Paratrichodorus minor

Taxonomy, Common Name, Disease

Scientific name - Paratrichodorus minor

Common name - stubby root nematode

Disease - corky ring spot of potatoes

Historical

The name of this nematode has changed several times. Initially it was Trichodorus christiei, then Paratrichodorus christiei then Paratrichodorus minor followed by Nanidorus minor and now Paratrichodorus minor.

Hosts

Wide host range including alfalfa, azalea, boysenberry, vegetables, corn, tomato, onion, wheat, sugarcane, rice, grasses, etc. Vectors Tobacco Rattle virus. Poor hosts include orchard grass, rye, spinach, radish, strawberry, pea and tobacco. Non-hosts are asparagus, showy crotalaria, poinsettia and jimsonweed.

Distribution

Widely distributed in temperate to sub-tropical climates. Widespread in U.S. on many hosts. Rare in Europe.

Life Cycle

Migratory ectoparasite. Life cycle completed in 16-17 days at 30 C (86 F), 21-22 days at 22 C (72 F). Temperature range for reproduction is 15 to 30 C ( 68-95) F. Males are rare. Feeds over the whole of the root surface, but usually close to the root tip, including the root cap, the meristematic region, and the region of elongation; nematode pierces epidermal cell walls and root hairs with rapid thrusts (10 per second).

Symptoms-Pathogenicity

Feeding causes root tips to stop growing and appear " stubby".

Management

Preplant nematicides. This species is notorious for the speed at which it re-establishes itself after fumigation. Virus-free planting stock.

Importance

Stubby root nematode is widely distributed and can cause damage on many crops. Often found in fields that have other species of plant parasitic nematodes. Multiple nematode species in a single field increase the difficulty of developing resistant plant varieties because resistance genes are ususally effective against single genera or several species within a single genus. Injurious to carrot in California and to tomato and onion in the southeastern U.S. Transmission of tobacco rattle virus causes corky ringspot symptoms in potatoes.

Characteristics

Trichodorus - Female body stout 0.5-1.4 mm long, cigar-shaped especially when killed by heat. Cuticle thin and rather loose without obvious annulation or lateral fields. Mouth stylet an elongated ventrally curved tooth ; narrow anterior esophagus gradually expands into a glandular, spatulate, posterior bulb which abuts the intestine. Vulva usually median with strong vaginal sclerotization and musculature , gonads paired and opposed with reflexed ovaries; tail usually rounded, very short, the anus almost terminal. Males with elongate, ventrally curved spicules and a gubernaculum about a third the spicule length; bursa absent but three prominent ventro-median papillae opposite and anterior to the spicules; tail curls ventrally when killed by heat. Male esophageal region similar to female but with one to four prominent ventral papillae in the onchiostyle region in addition to the excretory pore. Paratrichodorus - Similar to Trichodorus but cuticle somewhat looser and swells more in acid fixatives. Posterior esophagus may overlap the intestine or intestine may extend forward over the basal bulb. Vaginal sclerotization and musculature much weaker than in Trichodorus. Males usually straight when killed by heat, bursa present, spicular and copulatory muscles much weaker than in Trichodorus.

References

  1. Jenkins, W.R. and D.P. Taylor. 1967. Chapter 20. Stubby-root Nematodes: Trichodorus. in Plant Nematology. Reinhold Publishing Corporation, New York. 270 pages. (page 204)
  2. Nickle, W.R. 1984. Chapter 9. Nematode Parasites of Vegetable Crops. in Plant and Insect Nematodes. Marcel Dekker, Inc. New York. 925 pages. (page 337)
  3. Heyns, J. 1975. Paratrichodorus christiei. C.I.H. Descriptions of Plant-parasitic Nematodes. Set 5, No. 69. Commonwealth Institute of Parasitology. C.A.B. International. 4 pages.
  4. Evans, K., D.L. Trudgill, and J.M. Webster. 1993. Chapter 1. Extraction, Identification and Control of Plant Parasitic Nematodes. in Plant Parasitic Nematodes in Temperate Agriculture. CAB International, UK. 648 pages.