Screening the watermelon germplasm collection for resistance to gummy stem blight.

摘要

All available accessions from the USDA watermelon (Citrullus lanatus) germplasm collection, including C. lanatus var. citroides, were screened for resistance to gummy stem blight (Didymella bryoniae, anamorph Phoma cucurbitacearum) in experiments conducted in North Carolina, USA. The experiment was a randomized complete block with 1325 cultigens (elite cultivars, obsolete cultivars, breeding lines, and PI accessions), 2 locations (field and greenhouse), and 2 or 4 replications. Isolates used were collected from cucurbits and verified for virulence on watermelon. The most resistant cultigens were significantly better than the control, 'Charleston Gray', and the most susceptible cultigens were significantly worse. The most resistant and most susceptible cultigens were retested, along with control cultivars (including a set of cucumber cultigens with known characteristics of resistance and susceptibility) to verify their reaction. The retest was a randomized complete block with 75 (38 in 2000) cultigens, 2 locations (field and greenhouse), and 3 or 4 replications. The most resistant cultigens were PI 279461, PI 254744, PI 482379, PI 244019, PI 526233, PI 482276, PI 164248, PI 482284, PI 296332, PI 490383, PI 271771 and PI 379243. The most susceptible cultigens were PI 226445, PI 534597, PI 525084, PI 223764, PI 169286 and PI 183398.