MOLECULAR AND MORPHOLOGICAL SYSTEMATICS AND IDENTIFICATION OF IMPORTANT PLANT PARASITIC NEMATODES
Title: Supplemental description of Paraphelenchus acontioides Taylor and Pillai, (Tylenchida: Paraphelenchidae), with ribosomal DNA trees and a morphometric compendium of female Paraphelenchus
Submitted to: Nematology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 7, 2011
Publication Date: November 11, 2011
Citation: Carta, L.K., Skantar, A.M., Handoo, Z.A., Baynes, M.A. 2011. Supplemental description of Paraphelenchus acontioides Taylor and Pillai, 1967 (Tylenchida: Paraphelenchidae), with ribosomal DNA trees and a morphometric compendium of female Paraphelenchus. Nematology. 13(8):887-899.
Interpretive Summary: There are a wide variety of microscopic roundworms called nematodes which inhabit agricultural fields. Although many cause global crop losses exceeding $100 billion annually, others are found in above-ground plant parts where they may feed on fungi that may be good or bad for crops. A major problem with determining the role of these fungal-feeding nematodes is that the anatomical descriptions and keys used for their identification are outdated and unreliable. In this study, ARS scientists from Beltsville, Maryland, and an ecologist from the University of Idaho in Moscow, identified and described a nematode from cheatgrass weeds, major problems in western wheat and alfalfa. They compiled information on anatomical features for twenty-three previously described nematode species, and they also characterized the DNA of the nematode to build a family tree for this group of nematodes. These results are significant because they provide the details necessary for identifiers and ecologists to confidently name these species wherever they may occur in the world. This information will be used by scientists, extension agents and pest managers engaged in nematode and weed research and control.
Nematodes were isolated from surface-sterilized stems of cheatgrass, Bromus tectorum L. (Poaceae) in Colorado, grown on Fusarium (Hypocreaceae) fungus culture, and identified as Paraphelenchus acontioides Taylor and Pillai, 1967. Morphometrics and micrographic morphology of this species are given to supplement the original description and expand the comparative species diagnosis. A tabular morphometric compendium of the females of the 23 species of Paraphelenchus is provided since the last diagnostic compilation of 1984. The structure of the anterior median bulb in this species and others observed shows the discontinuity and less fibrous histological difference that characterized Paraphelenchus amblyurus Steiner, 1934 are not unique but common within the Aphelenchidae. Variations in the oviduct within the genus are reviewed to evaluate the taxonomic assignment of Paraphelenchus deckeri (Zeidan & Geraert, 1992) Andrássy, 2007, a morphologically transitional species between Aphelenchus and Paraphelenchus. Sequences were generated for both 18S and 28S ribosomal DNA, representing the first identified species within Paraphelenchus so characterized. These sequences were incorporated into phylogenetic trees with related species of Aphelenchidae, and Aphelenchus avenae isolates formed a well-supported monophyletic sister group to Paraphelenchus. The ecology of Paraphelenchus, cheatgrass and Fusarium is also discussed.