Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/17/2010
Publication Date: 10/1/2010
Citation: Thies, J.A., Ariss, J.J., Hassell, R.L., Olsen, S., Kousik, C.S., Levi, A. 2010. Grafting for Management of Southern Root-knot Nematode, Meloidogyne Incognita, in Watermelon. Plant Disease. 94(10):1195-1199. Interpretive Summary: Root-knot nematodes cause extensive damage to the root systems of cucurbit crops (watermelon, melon, squash and pumpkin) which result in significant yield losses. Soil fumigation with methyl bromide has been considered the most effective treatment to control root-knot nematodes. However, methyl bromide is being banned in the United States and there is an urgent need to develop alternative agronomic methods that are effective in combating root-knot nematodes. Grafting of watermelon and melon cultivars onto cucurbit rootstocks resistant to nematodes has been considered a practical alternative for methyl bromide treatment. In this study, we conducted field tests in South Carolina and North Florida to evaluate commercial and wild cucurbit accessions for resistance to root-knot nematodes. We identified several wild watermelon accessions that are resistant to root-knot nematodes. The information in this study should be useful to plant breeders interested in developing rootstocks for watermelon. It should also be useful to watermelon growers looking for alternatives to methyl bromide for controlling root-knot nematodes.
Technical Abstract: Four bottlegourd (Lagenaria siceraria) cultivars, one squash (Cucurbita moschata x C. maxima) hybrid, four wild watermelon (Citrullus 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 with rootstocks of the wild watermelon germplasm lines and the commercial wild watermelon had significantly less (P<0.05) root galling than non-grafted ‘Fiesta’ watermelon, and plants with the squash hybrid and bottleneck gourd rootstocks. In 2008, plants with rootstocks of three wild watermelon germplasm lines had significantly less (P<0.05) root galling than non-grafted ‘Tri-X 313’ watermelon, and plants with the squash hybrid and bottleneck gourd rootstocks. Root galling of the squash hybrid and bottleneck gourd rootstocks was severe (80 to 96%) in both years. Root galling was moderately severe for non-grafted ‘Fiesta’ (40%) and non-grafted ‘Tri-X 313’ watermelon (56%). Root galling for the wild watermelon germplasm lines ranged from 11 to 34% and 32 to 42% in 2007 and 2008, respectively. Root galling of the commercial wild watermelon rootstock was 24% and 39% in 2007 and 2008, respectively. Wild watermelon germplasm lines derived from C. lanatus var. citroides may be useful as resistant rootstocks for managing root-knot nematodes in watermelon.