Morphological and Molecular Characterization of Paralongidorus sali Siddiqi, Hooper, and Khan, 1963 with a Description of the First-Stage Juvenile and Male of Longidorus jonesi Siddiqi, 1962 from China

Abstract

The family Longidoridae Thorne, 1935 comprises a group of migratory plant-parasitic species that damage a wide range of wild and cultivated plants through direct feeding on root cells and the transmission of several plant-pathogenic viruses (Decraemer and Robbins, 2007; Decraemer and Chaves, 2012). Members of these genera are known to transmit nepoviruses and are regulated by quarantine inspections in many countries (Gutiérrez-Gutiérrez et al., 2016). Longidorus and Paralongidorus belong to family Longidoridae, both are globally distributed and have 160 and 90 known species, respectively (Palomares-Rius et al., 2013; Archidona-Yuste et al., 2016; Esmaeili et al., 2016).

Some species of Paralongidorus have controversial status due to synonymization of Longidoroides (Khan et al., 1978) and Siddiqia (Khan et al., 1978), and some Paralongidorus species have been wrongly included and belong to genus Longidorus (Decraemer and Coomans, 2007). The major difference used to separate Longidorus, Longidoroides, and Paralongidorus is the shape of amphids (pouch like in Longidorus and Longidoroides vs. funnel/stirrup shaped in Paralongidorus) and the opening of amphidial aperture (pore-like in Longidorus vs. slit-like in Longidoroides and Paralongidorus) (Oliveira and Neilson, 2006). Several new species of Paralongidorus have published with complete molecular characterization and scanning electron microscopy (SEM) observations (Palomares-Rius et al., 2008, 2013; Pedram et al., 2012; Gutiérrez-Gutiérrez et al., 2017; Barsi and Luca, 2017) which enables the discrimination between Longidorus and Paralongidorus species. However, there is no molecular evidence to distinguish Longidoroides species which leaves the status of this genus as junior synonym of Paralongidorus as suggested by Decraemer and Coomans (2007).

During a routine nematological survey of Hangzhou, Zhejiang Province, eastern China, two populations of longidorid nematodes were isolated from the rhizosphere of woody perennials. The population isolated from Cyclobalanopsis glauca (Thumb.) Oerst, 4 juvenile stages were recovered and identified as Longidorus jonesi, the population from Castanopsis sclerophylla (Lindl.) Schottky, 3 juvenile stages were recovered and was identified as Paralongidorus sali.

Robbins et al. (1995) reported 3 juveniles stages of L. jonesi and no first stage juvenile or male were observed additionally this is the first report of genus Paralongidorus found in China. Therefore, the objectives of the present study were to: (i) provide updated morphological descriptions of first-stage juvenile P. sali, and male of L. jonesi, (ii) characterize the molecular data of both species using the D2–D3 expansion segments of 28S rRNA and partial 18S rRNA gene sequences, and (iii) demonstrate the phylogenetic relationships of both species with related species.