Morphological and molecular characterization of Paratylenchus beltsvillensis n. sp. (Tylenchida: Paratylenchidae) from the rhizosphere of pine tree (Pinus virginiana Mill) in Maryland, USA.

Mihail R Kantor,Sergei A Subbotin,Gary R Bauchan,Zafar A Handoo,Joseph D Mowery

doi:10.21307/jofnem-2021-079

Abstract

The pin nematode, Paratylechus beltsvillensis n. sp. collected from rhizosphere soil of a Virginia pine tree (Pinus virginiana Mill) growing in Little Paint Branch Park, Beltsville, Prince George’s County, Maryland, USA, is described and illustrated along with light and scanning electron photomicrographs. Females, males, and juveniles of this new species were recovered from soil samples using the sugar centrifugal flotation and Baermann funnel extraction methods. Morphologically, females are short, body length ranging from 245 to 267 μm, stylet from 70 to 75 μm long with anchor shaped knobs, vulva located at 70–73% and small vulval flap, spermatheca large, and ovoid filled with sperms. Lateral field with three incisures, of which the outer two are prominent. Tail slender, having a rounded tail terminus. Males without stylet and have a degenerated pharynx, spicules = 17–20 µm and gubernaculum = 5.0–5.5 µm. Both morphological observations and molecular analysis of ITS and partial 28S ribosomal RNA gene sequences indicated that the specimens collected from the soil at Beltsville Park from rhizosphere soil samples from Virginia pine represents a new pin nematode species.

Highlights

Wang et al (2016a), using the ITS rRNA gene, demonstrated that their newly described species P. nanjingensis which has a 64–68 μm long stylet grouped with P. bilineatus and P. aculentus
An unknown Paratylenchus species with a long stylet was found in a rhizosphere soil of a Virginia pine tree (Pinus virginiana Mill) in Beltsville, Prince George’s County, Maryland, USA
Nematodes were observed with the low-temperature scanning electron microscopy (LT-SEM) using the techniques described in Kantor et al (2020) and Carta et al (2020)

Summary

Introduction

With the advent of molecular biology, phylogenetic studies have been conducted to examine the rela tionships among paratylenchids. Subbotin et al (2005) were the first to provide molecular characterization of several Paratylenchus species using partial 28S rRNA gene sequences. Lopez et al (2013) used the ITS1 rRNA gene to reconstruct paratylenchid relationships including G. bilineata Brzeski (1995) and G. aculenta (Brown, 1959; Raski, 1962). Van Den Berg et al (2014) inferred phylogenetic relationships among several Paratylenchus spp. using 28S rRNA (58 sequences) and ITS rRNA (40 sequences) gene sequences for this genus. Wang et al (2016a), using the ITS rRNA gene, demonstrated that their newly described species P. nanjingensis which has a 64–68 μm long stylet grouped with P. bilineatus and P. aculentus. Subbotin et al (2005) were the first to provide molecular characterization of several Paratylenchus species using partial 28S rRNA gene sequences. Wang et al (2016a), using the ITS rRNA gene, demonstrated that their newly described species P. nanjingensis which has a 64–68 μm long stylet grouped with P. bilineatus and P. aculentus. Munawar et al (2021), Singh et al (2021), Clavero-Camacho et al (2021) published comprehensive phylogenies of the genus Paratylenchus. These phylogenetic analyses did not support a justification of erection for the genus Gracilacus and this genus was considered as a synonym of Paratylenchus. The objective of this study was to describe this new species using light (LM) and scanning electron microscopy (SEM) and provide its molecular characterization

Objectives

Methods

Results