Comparison of UFWC5 and Osceola White Clover for Root-Knot Nematode Resistance.

White clover (Trifolium repens L.) is a major forage crop of the southeastern USA. It is a cool season perennial legume but acts as annual in Florida. White clover is one of the most nutritious forages available and is generally mixed with grasses to increase their feed value. But there are many constraints to white clover production. Root knot nematodes (RKN) are one of the factors adversely affecting the white clover growth, stolon density, persistence, seedling vigor, nitrogen fixing ability, and phosphorus utilization. Root-knot nematodes (Meloidogyne Spp.) are endoparasites that have a diverse host range. In addition to their direct invasion, they create wounds that lead to infection by secondary pathogens. No nematicides are labeled for pastures and the cost would be prohibitive. Thus development of resistant varieties is the best solution to enhance field production and persistence. UFWC5 was recently released with improved tolerance to root knot nematodes. This research compared UFWC5 and the commercial cultivar Osceola for response to six different RKN species and/or races. Ninety-eight plants of each species were planted in Cone-tainers in a completely randomized block design. Three weeks after germination, they are inoculated with ca. 500 eggs or J2 stage larvae of each RKN species/race. Nine weeks after inoculation, data were collected for top growth, root growth, egg mass and gall ratings and egg numbers. Differences in response to all six RKN species/races were observed for egg mass and gall ratings and egg numbers with UFWC5 being lower than Osceola for all comparisons. The largest reduction in gall and egg mass ratings between Osceola and UFWC5 were observed in response to the four races of M. incognita, the species that was used in the selection process. Commercial seed of UFWC5 will be available in fall 2008.