Morphological and molecular characterisation of some Hemicriconemoides species (Nematoda: Criconematidae) together with a phylogeny of the genus

Abstract

Sheathoid nematodes of the genusHemicriconemoidesare migratory root-ectoparasites of many plants including various agricultural crops and fruit trees. They are generally found inhabiting warm areas of the world and presently consist of 52 valid species. In this study we provide morphological and molecular characterisation of 12 species of this genusviz.:H. alexis,H. brachyurus,H. californianus,H. chitwoodi,H. macrodorus,H. minutus,H. ortonwilliamsi,H. promissus,H. silvaticus,H. strictathecatus,H. wessoniandHemicriconemoidessp. originating from China, Greece, Japan, Myanmar, Spain, South Africa and the USA. Morphological descriptions, measurements, light and scanning electron microscopic observations and drawings are given for several species. Phylogenetic relationships withinHemicriconemoides, as inferred from the analyses of the D2-D3 of 28S rRNA and ITS-rRNA gene sequences, resulted in trees with three major clades that corresponded with species groupings based on morphology of the lip pattern and vulval flap. PCR with species-specific primers were developed forH. californianus,H. chitwoodiandH. strictathecatus.

Species discovery and diversity in Lobocriconema (Criconematidae: Nematoda) and related plant-parasitic nematodes from North American ecoregions

“…Lack of evidence for widespread longdistance dispersal contrasts with explanations of distribution for nematodes associated with agricultural commodities. It is well-documented that agricultural commerce has spread species of plant-parasitic nematodes (O'Bannon 1977;Steiner et al 1951;Van den Berg et al 2014). This study of Lobocriconema species illustrates that plant-parasitic nematodes can have a complex phylogeographic structure similar to other plants and animals.…”

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

“…These sheathoid nematodes included those indicated as H. strictathecatus from China, South Africa and Venezuela (Van den Berg et al, 2014). A few specimens of a population morphologically similar to H. cocophillus were found in Key West mixed with topotype specimens of H. strictathecatus.…”

“…Other species and populations included in this study and compared with Florida populations were listed and analysed in Van den Berg et al (2014). These sheathoid nematodes included those indicated as H. strictathecatus from China, South Africa and Venezuela (Van den Berg et al, 2014).…”

“…PCR and sequencing protocols were described by Tanha Maafi et al (2003). The primer sets used for amplification of the D2-D3 expansion segments of 28S rRNA and ITS-rRNA genes are given by Van den Berg et al (2014). Partial coxI gene was amplified by primer set: COIF5 (5 -AAT WTW GGT GTT GGA ACT TCT TGA AC-3 ) and COIR9 (5 -CTT AAA ACA TAA TGR AAA TGW GCW ACW ACA TAA TAA GTA TC-3 ) as described by Powers et al (2014).…”

“…Sheathoid nematode populations with shorter stylets (62.5-72.0 μm, cumulated range values of three populations) than that of H. strictathecatus (73-83 μm) and anchor-shaped knobs, but with rounded tail terminus, have been reported in South Africa and also in China, Taiwan and Venezuela. These populations were characterised morphologically and molecularly and were proposed to be considered H. strictathecatus by Subbotin et al (2005) and Van den Berg et al (2014), in spite of the fact that no DNA sequences of topotype specimens of H. strictathecatus were available at the time to validate this morphological identification.…”