DNA barcoding evidence for the North American presence of alfalfa cyst nematode, Heterodera medicaginis.

Thomas Powers,Tim Harris,Saad Hafez,Kirsten Powers,Peter Mullin,Tim Todd,Zafar Handoo,Rebecca Higgins,Andrea Skantar

doi:10.21307/jofnem-2019-016

Thomas Powers, Tim Harris + Show 7 more

Open Access

https://doi.org/10.21307/jofnem-2019-016

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Abstract

Specimens of Heterodera have been collected from alfalfa fields in Kearny County, Kansas & Carbon County, Montana. DNA barcoding with the COI mitochondrial gene indicate that the species is not Heterodera glycines, soybean cyst nematode, H. schachtii, sugar beet cyst nematode, or H. trifolii, clover cyst nematode. Maximum likelihood phylogenetic trees show that the alfalfa specimens form a sister clade most closely related to H. glycines, with a 4.7% mean pairwise sequence divergence across the 862 nucleotides of the COI marker. Morphological analyses of juveniles and cysts conform to the measurements of H. medicaginis, the alfalfa cyst nematode originally described from the USSR in 1971. Initial host testing demonstrated that the nematode reproduced on alfalfa, but not on soybeans, tomato, or corn. Collectively, the evidence suggests that this finding represents the first record of H. medicaginis in North America. Definitive confirmation of this diagnosis would require COI sequence of eastern European isolates of this species.

Highlights

J2 stages of H. medicaginis and H. glycines Ichinohe 1952, it was determined that H. medicaginis possessed a longer stylet (25 μm vs 23 μm in H. glycines)
A follow-up of these reports, utilizing morphology, host trials, and DNA barcoding using the mitochondrial gene COI along with ITS1, the transcribed spacer region between 18S and 5.8S of the nuclear ribosomal repeat region, and the heat shock protein gene Hsp90 provide supporting evidence that Heterodera medicaginis is present in the US
A DNA record from a molecular survey from a Montana alfalfa field suggests the distribution may be wider than a single river valley in Kansas

Summary

Introduction

J2 stages of H. medicaginis and H. glycines Ichinohe 1952, it was determined that H. medicaginis possessed a longer stylet (25 μm vs 23 μm in H. glycines). The cyst stage of H. medicaginis was notable because of its ‘weakly developed, unbranched underbridge’ (Gerber and Maas, 1982). A DNA sequence of the internal transcribed spacer region was submitted to GenBank (Subbotin et al, 2001). During the last five years, there have been unpublished reports of a cyst species reproducing on alfalfa (https://nematode.unl.edu/hetemedic.htm) in the Great. A follow-up of these reports, utilizing morphology, host trials, and DNA barcoding using the mitochondrial gene COI along with ITS1, the transcribed spacer region between 18S and 5.8S of the nuclear ribosomal repeat region, and the heat shock protein gene Hsp provide supporting evidence that Heterodera medicaginis is present in the US

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