Linford and Oliveira, 1940
History and significance
Rotylenchulus reniformis is a plant parasite nematode with a worldwide distribution in the tropical and subtropical regions. This nematode has a wide host range infecting plants in many species around the word. It belongs to the Family Hoplolaimidae; it was first observed on the roots of cowpea in Hawaii. The reniform nematode was described as new species in 1940 by Linford and Oliver after four years of investigations . It is called the reniform nematode because of the distinct kidney-shaped appearance of the mature female [2, 5]. R. reniformis is the only species of major economic importance to agriculture of the 10 Rotylenchulus species described .
Distribution and host range
R. reniformis has been found associated with hundreds of species of plants in tropical and subtropical areas. It has been reported in thousands of localities in South America, Central America, North America, the Caribbean Basin, Africa, Europe, India, Southeast Asia, Australia, China, Japan and the Philippines [8, 11]. Its wide distribution is due to the wide range of host it infects; including fruit trees, lentil, cotton, cowpea, pigeonpea, tea, tobacco, soybean, pineapple, bananas, okra, coconut, cabbage, sweet potato, alfalfa, corn, asparagus, palm, cucumber, tomato, pumpkin, squash, cassava, radish, eggplant, guava, melon and ginger [2, 5, 8]. Certain species of plants such as wild barley, mustard, oats, barnyard grass, pangola grass, red-hot and sweet pepper, spinach have been reported as non-host to reniform nematode [2, 5].
Reniform nematodes have esophageal glands overlapping the intestine, short stylet, a strongly developed framework; the dorsal esophageal gland orifice is located posterior to the stylet knobs [5, 10]. Immature females are slender, free in the soil. The body often assumes an open spiral or ‘C’ shape when killed by heat . Mature females have a swollen kidney-shaped body with a short tail, slender and short stylet, rounded knobs; with a three-part esophagus, a long and narrow isthmus, and well-developed metacarpus. The vulva is just behind the mid-portion of the body . Males are vermiform; they have a weak stylet and knobs, curved spicules and pointed tail; the esophagus is degenerate, with a reduced median bulb [2, 10].
R. reniformis is sedentary semi-endoparasite on roots of many plants [2, 3, 4]. Mature females penetrate partly into roots, leaving the posterior portion of their bodies projecting at the surface [2, 8]. Juveniles, males and immature females are found in soil . The immature female is the infective stage penetrating roots [2, 4]. Males are not parasites, they do not feed but they are important for reproduction . Under drought conditions, R. reniformis can survives 1–2 years without host by entering an anhydrobiotic state .
R. reniformis is sexually dimorphic; its life cycle is completed in 17 to 23 days under favorable temperatures . The developing juvenile (J1) molt once while still inside the egg shell [3, 8]; the eggs hatch in 8–10 days, then a J2 develops molting 3 times (J3 and J4) in the soil to become immature males and females [3, 6]. The anterior one-third of the young female body penetrates roots and forms a feeding site (syncytium) in the endodermis. The female continue to develop, swelling and becoming kidney-shaped . The female deposits eggs in a gelatinous matrix containing about 50 eggs on surface of the root after 7–10 days [6, 10].
Infective stage penetrates the epidermis and cortical parenchyma of the host root, only the anterior part of the body is embedded within root tissue. Penetration is stopped when lips reach the endodermis, resulting in formation of a trophic site that consist of a syncytium structure, which forms from an endodermal cell and enlarge by incorporation of adjacent parenchyma cells of the pericycle and vascular parenchyma . A feeding tube forms from stylet secretions .
R. reniformis can induce symptoms resembling those of moisture and nutrient deficiencies on above ground plant parts. Reniform nematode can causes hypertrophy in the pericycle cells of root seedlings and in the periderm cells of the roots of 4-5 week old plants . Generally root growth is reduced with limited secondary root development. It can produce root necrosis in pineapple and banana. Shoot growth suppression is observed and reduction of fruit quality in infected crops such as pineapple . Infected plants can become severely stunted and chlorotic, and may wilt. Wilting is often caused by opportunistic parasites such as the Fusarium and Verticillium wilts on cotton [10, 11]. Root decay can be caused by secondary fungi infection. Damage from R. reniformis is directly related to the number of nematodes present when the crop is planted. Variation among nematode populations, host, environmental conditions and soil types may alter the threshold or economic injury level across the geographic distribution of this nematode [3, 11].
Genetic resistance to reniform nematode has not been found in pineapple and cotton [3, 4]. Certain soybean and tomato cultivars are resistant to this nematode [2, 9]. Chemical control is one of the most common management practices against reniform nematode; nematicides prior and post planting are effective and increase yield [3, 9, 11]. Intercropping cover crops and crop rotation with resistant or non-host plants is used as a cultural practices to enhance soil physical characteristics, increase antagonistic microorganism, and reduce nematode populations to low levels prior to planting because some of them have allelopathic effects towards nematode. Rotations with species such as French marigold (Tagetes patula), Sunn hemp (Crotalaria juncea), are recommended [4, 11]. Moist fallow with weed control is also recommended to declines reniform nematode in crops like pineapple . Use of Paecilomyces lilacinus as a biocontrol agent, has been reported in Chickpea .
1. Ashraf, M.S and Khan, T.A. 2008. Biomanagement of reniform nematode, Rotylenchulus reniformis by fruit wastes and Paecilomyces lilacinus on Chickpea. World Journal of Agricultural Sciences 4 (4): 492-494.
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3. Lawrence, G.W. and McLean. 2001. Pag 42-44 In Compendium of Cotton Diseases 2ed. Kirkpatrick, T.L. and Rothrock, C.S. The American Phytopathological Society. St. Paul, Minnesota.
4. Luc, M., Sikora, R. and Bridge, J. 2005. Plant parasitic nematodes in subtropical and tropical agriculture. 2 ed. CABI Publishing. pp 38, 39, 709-720.
5. MacGowan, J.B. 1977. The reniform nematode. Nematology Circular No. 32. Fla. Dept. of Agric. & Consumer Serv. Division of Plant Industry.
6. Nyvall, R.F. 1999. Field Crop Diseases. Iowa State University Press, Ames, Iowa, p. 216, ISBN 0-585-16534-3.
7. Oteifa, Bakir A. 1970. The reniform nematode problem of Egyptian cotton production. The Journal of Parasitology 56(4): Section 2, Part 1: Supplement: Second International Congress of Parasitology, Resumes Nos. 1-702., pp. 1–389, p. 255.
8. Robinson, A.F., Inserra, R.N., Caswell-Chen, E.P., Vovlvas, N. and Troccoli, A. 1997. Rotylenchulus species: identification, distribution, host ranges, and crop plant resistance. Nematropica 27 (2): 127-180.
9. Rohrbach, K.G. and Schmitt, D.P. 1994. Reniform Nematode. Pag 53-54 In Compendium of Tropical Fruit Diseases. Ploetz, R.C., Zentmyer, G.A., Nishijima, W.T., Rohrbach, K.G. and Ohr, H.D. The American Phytopathological Society. St. Paul, Minnesota.
10. Shurtleff, M. and Averre, C.W. 2000. Diagnosis plant diseases caused by nematodes. APS Press. The American Phytopathologycal Society. St. Paul, Minnesota. pp 127–129.
- Rotylenchulus reniformis http://plpnemweb.ucdavis.edu/nemaplex/taxadata/g116s2.htm