REPRODUCTIVE AND DAMAGE POTENTIALS OF 2 POPULATIONS OF ROTYLENCHULUS-RENIFORMIS ON SWEET-POTATO AND RELATED COMPARISONS WITH MELOIDOGYNE-JAVANICA ON TOMATO

Two Rotylenchulus reniformis populations (North Carolina and Georgia) were compared on sweetpotato and tomato. 'Beauregard' sweetpotato and 'Better Boy' and 'Marion' tomato were excellent hosts for both R. reni formis populations. On Beauregard sweetpotato, the two populations did not differ in fecundity; however, on both tomato cultivars, the Georg ia population reproduced at a higher rate than the North Carolina popu lation (P less than or equal to 0.05). Meloidogyne javanica reproducti on was higher (P less than or equal to 0.05) on Marion than on Better Boy. Neither population of reniform nematodes suppressed shoot growth of tomato or sweetpotato at any Pi (initial population density). Both populations of R. reniformis, however, restricted storage-root growth of Beauregard sweetpotato but enhanced shoot growth. When the Georgia population was evaluated in microplots with Pi levels of 0, 20,000, or 40,000 R. reniformis/500 cm(3) soil, total fruit weights of Better Bo y tomato were not affected. In the greenhouse, Marion tomato fresh sho ot and fruit growth (weights) was suppressed by M. javanica, but Bette r Boy was not affected. Root necrosis increased linearly with Pi on Be auregard sweetpotato grown in the greenhouse and became more pronounce d as numbers of R. reniformis increased, regardless of the population. The cultivars of tomatoes evaluated were tolerant to the two populati ons of R. reniformis in a sandy soil and exhibited no root necrosis. M arion tomato was highly susceptible to M. javanica, while Better Boy w as tolerant.