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The genus Paratrichodorus currently comprises 26 species of polyphagous ectoparasitic plant nematodes that are distributed worldwide and include a few tobravirus vector species. Paratrichodorus is one of the most difficult genera for species identification because it is phenotypically conserved, with morphometric characters that often overlap between species. From 2003 to 2016, nematode surveys were conducted in southern Spain, and the present study addresses 22 nematode populations of the Paratrichodorus hispanus group. Among them, two new species, Paratrichodorus almadenensis sp. nov. and Paratrichodorus ramblensis sp. nov. are described here morphologically and molecularly and compared with topotype specimens of Paratrichodorus hispanus. Furthermore, this analysis was complemented with the first molecular data for this species complex and for the genus Monotrichodorus. The phylogeny of family Trichodoridae showed the relationship of Monotrichodorus with Trichodorus, both of which are phylogenetically associated with the P. hispanus species group, including the two newly described species. Several phylogenetic hypotheses about the monophyly of the genera with molecular data composing the family Trichodoridae were tested using Shimodaira–Hasegawa and approximately unbiased tests. This work also includes the first observations of copulatory plugs in Paratrichodorus, which clearly differ from the different types of mating plugs described in Trichodorus species. [ABSTRACT FROM AUTHOR]

This work has studied for the first time the structure and diversity of plant-parasitic nematodes (PPNs) infesting olive orchard soils in a wide-region in Spain that included 92 locations. It aims at determining which agronomical or environmental factors associated to the olive orchards are the main drivers of the PPNs community structure and diversity. Classical morphological and morphometric identification methods were used to determine the frequency and densities of PPNs. Thirteen families, 34 genera and 77 species of PPNs were identified. The highest diversity was found in Helicotylenchus genus, with six species previously reported in Spain and with H. oleae being a first report. Neodolichorhynchus microphasmis and Diptenchus sp., Diphtherophora sp., and Discotylenchus sp., usually considered fungal feeders, were also reported for the first time associated to olive rhizosphere. PPNs abundance ranged from 66 to 16,288 individuals/500-cm3 of soil with Helicotylenchus digonicus being the most prevalent species, followed by Filenchus sp., Merlinius brevidens and Xiphinema pachtaicum. Nematode abundance and diversity indexes were influenced by olive cultivar, and orchard and soil management practices; while olive variety and soil texture were the main factors driving PPN community composition. Soil physicochemical properties and climatic characteristics most strongly associated to the PPN community composition included pH, sand content and exchangeable K, and maximum and minimum average temperature of the sampled locations. Our data suggests that there is a high diversity of PPNs associated to olive in Southern Spain that can exert different damage to olive roots depending on the olive variety and their abundance. Further analysis to determine the resistance levels of most common olive varieties to the prevalent PPNs in Spain will help to choose the most appropriate ones for the establishment of new plantations. This choice will take into consideration the specific soils and environments where those olive varieties will be established. [ABSTRACT FROM AUTHOR]

Abstract: The nematode Rotylenchus paravitis n. sp. infesting roots of commercial sunflowers in southern Spain is described. The new species is characterised by a truncate lip region with 7–9 annuli and continuous with the body contour, lateral fields areolated at pharyngeal region only, body without longitudinal striations, stylet length of 44–50μm, vulva position at 43–54%, tail rounded to hemispherical with 12–18 annuli. A comparative phenetic study based on a multivariate principal component analysis was developed to determine potential species discrimination. The degree of variation for most characters among specimens of Rotylenchus paravitis n. sp. and R. vitis was comparable to that observed among specimens belonging to each of the two studied populations of R. robustus from Spain and USA. Molecular comparison of the partial 18S, D2-D3 expansion segments of 28S-rRNA, ITS1-rRNA, partial COI and hsp90 from R. paravitis n. sp. and R. vitis, and other species in the genus, clearly supports the proposal of R. paravitis n. sp. as a new species. Consequently, R. paravitis n. sp. should be considered as an example of cryptic speciation within the genus Rotylenchus. PCR-ITS-RFLP was provided for diagnostics of R. paravitis n. sp. and PCR with specific primers were also developed for diagnostics of this new species, R. vitis and R. robustus. The results of the phylogenetic analysis based on the sequences of the D2-D3 expansion regions of the 28S, ITS1-rRNA genes, and the partial COI, have proven to be a powerful tool for providing accurate species identification and assessing phylogenetic relationships within the genus Rotylenchus. Phylogenetic testing of D2-D3 expansion segments of 28S-rRNA gene sequences did not refute the monophyly of the genera Rotylenchus, Helicotylenchus, Hoplolaimus, based on tree topologies and the Shimodaira–Hasegawa test even with the split in several clades for some of the genera. [Copyright &y& Elsevier]

Abstract: Classical and molecular methods were used to study the nematode communities associated with rhizosphere soil and roots of a collection of 16 olive cultivars from a world olive germplasm bank in Mengibar (Jaen province, southern Spain). Classical nematological analysis, including soil nematode extraction, species counting and morphological identification showed that 24 taxa belonging to 9 genera (including Aphelenchoides, Criconemoides, Ditylenchus, Filenchus, Helicotylenchus, Merlinius, Paratylenchus, Tylenchus, and Xiphinema) and 8 families (including Anguinidae, Aphelenchidae, Belonolaimidae, Criconematidae, Hoplolaimidae, Longidoridae, Tylenchidae and Tylenchulidae) of plant-parasitic nematodes were present, with one species (Helicotylenchus digonicus) being prevalent in all samples. The low values of the plant-parasitic nematode index (PPI) indicated a high disturbance of the field soil probably due to application of herbicides and fertilizers. Cluster analysis of population densities of the various nematode species, nematode trophic groups, and ecological indices grouped most olive cultivars into three main clusters indicating that olive genotypes differ in the nematode communities in their rhizosphere soil. The use of T-RFLP analysis discriminated to a higher extent the nematode communities present in the rhizosphere soil from the different olive cultivars as compared to the morphological-based analysis. This study provides the first evidence of an effect of the olive genotype on nematode community composition by combining classical morphological and molecular approaches. [Copyright &y& Elsevier]