Location: Nematology Laboratory
Title: Occurrence of Meloidogyne fallax in North America, and molecular characterization of M. fallax and M. minor from U.S. golf course greens Authors
Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 14, 2013
Publication Date: N/A
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. Root-knot nematode (RKN) species are parasitic on a wide range of host plants, including alfalfa, turfgrasses, and numerous other crops. The anatomical features of many RKNs are similar and may confound accurate species identification. In this study, ARS scientists and colleagues from Arizona and Utah used anatomical features and molecular markers to identify and describe two populations of RKN from golf course turfgrass; one was a species not previously found in North America. This research is significant because new molecular information obtained for these populations will facilitate future identification of RKN. This report will aid researchers and diagnosticians in accurately identifying economically important root-knot nematodes that are difficult to tell apart by comparing anatomical features alone.
Technical Abstract: Several species of root-knot nematodes (Meloidogyne spp.) are known to have significant presence on turf grass in golf course greens, particularly in the western United States. Nematodes isolated from a golf course in King Co., Washington were identified as Meloidogyne minor based on analysis of the large ribosomal subunit (LSU 28S D2-D3 expansion segment), the internal transcribed spacers 1 and 2 (ITS-rDNA), the intergenic spacer region 2 (IGS2) and the nuclear protein-coding gene Hsp90. Sequence-characterized amplified region (SCAR) primers that were originally designed to be specific for M. fallax were found to cross-react with M. minor. A population from CA was determined to be M. fallax based on juvenile tail morphology and analysis of the ribosomal markers and Hsp90. Phylogenetic relationships of these populations and known root-knot nematode species based on alignments of Hsp90 genomic sequences were congruent with previous trees based on ribosomal genes, showing as good or better resolution of M. fallax and M. chitwoodi than can be obtained with 28S or 18S rDNA. The strengths and weaknesses of existing ribosomal markers, Hsp90, and the SCAR primers as diagnostic tools are discussed.