Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/11/2013
Publication Date: 1/31/2015
Citation: Thies, J.A., Buckner, S.A., Horry, M.I., Hassell, R., Levi, A. 2015. Influence of Citrullus lanatus var. citroides rootstocks and their F1 hybrids on yield and response to root-knot nematode, Meloidogyne incognita, in grafted watermelon. HortScience. 50:9-12.
Interpretive Summary: As a result of intense cultivation of vegetable crops on limited land resources, soil-borne disease and pests have intensified in recent years, particularly after the removal of the soil fumigant methyl bromide from the market in accordance with the Montreal Protocol on Substances that Deplete the Ozone Layer and the U.S. Clean Air Act. Presently, there are no alternative fumigants that are as effective as methyl bromide in controlling major soil-borne diseases and root-knot nematodes. The practice of grafting vegetables on disease or pest resistant rootstocks as a tool for reducing damage by soil-borne disease or pests has been considered a potential alternative. In this study, ARS scientists in Charleston, South Carolina, have conducted field experiments to test wild type watermelon lines and their F1 hybrids as potential rootstocks for grafted watermelon. The wild type watermelon rootstocks and their F1 hybrids proved to be resistant to root-knot nematodes and in fields infested with this plant-parasitic pest, they produced significantly higher yield in grafted watermelon scions than commercial cucurbit rootstocks available in the market. The rootstock line and their F1 hybrids examined here should be useful for researchers and plant breeders interested in developing rootstock lines for grafted watermelon.
Technical Abstract: Southern root-knot nematodes (Meloidogyne incognita) are an important re-emerging pest of watermelon in the U.S. and worldwide. The re-emergence of root-knot nematodes (RKN) in watermelon and other cucurbits is largely due to the intensive cultivation of vegetable crops on limited agricultural lands coupled with the loss of methyl bromide for pre-plant soil fumigation, which had served as the primary method for control of root-knot nematodes and many soil-borne diseases of cucurbits and other vegetable crops for several decades. One alternative for managing RKN in watermelon is the use of resistant rootstocks for grafted watermelon. The location have developed several RKN-resistant Citrullus lanatus var. citroides lines (designated RKVL for Root-Knot Vegetable Laboratory) which have shown promise as rootstocks for grafted watermelon. In 2011 and 2012, the scientists demonstrated that F1 hybrids derived from our selected RKVL lines exhibited resistance to RKN that was equal to or greater than that of the parental RKVL lines when grown in fields highly infested with M. incognita. Among the selected lines, RKVL 318 produced high yields in both years. In 2011, although significant differences were not observed among rootstocks, the F1 hybrids produced slightly higher yields compared with the selected parental lines. In 2012, three F1 hybrids produced higher yields than the selected parents. Overall, these F1 hybrids were vigorous and should be provide useful genetic material for selection and development of robust RKN-resistant C. lanatus var. citroides rootstock lines.