Submitted to: HortScience
Publication Type: Abstract Only
Publication Acceptance Date: 2/13/2007
Publication Date: 7/1/2007
Citation: Tetteh, A., Wehner, T.C., Davis, A.R. 2007. Screening the watermelon germplasm collection for resistance to powdery mildew race 2 [abstract]. HortScience. 42(4):896.
Technical Abstract: Powdery mildew is a new disease of watermelon (Citrullus lanatus (Thunb.) Matsum. & Nakai) that is caused by Podosphaera xanthii. It causes a loss in yield of about 20%. The disease can be controlled with fungicides, however, it would be more economical and environmentally safe for growers if genetic resistance could be incorporated into commercial cultivars. P. xanthii on melon has been classified into seven or more races, and race 2 appears to be causing damage to watermelons in the southeastern United States. Genetic resistance to powdery mildew has been identified in melon lines and has been introgressed into commercial varieties. The objective of this study was to screen the watermelon germplasm collection of 1,654 accessions and cultivars for resistance to powdery mildew race 2. Plants were rated for disease severity and disease incidence. The 65 most resistant and 25 most susceptible lines were retested in both greenhouse and field. Data were analyzed using analysis of variance, with means compared using LSD. Accessions for further research were chosen based on a minimum mean rating for disease severity, low variability over replications, and the few missing data points. The most resistant accessions were PI 386015, PI 189225, PI 346082, PI 482273, PI 482277, PI 582081, PI 270545 and PI 560020. The most susceptible accessions were PI 172796 and PI 269677.