reconstructed and discussed. Ancestral state reconstructions of diagnostic characters (body and stylet length, number of body annuli, shape of vulval lip and tail), using maximum parsimony and Bayesian inference, revealed that none of the traits are individually reliable characters for classifying the studied sheath nematode. The Shimodaira–Hasegawa test rejected the validity of the genus Loofia. This is the most complete phylogenetic analysis of Hemicycliophora species conducted so far.Fil: Subbotin, Sergei A.. California Department of Food and Agriculture; Estados Unidos. Institute of Ecology and Evolution of the Russian Academy of Sciences; RusiaFil: Chitambar, John J.. California Department of Food and Agriculture; Estados UnidosFil: Chizhov, Vladimir N.. Institute of Ecology and Evolution of the Russian Academy of Sciences; RusiaFil: Stanley, Jason D.. Florida Department of Agriculture and Consumer Services; Estados UnidosFil: Inserra, Renato N.. Florida Department of Agriculture and Consumer Services; Estados UnidosFil: Doucet, Marcelo Edmundo. Universidad Nacional de Cordoba. Facultad de Cs.exactas Fisicas y Naturales. Centro de Zoologia Aplicada; Argentina. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Cordoba. Instituto de Diversidad y Ecologia Animal; ArgentinaFil: Mcclure, Michael. University Of Arizona; Estados UnidosFil: Ye, Weimin. North Carolina Department of Agriculture & Consumer Services; Estados UnidosFil: Yeates, George.Fil: Mollov, Dimitre S.. University Of Minnesota; Estados UnidosFil: Cantalapiedra Navarrete, Carolina. Consejo Superior de Investigaciones Científicas. Instituto de Agricultura Sostenible; EspañaFil: Vovlas, Nicola. Istituto per la Protezione delle Piante; ItaliaFil: Van Den Berg, Esther. ARC-Plant Protection Research Institute; SudáfricaFil: Castillo, Pablo. Consejo Superior de Investigaciones Científicas. Instituto de Agricultura Sostenible; Españ

Genetic Structure of Xiphinema pachtaicum

The dagger nematodes Xiphinema pachtaicum and X. index are two of the most widespread and frequently occurring Xiphinema spp. co-infesting vineyards and other crops and natural habitats worldwide. Sexual reproduction is rare in these species. The primary objective of this study was to determine the genetic structure of X. pachtaicum and X. index populations using eight and seven populations, respectively, from different "wine of denomination of origin (D.O.) zones" in Spain and Sardinia (Italy), by studying mitochondria! (cytochrome oxidase c subunit 1 or COI) and nuclear (D2-D3 expansion segments of 28S rDNA) markers. Both Xiphinema spp. showed low intraspecific divergence among COI sequences, ranging from 0.2% (1 base substitution) to 2.3% (10 substitutions) in X. pachtaicum and from 0.2% (I base substitution) to 0.4% (2 substitutions) in X. index. Population genetic structure was strong for both species. Nevertheless, molecular differences among grapevine-growing areas were not significant, and intrapopulation diversity was very low. It is hypothesized that this genetic homogeneity in the nematode populations reflects their predominant parthenogenetic reproduction mode and low dispersal abilities. Our results also show that X. pachtaicum populations in Spain have possibly been established from two different populations of origin. Results also demonstrated that the two DNA regions studied are suitable diagnostic markers for X. index and X. pachtaicum

Unravelling the Biodiversity and Molecular Phylogeny of Needle Nematodes of the Genus Longidorus (Nematoda: Longidoridae) in Olive and a Description of Six New Species

The genus Longidorus includes a remarkable group of invertebrate animals of the phylum Nematoda comprising polyphagous root-ectoparasites of numerous plants including several agricultural crops and trees. Damage is caused by direct feeding on root cells as well as by transmitting nepoviruses that cause disease on those crops. Thus, correct identification of Longidorus species is essential to establish appropriate control measures. We provide the first detailed information on the diversity and distribution of Longidorus species infesting wild and cultivated olive soils in a wide-region in southern Spain that included 159 locations from which 449 sampling sites were analyzed. The present study doubles the known biodiversity of Longidorus species identified in olives by including six new species (Longidorus indalus sp. nov., Longidorus macrodorus sp. nov., Longidorus onubensis sp. nov., Longidorus silvestris sp. nov., Longidorus vallensis sp. nov., and Longidorus wicuolea sp. nov.), two new records for wild and cultivate olives (L. alvegus and L. vineacola), and two additional new records for wild olive (L. intermedius and L. lusitanicus). We also found evidence of some geographic species associations to western (viz. L. alvegus, L. intermedius, L. lusitanicus, L. onubensis sp. nov., L. vineacola, L. vinearum, L. wicuolea sp. nov.) and eastern distributions (viz. L. indalus sp. nov.), while only L. magnus was detected in both areas. We developed a comparative study by considering morphological and morphometrical features together with molecular data from nuclear ribosomal RNA genes (D2–D3 expansion segments of 28S, ITS1, and partial 18S). Results of molecular and phylogenetic analyses confirmed the morphological hypotheses and allowed the delimitation and discrimination of six new species of the genus described herein and four known species. Phylogenetic analyses of Longidorus spp. based on three molecular markers resulted in a general consensus of these species groups, since lineages were maintained for the majority of species. This study represents the most complete phylogenetic analysis for Longidorus species to date.Financial support was received by Projects AGL-2012-37521 from ‘Ministerio de Economía y Competitividad’ of Spain, Project P12-AGR-1486 from ‘Consejería de Economía, Innovación y Ciencia’ of Junta de Andalucía, and FEDER financial support from the European Union is gratefully acknowledged. The grant 219262 ArimNET_ERANET FP7 2012–2015 Project PESTOLIVE ‘Contribution of olive history for the management of soilborne parasites in the Mediterranean basin’ from Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA), also provided partial financial support.Peer reviewe