Submitted to: Annual Brazilian Nematology Congress Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 7/1/2003
Publication Date: N/A
Technical Abstract: Nine species of Rotylenchulus include R. anamictis, R. borealis, R. clavicaudatus, R. leptus, R. macrodoratus, R. macrosoma, R. parvus, R. reniformis, and R. sacchari. They are cosmopolitan in tropical, subtropical, and warm temperate regions but differ in thermal preferences as well as morphology, host range and presence of males. 'Reniform' (from the type species, R. reniformis) refers to the kidney shape of sedentary females. R. reniformis is most common, followed by R. borealis, R. macodoratus, R. macrosoma, and R. parvus. The life cycles of Rotylenchulus species are similar to R. reniformis. Following one molt in the egg, three superimposed molts without feeding give rise to an infective, vermiform adult with no size increase. Similar numbers of females and males are usually present but males may be rare or absent in other species. The vermiform female penetrates the root perpendicular to the stele, usually stopping to feed on a pericycle or endodermal cell. During the next two weeks, the female enlarges into a saccate form protruding from the root and lays eggs in a gelatinous matrix. A short life cycle and high density of feeding courts along roots contributes to rapid population development and high population densities. Histopathology differs among species but in all cases, the vermiform female does not migrate longitudinally within the root tissue and induces a multicellular syncytium of cells that are largely differentiated before infection. Rotylenchulus species have been studied on many crops. More than 300 plant species in 77 families are hosts. Extensive literature exists for pineapple in Hawaii, cotton and soybean in North America, and various legumes in India. Other noteworthy crops damaged or infected by Rotylenchulus spp. are cantaloupe, legumes, olive, papaya, passion fruit, pineapple, potato, sweet potato, tobacco, and tomato. Worldwide, R. reniformis appears associated with deep silty soils of volcanic or alluvial origin in river floodplains. However, the nematode also occurs at high population densities in soils of high sand or clay content. Field symptoms in cotton, soybean, and pineapple tend to be uniform and include stunting and suppressed yield. In cotton, plants show potassium deficiency symptoms. The greatest challenges to managing R. reniformis are its wide host range and ability to survive long periods without a host in dry soil. In North American cotton fields, the nematode occurs at high population densities as deep as 1 meter, hampering fumigant efficacy. Cotton roots at this dept are needed to take up water and nutrients during dry periods. Rotational crops for managing R. reniformis include barley, maize, onion, rice, peanut, Crotalaria spp. and resistant soybean. Germplasm screens to identify resistant cultivars have been conducted in blackgram, chickpea, coffee, cotton, cowpea, greengram, horsegram, olive, papaya, pepper, pigeonpea, potato and soybean.