Grafting for Management of Southern Root-Knot Nematode, Meloidogyne incognita, in Watermelon

Four bottle gourd (Lagenaria siceraria) cultivars, one squash (Cucurbita moschata x C. maxima) hybrid, five wild watermelon (Citru this lanatus var. citroides) germplasm lines, and one commercial wild watermelon (C. lanatus var. citroides) cultivar were evaluated as rootstocks for cultivated watermelon (C. lanatus var. lanatus) in fields infested with the southern root-knot nematode (Meloidogyne incognita) in Charleston, SC in 2007 and 2008, and in Quincy, FL in 2008. Commercial watermelon 'Fiesta' (diploid seeded) and 'Tri-X 313' (triploid seedless) scions were grafted onto the rootstocks in 2007 and 2008, respectively. In 2007, the plants grafted on rootstock from the wild watermelon germplasm line RKVL 318 had significantly less (P < 0.05) root galling than nongrafted 'Fiesta' watermelon or plants with the squash hybrid or bottle gourd rootstocks. In 2008, 'Fiesta' plants with rootstocks from all five wild watermelon germplasm lines and the commercial watermelon rootstock had significantly less (P < 0.05) root galling than plants with the squash hybrid or bottle gourd rootstocks. Root galling of the squash hybrid and bottle gourd rootstocks was severe (78 to 99%) in both years. Root galling for nongrafted 'Fiesta' and 'Tri-X 313' watermelon was 36 and 50%, respectively. Root galling for the wild watermelon germplasm lines ranged from 11 to 34% and 36 to 44% in 2007 and 2008, respectively. Wild watermelon germplasm lines derived from C. lanatus var. citroides were identified that may be useful as resistant rootstocks for managing root-knot nematodes in watermelon.