Vertical Migration of the Rice White-Tip Nematode, Aphelenchoides Besseyi ~

Vertical Migration of the Rice White-Tip Nematode, Aphelenchoides besseyi ~ J. A. ADAMO, C. P. MADAMBA and T. A. CHEN 2 •4bstract: In the laboratory, the vertical migration of Aphelenchoides besseyi was favored by rough surfaces and an inverse water gradient. In relation to gravity, the nematode migrated down or tap equally, a circumstance suggesting that a geotaxis was not involved. Stems of rice seedlings were effective surfaces for vertical migration of nematodes only when the stems were continuously supplied with moisture. Key Words: behavior, geolaxis. The literature dealing with the rice it was an ectoparasite on rice. It has been white-tip disease and its causal organism, suggested that tile nematode does not over- Aphelenchoides besseyi Christie, was re- winter in soil (5) and is disseminated pri- cently reviewed by Ou (11) and Ichinohe marily through infested seed (7). Fukano (10). Although no work on vertical migra- (7) indicated that irrigation water contain- tion has been reported, a number of obser- ing infested seeds was a secondary means of vations indicate the importance of the nem- spread. A chemical attraction for A. besseyi atode's migratory behavior to survival, dis- to certain cultivars of young growing rice semination, and its general life pattern. plants or aqueous extracts of germinating Several factors which affect orientation seed has been demonstrated (9). The nem- and vertical migration of above-ground, atode migrates upward in moisture that plant-parasitic nematodes have been in- forms on the walls of flasks when it is reared vestigated (1, 2, 3, 9, 18). Some parasitolo- on fungi growing on steamed rice (16). We gists have studied the nature of plant sur- have also observed that worms aggregate in faces as related to the movement of animal- droplets on both covers of Petri plates and parasitic nematodes and the abiotic ecolog- on walls of culture tubes. ical factors involved in vertical migration Since A. besseyi must migrate vertically (4, 6, 12, 13). Studies on the vertical migra- to reach developing seed, we initiated in- tion of plant-parasitic forms have concen- vestigations to determine the nature of trated primarily on Aphelenchoides ritz- vertical migration and the factors that in- emabosi (Schwartz) Steiner and Buhrer and fluence this behavior. Experiments were un- Ditylenchus dipsaci (Kiihn) Filipjev. dertaken to determine the effects of mois- In the case of A. besseyi, the literature ture, texture, surface area, and gravity on clearly suggests a relationship between mi- migration of A. besseyi. gratory behavior and the overall biology of the animal. Apparently, infection of rice MATERIALS AND METHODS plants by the nematode from soil is min- Nematodes used were from cultures imal, whereas the organism was found to maintained in the laboratory on Alternaria spread via irrigation water (19). Tamara brassicae (Berk.) Sacc. grown in potato- and Kegasawa (14) reported that A. besseyi dextrose-agar (PDA). The nematodes were did not attack the young roots of rice seed- originally isolated from rice grown in lings. However, once on the rice plant, the animal was found to move from one part to Potatan, Iloilo, the Philippines. Studies another (8). Todd (15) could not find the were conducted during December, January, nematode in any tissues and concluded that and February when the normal laboratory telnperatures were 25-30 C. All experiments were conducted in the dark. Tile test struc- Received for publication 25 October 1974. 'Conducted at the Nematology Research Laboratory, Uni- tures were removed after 18-24 11 of incuba- versity of the Philippines, Los Bafios, while the senior tion, soaked in water, and the water ex- author was on sabbatical leave and on a Fulbright-Hays grant. amined for numbers of nematodes present. -~Associate Professor. Department of S~ience. Ocean County Upward migration in a moist environ- College, Toms River, New Jersey 08753; Associate Profes- sor and Chairman, Department of Zoology, University of ment: Upward migration was determined the Philippines. Los Bahos; and Professor, Department of by using capillary tubing (0.8 mm diam), Plant Biology, Rutgers, the State University of New Jersey, New Brunswick 08903. glass microscope slides (13 x 38 mm), 146 Vertical Migration/Aphelenchoides besseyi: Adamo et al. 147 wooden match sticks (2 x 2 mm), and rice the same length were used (Fig. I-F). Two seedling (Oryza sativa Linn., 'Taichung were of the same width (14-15 mm), but Native I') stems about 4 mm wide. All the one had a rough surface and the other was materials were 38 mm long. Each structure smooth. The third glass slide had a rough was placed individually and separately in surface and a narrowed width (7-8 ram). A an upright position in a Syracuse dish previ- film of moisture was provided for each ously filled with melted paraffin wax (Fig. slide by a string drawing water from a ! A-C). One ml of sterile distilled water was well. The slides were removed from the placed around each structure, and 10 hand- culture dishes, and the worms were counted picked, freshly isolated, active worms were 18 h after initiation. The experiment was added. Each treatment was replicated 10 replicated 5 times. times. The Syracuse dishes were placed in Downward migration in a film of mois- enamel pans which in turn were kept in ture: The descending behavior of the nem- large moistened plastic bags. After 20 h, the atode was determined by using a set-up structures were removed and soaked in similar to that previously described. Two water. Rice stems and match sticks were cotton strings were connected to each of teased into small pieces and soaked over- five dishes of minced culture and extended night. Nematodes isolated from each struc- downward into small wells below (Fig. 2-A). ture were counted. One well of each pair of strings was pro- Upward migration in a firm of moisture: vided with water. Each string was removed In addition to the vertical structures uti- after 24 h and soaked before the nematodes lized in the first experiment, three-ply cot- were counted. ton string (0.7 mm diam) was also included Vertical migration in relation to grav- in the next series of tests. A film of moisture i~: A pair of wells with accompanying was provided to each surface by a string cotton strings was attached directly to each serving as a wick drawing water from a culture dish containing the nematodes. One small well. A pair of capillary tubes, match well of each pair was placed above the cul- sticks, rice stems, or strings was placed in ture dish, and the other was placed below an upright position in a dish containing (Fig. 2-C). In the first treatment, only the minced nematode-fungus culture. Treat- upper wells were filled with water, whereas ments were replicated l0 times. Each struc- in the second treatment, the lower wells ture was individually provided with a small were filled. In the third treatment, both the well (Fig. l-E, 2-B). One of the wells of upper and lower wells were supplied with each pair contained 3 ml of water, and the water. No water was supplied in any well in other was empty. the last treatment. Instead, water was ap- Two other structures, glass slides and plied on the culture dishes. All treatments capillary tubes without wells, were also in- were replicated 5 times. The wells and cluded in the second experiment. Three strings were removed after 20 h and the 13 x 38 mm glass slides, provided with wells, numbers of nematodes present were de- were placed in a dish of minced culture. termined. Two of these slides had smooth surfaces, and the other was roughened with a dia- RESULTS mond pencil (Fig. l-D). One of the smooth slides was allowed to remain dry. A pair of Upward migration in a moist environ- capillary tubes, without wells, was placed in ment: Tile upward migration of A. besseyi a dish of culture. One of the tubes was half- on vertical structures from a "pool" of filled with water, and the other was dry. water and in a moist environment was Each structure was removed after 24 h, found to vary with surface conditions. The soaked, and the number of nematodes on ascent on nontextured, nonabsorbent, sur- each was determined as previously de- faces of capillary tubes or glass slides was scribed. nil. The rate of climb on rough, absorbent Surface area: A third experiment was match sticks was high although it was not conducted to determine the relationship of so on rice seedling stems exhibiting tex- surface area to numbers of nematodes tured surfaces. climbing glass slides. Three glass slides of Upward migration in a film of moisture: 148 Journal of Nematology, Volume 8, No. 2, April 1976 i Vertical Migration/Aphelenchoides besseyi: Adamo et al. 149 FIG. 2 (A-C). Arrangement of strings, wells, and cultures for vertical migratory studies on the nem- alode, Aphelenchoides besseyi. A) Set-up for descending studies. B) Position of material for ascending studies, t:) Arrangement of materials for tests involving vertical migration in relation to gravity. The vertical ascent of nematodes in a film Surface area: The number of nematodes of moisture was found to be texture de- ascending glass slides was found to vary pendent (Table 1). The upward climb of with the area of the structure (Table 2). A. besseyi on smooth surfaces, regardless of The results show that nematodes climbed moisture conditions, was almost nil. The rough-surfaced glass slides o£ wider width number of worms climbing wet and dry more effectively than smooth surfaces. More capillary tubes did not differ.

Load more