Morphological and Molecular Characterization of Two Aphelenchoides Endophytic in Poplar Leaves

Abstract

During a long-term, large network study of the ecology of plant endophytes in native habitats, various nematodes have been found. Two poplar species, Populus angustifolia (narrowleaf cottonwood) and Populus trichocarpa (black cottonwood), are important ecological and genomic models now used in ongoing plant-pathogen-endophyte interaction studies. In this study, two different aphelenchid nematodes within surface-sterilized healthy leaves of these two Populus spp. in northwestern North America were discovered. Nematodes were identified and characterized microscopically and molecularly with 28S ribosomal RNA (rRNA) and 18S rRNA molecular markers. From P. angustifolia, Aphelenchoides saprophilus was inferred to be closest to another population of A. saprophilus among sequenced taxa in the 18S tree. From P. trichocarpa, Laimaphelenchus heidelbergi had a 28S sequence only 1 bp different from that of a Portuguese population, and 1 bp different from the original Australian type population. The 28S and 18S rRNA trees of Aphelenchoides and Laimaphelenchus species indicated L. heidelbergi failed to cluster with three other Laimaphelenchus species, including the type species of the genus. Therefore, we support a conservative definition of the genus Laimaphelenchus, and consider these populations to belong to Aphelenchoides, amended as Aphelenchoides heidelbergi n. comb. This is the first report of these nematode species from within aboveground leaves. The presence of these fungal-feeding nematodes can affect the balance of endophytic fungi, which are important determinants of plant health.

Description of Aphelenchoides giblindavisi n. sp. (Nematoda: Aphelenchoididae), and Proposal for a New Combination

“…By having five lines in lateral fields, the new species comes close to two species sharing the same feature namely A. paramonovi and A. shamimi. By having a warty mucro at tail end and similar ranges of morphometric data, the new species comes close to A. ensete Swart, Bogale & Tiedt, 2000, A. fuchsi Esmaeili et al, 2016a, A. haguei Maslen, 1979, A. hei-delbergi (Zhao et al, 2007) Carta et al, 2016, A. huntensis Esmaeili et al, 2016b, A. paraxui Esmaeili et al, 2017a xui Wang et al, 2013. The comparisons with the aforementioned species are as follows:…”

“…During recent years, revisions have been performed on taxonomic status and placement of some Aphelenchoides species. In a recent study, the species Laimaphelenchus heidelbergi Zhao et al, 2007 was transferred to the genus Aphelenchoides (Carta et al, 2016). In another study, the species Tylaphelenchus christinae Lieutier and Laumond, 1978 was transferred to the genus Aphelenchoides (Pedram et al, 2018a(Pedram et al, , 2018b and finally, two species A. subtenuis (Cobb, 1926) Steiner and Buhrer, 1932 and A. arachidis Bos, 1977 have been transferred to the genus Robustodorus Andrássy, 2007(Kanzaki et al, 2018.…”

Beech leaf disease symptoms caused by newly recognized nematode subspecies Litylenchus crenatae mccannii (Anguinata) described from Fagus grandifolia in North America

“…While foliar nematodes are fairly common, nematodes that exist high in the tree canopy are not well‐known, though endophytic Aphelenchoides were recently discovered in poplar leaves ( Populus sp.) (Carta, Li, Skantar, & Newcombe, ). Nematodes like Litylenchus crenatae mccannii ssp.…”

First report with morphometrics and molecular characterization of phtyonematodes associating mango trees in the tropics of Saudi Arabia

“…Accordingly, the integration of morphometrics, morphological and molecular tools is being the most effective in the nematode characterization (De Ley et al, 2005, Handoo and Palomares-Rius, 2014). Many workers have successfully identified many different nematode species following the classical methods and confirmed their identification using 28S rRNA sequence data (Handoo and Palomares-Rius, 2014, Carta et al, 2016).…”