Reproductive and Damage Potentials of Two Populations of Rotylenchulus reniformis on Sweetpotato 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. reniformis populations. On Beauregard sweetpotato, the two populations did not differ in fecundity; however, on both tomato cultivars, the Georgia population reproduced at a higher rate than the North Carolina population (P </= 0.05). Meloidogyne javanica reproduction was higher (P </= 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 Boy tomato were not affected. In the greenhouse, Marion tomato fresh shoot and fruit growth (weights) was suppressed by M. javanica, but Better Boy was not affected. Root necrosis increased linearly with Pi on Beauregard sweetpotato grown in the greenhouse and became more pronounced as numbers of R. reniformis increased, regardless of the population. The cultivars of tomatoes evaluated were tolerant to the two populations ofR. reniformis in a sandy soil and exhibited no root necrosis. Marion tomato was highly susceptible to M. javanica, while Better Boy was tolerant.