Reniform nematode

      Renifom Nematode (Rotylenchulus reniformis, R.parvus)

:Kingdom                 Animalia Phylum                Nematoda Class                 Secernentea Order                Tylenchida Family          Hoplolaimidae Genus             Rotylenchulus Species           R. reniformis

INTRODUCTION-

Reniform nematodes in the genus Rotylenchulus are semiendoparasitic (partially inside roots) species in which the females penetrate the root cortex, establish a permanent-feeding site in the stele region of the root and become sedentary or immobile. The anterior portion (head region) of the body remains embedded in the root whereas the posterior portion (tail region) protrudes from the root surface and swells during maturation. The term reniform refers to the kidney-shaped body of the mature female.There are ten species in the genus Rotylenchulus. Rotylenchulus reniformis is the most economically important species (Robinson 1997 ) and is called the reniform nematode

DISTRIBUTION AND HOST RANGE-

Rotylenchulus reniformis is largely distributed in tropical, subtropical and warm temperate zones in South America, North America, the Caribbean Basin, Africa, southern Europe, the Middle East, Asia, Australia, and the Pacific (Ayala and Ramirez 1964). It was first found on cowpea roots in Hawaii (Linford and Oliveira 1940), and first reported as a parasite of cotton in Georgia and of tomato in Florida. Today, it is found throughout the southern United States.In Florida, reniform nematodes are especially common in the southernmost counties, Miami-Dade and Monroe, where Rockdale soils favor reniform nematode population development. Reniform nematodes are also common in the northwestern counties of Florida (Panhandle region), from Jefferson to Santa Rosa, especially in the cotton production area with heavier soils such as sandy loam, sandy clay and clay loam (Kinloch and Sprenkel 1994).At least 314 plant species can act as hosts to reniform nematodes. Among them, cotton, cowpea, soybean, pineapple, tea and various vegetables are the most common hosts. A list of hosts and nonhosts for reniform nematode was recently published by Robinson et al. (1997). Many weed and ornamental hosts to reniform nematode in Florida have been reported by Inserra et al. (1989, 1994a, b). In southern Florida, sweet potato, papaya, and several edible aroids are excellent hosts to reniform nematodes. The reniform nematode was also associated with several kinds of tropical fruit trees (McSorley 1980; McSorley et al. 1982, 1983).

LIFE CYCLE-

Eggs hatch one to two weeks after being laid. The first-stage juvenile molts within the egg, producing the second-stage juvenile (J2) that emerges from the egg. The infective stage is reached one to two weeks after hatching. Once root penetration occurs, one or two more weeks are required for females to reach maturity. The male, which remains outside of the root, can inseminate the female before female gonad maturation. Sperms are stored in the spermatheca. Soon after female gonad maturation, the eggs are fertilized with sperm, and about 60 to 200 eggs are deposited into a gelatinous matrix. Typically, there is an equal number of females and males in a population. Some populations of reniform nematodes reproduce parthenogenetically (egg production without fertilization).The life cycle of this nematode is usually shorter than three weeks, but depends on soil temperature. However, it can survive at least two years in the absence of a host in dry soil through anhydrobiosis, a survival mechanism that allows the nematode to enter an ametabolic state and live without water for extended periods of time (Radewald and Takeshita 1964).

MANAGEMENT-

No cotton or pineapple cultivars are resistant to reniform nematodes. However, cotton breeding lines tolerant of reniform nematodes have been developed. Soybean cultivars Peking, Dyer, Custer, and Pickett are highly resistant to reniform nematode (Rebois et al. 1970). Certain tomato cultivars are resistant to this nematode (Balsubramanian and Ramakrishnan 1983).rop rotation with resistant or immune plant species is recommended. These include mustard (Brassica nigra), oats, rhodesgrass (Chloris gayana), onion, sugarcane, and sun hemp (Crotalaria juncea) (Robinson et al. 1997, Caswell et al. 1991). Pineapple is rotated with sugarcane or pagolagrass in Puerto Rico (Roman 1964). Sorghum, maize and reniform nematode resistant soybeans are recommended as rotation crops for cotton (Starr and Page 1990).Currently, Hawaiian pineapple plantations manage plant-parasitic nematodes by fallowing after pineapple for six to 12 months, then fumigating before planting, and applying postplant non-fumigant nematicides (Apt and Caswell 1988). However, dry fallow may be ineffective as a means of control since this nematode can enter into anhydrobiosis in slowly drying soils and revives when environmental conditions are favorable (Apt 1976). Apt suggested that moist fallow would be more effective as a means of control. Fallow with weeds is also unfavorable because many weeds could be hosts to reniform nematodes.Areas free of reniform nematode impose regulation against this nematode. Chile and Switzerland are among the countries that have quarantine against reniform nematode. The United States, Arizona, California and New Mexico restrict possible importation of reniform nematode to protect their cotton industries. Due to this regulation, the ornamental industries of southern Florida and Hawaii must undergo extensive sanitation of their plants and facilities to be sure they are not exporting plants contaminated with reniform nematode.

http://entnemdept.ufl.edu/creatures/nematode/r_reniformis.htm