W-51 Root Knot Resistant Sweet Potato Germplasm1

Abstract

Abstract Root knot caused by the southern root-knot nematode (Meloidogyne incognita (Kofoid & White) Chitwood) is a serious disease of sweet potato (Ipomoea batatas (L.) Lam.) in most production areas of the U. S. and especially in the southern states (3). Considerable variation in pathogenicity of this obligate parasite on sweet potato was reported by Giamalva et al. (1) in 1963. In 1973, Martin and Birchfield (2) reported the discovery of a race of M. incognita that was highly virulent and reproduced abundantly on a sweet potato line, L4-73, that had been established as resistant to root-knot nematode populations commonly found in Louisiana. This strain of M. incognita, herein designated the “resistance breaking” (RB) race, was provided through the courtesy of Dr. W. J. Martin of the Department of Plant Pathology, Louisiana State Univ., Baton Rouge. These findings have caused considerable concern about the future of breeding for root knot resistance in sweet potato, since the existence of RB races makes the work much more difficult and complicated. A breeding line of sweet potato (W-51) was developed at the U. S. Vegetable Laboratory, in cooperation with Clemson University, that is resistant to both the common and the RB race of root-knot nematodes (M. incognita). It also carries resistance to fusarium wilt (Fusarium oxysporum f. sp. batatas (Wr.) Snyd. & Hans.) and the sweet potato flea beetle (Chaetocnema confinis Crotch.). W-51 is being released for use as a root knot resistant parent in sweet potato breeding programs.