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

Integrative diagnosis of root-lesion nematodes of the genus Pratylenchus

Ponencia presentada en el XLIII ONTA Annual Meeting, celebrado en Coimbra (Portugal/ del 4 al 9 de septiembre de 2011. Organización de Nematólogos de los Trópicos Americanos (ONTA)Root-lesion nematodes of the genus Pratylenchus are migratory endoparasites that are distributed worldwide and are regarded as severe constraints of many crops. Proper identification of these nematodes (> 70 species) is critical for their management and phytosanitary purposes. The morphological separation of Pratylenchus species is complicated due to their high morphological plasticity, the small number of the differential characters available and high intraspecific variability of some of these characters. During the last decades, new approaches based on biochemical, molecular and phylogenetic analyses have provided powerful tools to nematode systematics and reliable identification of Pratylenchus spp. In particular the ITS, 18S and 28S ribosomal regions have been largely used to discriminate among different populations and species of Pratylenchus. The need for applying a polyphasic approach to characterize Pratylenchus species, and, in addition, to demonstrate the existence of cryptic or complex species, which are morphologically indistinguishable but genetically divergent, has been shown in recent morphological and molecular studies of members of this genus. The findings of these studies, conducted in the last decade, have produced a great number of new sequences and taxa used for testing hypotheses of phylogenetic relationships within Pratylenchus and have emphasized the importance of polyphasic taxonomy as a better strategy to delimit species and to infer phylogenetic relationships in this complex group of nematodes.Peer Reviewe

First Report of Direct Damage Caused by the Stubby-Root Nematode, Nanidorus minor, to Strawberry (Fragaria x ananassa), in Florida

In 2019–2022, declining symptoms were observed in two commercial strawberry farms in Hillsborough County, Florida. The fields in the two farms consisted of raised beds covered by plastic mulch. Both were fumigated with a mixture of 1,3-dichloropropene (40%) + chloropicrin (60%) before planting. Samples collected from large patches with declining plants were infested with stubby-root nematodes. No sting and root-knot nematode species were detected. The results of morphological and molecular analyses indicated that the stubby-root nematode populations were representative of the species Nanidorus minor. The two cultivars ‘Florida Brilliance’ and ‘Florida Sensation’ in the two fields included plants with stubby root symptoms showing a reduction in the size of the root system and arrested growth and elongation of the feeder roots on the first strawberry crop. The nematode population densities in the two fields increased at the end of strawberry season and averaged 66 and 96 specimens in 200 cm3 soil. In one of the fields, a second strawberry crop was established as in the previous year using the same practices (fumigation and raised beds covered with plastic). However, in this field the population of N. minor declined and did not reach damaging levels at the end of the season on the second strawberry crop. The factors causing the decline of the nematode population were not elucidated. This is the first report of a direct damaging effect of N. minor to strawberry

Pratylenchidae – the lesion nematodes

Peer reviewe

Characterisation of a topotype and other populations of Hemicriconemoides strictathecatus Esser, 1960 (Nematoda: Criconematidae) from Florida with description of H. phoenicis sp. n. from the USA

The results of morphological and molecular analyses of a Florida topotype and other populations of Hemicriconemoides strictathecatus showed that this sheathoid nematode consists of two morphotypes, both with an average stylet length of more than 70 μm, but having different tail termini, bluntly pointed or rounded. These findings confirmed the morphological similarity of H. strictathecatus with H. mangiferae, which was considered a junior synonym of this species as previously proposed by Decraemer & Geraert (1992, 1996). Populations of a sheathoid nematode with a stylet length ranging from 62.5 to 72.0 μm from Taiwan, China, South Africa and Venezuela and identified in previous studies as H. strictathecatus were found to be morphologically and molecularly different from this species and are now considered as representatives of H. litchi. Another sheathoid nematode population from Florida, considered to be H. mangiferae by McSorley et al. (1980), was also found to be morphologically and molecularly congruous with H. litchi. During nematological surveys in Florida, a new sheathoid nematode was detected on date palms imported from California into Florida and is described herein as H. phoenicis sp. n. This new species is related morphologically to the H. strictathecatus morphotype with pointed tail terminus. Both have a stylet longer than 70 μm. The new species is phylogenetically related to H. strictathecatus and H. litchi. It differs morphologically from other Hemicriconemoides species by the cuticular ornamentation of the annuli, which are marked by coarse longitudinal ridges, grooves and thick margins. Morphological and molecular characterisations of H. cocophillus from Mozambique and Florida, USA are also elucidated in this study. New phylogenies of the genus Hemicriconemoides as inferred from the analyses of the ITS rRNA, D2-D3 of 28S rRNA and partial coxI gene sequences are provide