Effect and Reproduction of Rotylenchulus reniformis on Sweet Potato Selections.

Growth, yield, and quality of 10 sweet potato selections and reproduction of the reniform nematode, Rotylenchulus reniformis, were studied in fumigated and nonfumigated plots in a naturally infested field. Nematode reproduction on the different selections in the field was similar to that reported in the greenhouse but was not related to the effect of the nematode on yield of the different selections. Goldrush supported the least reproduction but was the most severely affected by the nematode, while Centennial supported the most reproduction but was the least affected. Although reniform nematode was not found within enlarged fleshy roots, sweet potatoes were more frequently cracked in nonfumigated plots even when nematode populations were relatively low. One selection, P-104, was resistant to cracking. Yield of all selections tested was significantly reduced when initial populations were moderate to high (1,500-10,000 nemas per 500 cm(3)). Correlations were made between nematode population parameters and growth, yield, and cracking of the sweet potatoes. The initial populations and the reproduction ratio for the last part of the growing season gave the most significant negative correlations with yield for most selections.