Morphological and molecular characterisation and diagnostics of some species of Scutellonema Andrássy, 1958 (Tylenchida: Hoplolaimidae) with a molecular phylogeny of the genus

Abstract

Scutellonema spp. are widely distributed across tropical and subtropical regions of the world and are associated with numerous agricultural and horticultural crops. Identification of many Scutellonema species is not always reliable, in part because many species share very similar diagnostic characters. In this study, we provide morphological and molecular characterisation of S. brachyurus from the USA and South Africa, S. bradys from Nigeria and three unidentified species from California, USA, New Zealand and Burkina Faso. Morphological descriptions, measurements, light and scanning electron microscopic photos and drawings are given for S. brachyurus. Females of S. brachyurus from the USA (type A) and South Africa (type B) showed a significant variation in the number of sectors and blocks on the lip annuli, ranging from about 4-12 and from 8-20, respectively. Molecular analysis using the D2-D3 of 28S rRNA, ITS rRNA and the COI mtDNA gene sequences revealed two distinct genotypes within S. brachyurus samples: type A (samples from USA, Italy, Korea, Taiwan) and type B (South Africa). Multivariate analyses determined that S. brachyurus from the USA and Taiwan (type A) differed from that from South Africa (type B) mainly in body, tail and DGO lengths, and ratios b′, c′, c and V. Phylogenetic relationships within Scutellonema are given as inferred from the analyses of the D2-D3 of 28S rRNA, ITS rRNA and the COI mtDNA gene sequences. PCR-RFLP diagnostic profiles and PCR with species-specific primers are developed for the studied Scutellonema species.

Morphological and molecular characterisation of Criconemoides brevistylus Singh & Khera, 1976 and C. obtusicaudatus Heyns, 1962 from South Africa (Nematoda: Criconematidae) with first description of a male C. obtusicaudatus and proposal of new synonyms

“…A phylogenetic tree reconstructed by the BI method for the D2-D3 of 28S rRNA gene sequences is presented in Figure 5. The phylogenetic relationships within this group were generally congruent with those reconstructed by Subbotin et al (2005) and Van den Berg et al (2011) in the tree for the suborder Criconematina. Criconemoides brevistylus formed a highly supported clade (PP = 98) with C ornatus.…”

Characterisation of some Scutellonema species (Tylenchida: Hoplolaimidae) occurring in Botswana, South Africa, Costa Rica and the USA, with description of S. clavicaudatum sp. n. and a molecular phylogeny of the genus

“…Fourteen Scutellonema species are currently reported from South Africa: S. africanum Smit, 1971, S. bizanae Van den Berg & Heyns, 1973, S. brachyurus, S. cavenessi, S. clathricaudatum Whitehead, 1959, S. commune Van den Berg & Heyns, 1973, S. dreyeri Van den Berg & De Waele, 1990, S. nigermontanum Van den Berg, 1990, S. sofiae Van den Berg & Heyns, 1973, S. sorghi Van den Berg & De Waele, 1990, S. transvaalense Van den Berg, 1981, S. truncatum Sher, 1964, S. tsitsikamense Van den Berg, 1976and S. unum Sher, 1964. In South Africa, S. brachyurus has a wide geographical distribution and is the only species of the genus that has been molecularly characterised so far in the country (Van den Berg et al, 2013). The South African populations of S. brachyurus are genetically different from those from USA and other world regions and also show some differences in their morphometrics.…”

Morphological and molecular characterisation of one new and several known species of the reniform nematode, Rotylenchulus Linford & Oliveira, 1940 (Hoplolaimidae: Rotylenchulinae), and a phylogeny of the genus

“…The 18S, ITS and the D2 and D3 expansion segments of 28S rRNA genes have been shown to be markers in the characterisation of phylogenetic relationships within Hoplolaimidae (Subbotin et al, 2007) and, especially, in cases where morphological characters may lead to cryptic diversity (Vovlas et al, 2008;Cantalapiedra-Navarrete et al, 2013;Palomares-Rius et al, 2014). Similarly, mitochondrial DNA (mtDNA), particularly the proteincoding mitochondrial gene, cytochrome c oxidase subunit 1 (coxI), has proved to be a powerful tool for providing accurate species identification and assessing phylogenetic patterns across the family Hoplolaimidae (Cantalapiedra-Navarrete et al, 2013;Van den Berg et al, 2013). However, although R. reniformis has been intensively sequenced because of its economic importance, little or no information on molecular markers is available for other Rotylenchulus species.…”