Rotylenchulus reniformis

Taxonomy, Common Name, Disease

Historical

Linford and Oliveira (1940) first discovered this nematode in cowpea in Hawaii.

Hosts

Very broad host range (fruit trees, cotton, cowpea, tea, and soybean; pineapple in Hawaii).

Distribution

Tropical and subtropical countries. West and Central Africa; Central and South America; Southeast Asia; In U.S. an important pest in Hawaii, the Southeastern U.S., and Texas.

Life Cycle

Sedentary endoparasite, bisexual, amphimictic. Eggs are laid in a gelatinous matrix, 40-60 eggs per mass. Eggs hatch in 8-10 days, then juveniles undergo 3 molts in the soil without feeding. Young females are the infective stage and only females are parasitic. Females enter root with posterior outside, feed and swell to reniform shape. There is a 1:1 sex ratio, and males do not feed (have vestigial stylet only). Copulation assumed to take place, but there is also some evidence of parthenogenesis. The life cycle is completed in 25 days at 25 C (80 F). Nurse cells (100-200 per female) form near pericycle. Feeding causes hypertrophy of pericycle and endodermis cells, increased cytoplasm density, but cells remain uninucleate with large nucleolus. Walls may rupture to form a syncytium. Syncytium about 2 cells deep may extend half way around root in soybeans. Nematode invasion stimulates synctia primarily in pericycle tissues (phase 1: cell wall lysis; phase 2: anabolic phase - increase in organelles of affected cells).

Symptoms-Pathogenicity

In Louisiana, R. reniformis causes a 40-60% reduction in cotton yield, with a concomitant increase in Fusarium wilt. In the presence of this nematode, Fusarium wilt-resistant varieties of cotton also become susceptible.

Management

Preplant nematicides. Resistant varieties - soybean - Peking, Dyer, Custer, Pickett - hypersensitive response to nematode, no increase in metabolic activity. Cultural - break anhydrobiotic survival stage by pre-irrigation 3 months before pineapple - increase decline .

Importance

Quarantine pest in California. Most important nematode pest of pineapple in Hawaii.

Characteristics

Characteristics: Rotylenchulus - Sexually dimorphic. Immature female free in soil, - 0.3-0.5 mm long, C-shaped when killed by heat. Lip region rounded to conoid continuous with body contour, moderately sclerotized; stylet 10-26 um long, of moderate strength with small rounded basal knobs. Opening of dorsal esophageal gland about a stylet length behind stylet base. Esophagus with well developed median bulb and elongated (4-5 body widths) gland lobes overlapping intestine laterally and ventrally. Vulva posterior (V = 58-72) with paired, opposed gonads each with a double flexure in the ovary; tail conoid with rounded terminus, 2-3 anal body widths long. Mature female, endoparasitic in roots, greatly swollen, irregular to kidney shaped, enlarged gonads occupying much of body. Male lip sclerotization and stylet much weaker than immature female, esophagus degenerate, tail similar to immature female with small adanal bursa; spicules curved, slender.

References

  1. 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.
  2. Siddiqi, M.R. 1972. Rotylenchulus reniformis. C.I.H. Descriptions of Plant-parasitic Nematodes. Set 1, No. 5. Commonwealth Institute of Parasitology. C.A.B. International. 2r-Verlag, New York. 372 pages. (page 184)tology. Springer-Verlag, New York. 372 pages. (page 184)