Reniform nematode

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Scientific Name: Rotylenchulus reniformis Linford and Oliveira

 

Taxonomy

 

Class

Secernentea

Order Tylenchida
Superfamily Tylenchoidea
Family Hoplolaimidae
Genus Rotylenchulus

Geographical distribution

Reniform nematode is a very common, damaging pest of many plants in subtropical/tropical soils and sometimes occurs in protected temperate soil.

Economic importance

The first report that R. reniformis is pathogenic to sweetpotato was made by Martin (1960). In sweetpotato, losses range from 44-60%, depending on initial population. 

Symptoms

The reniform nematode causes root necrosis resulting in severe root pruning and subsequent dwarfing of plants. Fibrous or feeder roots are mostly attacked which may reduce the absorption ability and other physiological functions of the plant. This may lead to stunting, yellowing and wilting. In some cases, the nematode may produce lesions, distortions or cracks on storage roots which reduce marketability.

Morphology

R. reniformis is sexually dimorphic. The immature female is free in soil, measures 0.3-0.5 mm long, and C-shaped when killed by heat. The lip region is rounded to conoid, continuous with the body contour and moderately sclerotised. The stylet is 10-20 Ķm long, of moderate strength and with small rounded basal knobs. There is opening of dorsal oesophageal gland, about a stylet length, behind the stylet base. The oesophagus has well developed median bulb and elongated (4-5 body widths) gland lobes, overlapping intestine laterally and ventrally. The vulva posterior (V= 58-72) has paired, opposed gonads, each with a double flexture in the ovary. The tail conoid with rounded terminus is 2-3 anal body widths long. The mature female is semi-endoparasitic in roots, greatly swollen, irregular to kidney-shaped, and has enlarged gonads occupying much of body. The male lip sclerotisation and stylet are much weaker than the immature female. Its oesophagus degenerates and it has a tail similar to immature female, has small adanal bursa, slender and with curved spicules.

Life cycle

Juveniles of the reniform nematode are differentiated within the egg and undergo one moult before the second stage juveniles hatch. Three additional moults occur without feeding while the juveniles are free in the soil. Adult stage and egg production occur 16 days after inoculation in susceptible cultivars. The life cycle from egg to egg is from 22-29 days in susceptible cultivars such as V20-436.

Ecology

Male and female nematodes can survive in air-dried soil kept at 20-25oC for 7 months. Local dissemination is through infested soil. Distribution is limited by low winter temperatures, and nematode and disease development are both greater at 29.5oC than at 15, 21.5 or 36oC.

Host range

Very wide host range including weeds. Major host are soybean, cowpea, cotton, pineapple, sweetpotato, cassava and other vegetable crops.

Management

Cultural control

Crop rotation.Non-host crops or resistant crops can be planted when nematode population is high.

Use of organic amendments.

Use of trap and antagonistic crops. Planting Tagetes erecta and Crotolaria spectabilis in nematode infested soil has been found effective against the nematode.

Biological control

Paecilomyces lilacinus, a fungal egg parasite was found effective against the reniform nematode.

Host-plant resistance

The following Philippine cultivars/lines are found resistant to the reniform nematode: CI 951-6, BNAS 551, VSP-1, V29-1166, CI 916-455, UPLB 80, Kabiti and CI-950-27.

Chemical control

Several nematicides have been reported to be effective against the reniform nematode. Examples are Nemagon, Mocap, Dasanit, Nemacur, Furadan, Temik, Vydate.

 

References

Ayala, A. and Ramirez, C.T. 1964. Host-range, distribution and bibliography of the reniform nematode Rotylenchulus reniformiswith special reference to Puerto Rico. J. Agric. Univ. P.R. 48:140-161.

Birchfield and Martin, 1968. Evaluation of nematicides for controlling nematodes of sweetpotatoes. Plt. Dis. Rept. 52:127-131.

Dela Cruz, C.S.1988. Reactions of sweetpotato (Ipomoea batatas Lam.) cultivars to reniform nematode, Rotylenchulus reniformis, and determinants of resistance mechanisms. M.S. Thesis. UPLB. 68 p.

Evans, K, D. L. Trudgill and J. M. Webster. 1993. Plant Parasitic Nematodes in Temperate Agriculture. University Press, Cambridge. 648 p.

Galano, C. D., R. M. Gapasin and J. L. Lim. 1996. Efficacy of Paecilomyces lilacinus isolates for the control of root-knot nematode (Meloidogyne incognita (Kofoid and White) Chitwood) in sweetpotato. Annals of Tropical Research 18: 4-12.

Gapasin, R. M. and R. B. Valdez. 1979. Pathogenicity of Meloidogyne spp. and Rotylenchulus reniformis on sweetpotato. Annals of Tropical Research 1:20-26.

Gapasin, R. M. 1984. Resistance of fifty-two sweetpotato (Ipomoea batatas (L.) Lam.) cultivars to Meloidogyne incognita and M. javanica. Annals of Tropical Research 6: 1-19.

Martin. 1960. The reniform nematode may be a serious pest of the sweetpotato. Plt. Dis. Rept. 44:216.

Sasser, J. N. and C. C. Carter. 1985. An Advanced Treatise on Meloidogyne. Vol. I: Biology and Control. North Carolina State University Graphics. 422 p.

Sasser, J. N. 1989. Plant Parasitic Nematodes: The Farmerís Hidden Enemy. University Graphics, North Carolina State University, Raleigh, N. C. 115 p.

 

 

Contributed by: Ruben Gapasin

Taxonomy

Economic importance

Geographical distribution

Symptoms

Morphology

Life cycle

Ecology

Host range

Management

References

Susceptible cultivar (right) with death of fibrous roots and smaller storage root (C. de la Cruz).

 

 

Storage root cracking associated with reniform nematodes ( C. Clark, APS).