Occurrence and Host Range of a New Root-Knot Nematode (Meloidogyne chitwoodi) in the Pacific Northwest

Meloidogyne chitwoodi is a root-knot nematode that parasitizes a broad range of plants. In the Pacific Northwest (PNW) of the United States, M. chitwoodi is a major potato pest. The nematodes infect roots and tubers; blemishes caused by the nematodes on the tubers significantly affect potato marketability. M. chitwoodi is a quarantine pathogen by many regulatory agencies, limiting potato trade opportunities when it is present. A loop-mediated isothermal amplification (LAMP) assay was developed to amplify the intergenic spacer (IGS2)-18S region of the ribosomal rDNA of M. chitwoodi. Using the LAMP assay, we could detect the presence of M. chitwoodi from infected Washington State soil samples. The LAMP primers showed specificity for DNA from M. chitwoodi and the closely related species M. fallax. There was no cross reaction of the LAMP primers with DNA from tropical nematodes M. incognita, M. arenaria, and M. javanica, or the Northern root-knot nematode M. hapla. The LAMP assays can be completed within 45 min, and they were 100 times more sensitive in nematode detection than conventional PCR. The LAMP assay will facilitate detection of potato nematodes M. chitwoodi and M. fallax. Knowledge of potato nematodes, particularly M. chitwoodi in PNW soils, will aid management decisions.

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PRELIMINARY STUDIES OF THE TRANSFER OF FOUR STRAINS OF DITYLENCHUS DIPSACI (KÜHN 1858) FILIPJEV 1936

Canadian Journal of Research ◽

10.1139/cjr37c-014 ◽

1937 ◽

Vol 15c (4) ◽

pp. 168-174

Author(s):

R. J. Hastings ◽

Wm. Newton

Keyword(s):

Host Range ◽

Host Specificity ◽

Pacific Northwest ◽

Red Clover ◽

Infested Soil ◽

The Pacific ◽

Limited Host Range ◽

Ditylenchus Dipsaci ◽

Tissue Reactions ◽

Test Plants

The bulb and stem nematode, Ditylenchus dipsaci, attacks narcissus, iris, red clover and strawberry in the Pacific Northwest. The isolations from each of these important crops are herein described as strains.Preliminary studies of the transfer of these strains establish the existence of three strains of D. dipsaci in the Pacific Northwest, viz.:(i) Red clover strain; characterized by causing swollen crowns and stunt in red clover seedlings.(ii) Strawberry strain; characterized by a limited host range, swollen crowns in strawberry seedlings, and entrance into red clover seedlings without visible tissue reactions.(iii) Narcissus and iris strain; characterized by a wide host range and entrance into clover and strawberry seedlings without visible tissue reactions.No satisfactory technique of establishing the host range of the biological strains of D. dipsaci has been developed. The clamping of glass rings filled with a nematode suspension in moist pulverized peat to the foliage of test plants did not affect the test plants in a constant manner. The examination of seedlings after clarification in a lacto-phenol solution containing acid fuchsin gave more constant results. The seedlings were removed from infested soil shortly after they appeared above ground.The reports of host specificity of the red clover strain were not confirmed, for the red clover strain entered white clover and alfalfa, hitherto considered resistant. Likewise, the reports of host specificity of the narcissus strain were not supported by our experimental results. The narcissus strain entered red clover and oats, also considered resistant hitherto.

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Nematode Genome Announcement: Draft genome of Meloidogyne chitwoodi, an economically important pest of potato in the Pacific Northwest

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-12-20-0337-a ◽

2021 ◽

Author(s):

Sapinder Bali ◽

Shengwei Hu ◽

Kelly Vining ◽

Charles R Brown ◽

Hassan Majtahedi ◽

...

Keyword(s):

Pacific Northwest ◽

Draft Genome ◽

Single Copy ◽

Economic Losses ◽

Meloidogyne Chitwoodi ◽

The Pacific ◽

Important Pest ◽

Genome Assemblies ◽

The U.S ◽

Nematode Genome

Meloidogyne chitwoodi is one of the most devastating pests of potato in the U.S. Pacific Northwest (PNW). Nematode-infected tubers develop external as well as internal defects, making the potatoes unmarketable, and resulting in economic losses. Draft genome assemblies of three M. chitwoodi genotypes, Mc1, Mc2 and Mc1Roza, were generated using Illumina and PacBio Sequel RS II sequencing. The final assemblies consist of 30, 39 and 38 polished contigs for Mc1, Mc2 and Mc1Roza, respectively, with average N50 of 2.37 Mb and average assembled genome size of ~47.41 Mb. An average of 10,508 genes were annotated for each genome. BUSCO analysis indicated that 69.80% of the BUSCOs were complete whereas 68.80%, 0.93% and 12.67% were single copy, duplicated and fragmented, respectively. These highly contiguous genomes will enrich resources to study potato-nematode interactions and enhance breeding efforts to develop nematode resistant potato varieties for PNW.

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