MOLECULAR AND MORPHOLOGICAL SYSTEMATICS AND IDENTIFICATION OF IMPORTANT PLANT PARASITIC NEMATODES
Title: Description of Globodera ellingtonae n. sp. (Nematoda: Heteroderidae) from Oregon
Submitted to: Journal of Nematology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 14, 2012
Publication Date: July 25, 2012
Citation: Handoo, Z.A., Carta, L.K., Skantar, A.M., Chitwood, D.J. 2012. Description of Globodera ellingtonae n. sp. (Nematoda: Heteroderidae) from Oregon. Journal of Nematology. 44(1):40-57.
Interpretive Summary: Plant-parasitic nematodes are microscopic worms that attack plant roots and cause an estimated ten billion dollars of crop loss each year in the United States and 100 billion dollars globally. Cyst nematodes are an important group, damaging the roots of many kinds of plants worldwide. In the present study, ARS scientists describe the anatomical and molecular features of a new cyst nematode that was discovered in soil samples collected during surveys to detect potato cyst nematode (PCN). This research is significant because the new species shares key anatomical features with two PCN species of regulatory concern, the pale potato cyst nematode and the golden nematode. The newly described species can confound accurate diagnosis of PCN because current molecular tests are not set up to identify it. The morphological and molecular data describing this lookalike species will help scientists, regulators, and extension agencies to more accurately identify and prevent the spread of potato cyst nematodes.
A new species of cyst nematode, Globodera ellingtoni, is described from soil collected from a field with a cropping history including potatoes in Oregon. It is characterized in having second-stage juveniles (J2) with a body length of 450 um (365-515), stylet length of 20.9 um (19-22.5) with basal knobs rounded with a greater height and with a forward projection on anterior side, lateral field with 4 lines, tail 46.7 um (39-55), hyaline tail terminus 24.3 um (20-32.5), and a tail tapering uniformly but abruptly narrowing with a constriction near the posterior third of the hyaline portion, ending with a peg-like finely rounded to pointed terminus. Cysts are spherical to sub-spherical, dark to light brown and circumfenestrate; the cyst wall pattern is ridge-like with heavy punctations. Males have a stylet length of 22.9 um (21-25); spicules measure 33.5 um (30-37) with a pointed thorn-like tip. Females have a stylet length of 21.3 um (20-22.5), one head annule and labial disc, heavy punctations on the cuticle, and short vulval slit 7.8 um (7.5-8). Morphologically, this new, round-cyst species differs from the closely related species G. pallida, G. rostochiensis, G. tabacum complex and G. mexicana by its distinctive J2 tail, cyst morphology including Granek’s ratio and the number of cuticular ridges between the anus and vulva, the stylet length in J2 and females and males, the shape and length of spicules, and the number of refractive bodies in the hyaline tail terminus of J2. Based upon analysis of ribosomal internal transcribed spacer (ITS) sequences, G. ellingtoni n. sp. is distinct from G. pallida, G. rostochiensis, G. tabacum and G. mexicana. Bayesian and Maximum Parsimony analysis of cloned ITS rRNA gene sequences indicated three clades, with maximum intraspecific variability as high as 2.8%. In silico analysis revealed ITS restriction fragment length polymorphisms for enzymes Bsh1236I, HinfI, and RsaI that overlap patterns for other Globodera species. Additional observations of two similar Globodera populations collected from soil from two fields in Idaho are given.