ARS | Publication request: Watermelon seedling mortality associated with Pythium aphanidermatum

Submitted to: HortScience
Publication Type: Abstract Only
Publication Acceptance Date: March 31, 2005
Publication Date: June 1, 2005
Citation: Roberts, B.W., Bruton, B.D., Edelson, J.V., Lu, W., Perkins Veazie, P.M., Shrefler, J.W., Stanghellini, M.E. 2005. Watermelon seedling mortality associated with Pythium aphanidermatum [abstract]. HortScience. 40(30):873.

Technical Abstract: Forty-one cultivars of triploid and diploid watermelons (Citrullus lanatus) were grown at Lane, Oklahoma in 2003. Seeds were placed in Jiffy-9 pellets in a greenhouse on May 21. Fields were prepared with raised beds 1 m wide covered with black plastic. Plots were 3 m wide by 15 m long, with 4 replications, arranged as a randomized complete block. Seedlings were transplanted to the field on June 4. From June 4-9, rainfall occurred 5 days. Maximum soil temperatures at 5 cm, under bare soil, from June 1 - 9 were 34, 34, 35, 26, 22, 26, 31, 29, and 32C, respectively. On June 9, 84% of the seedlings were dead. Lesions were observed on the roots and stems and isolations were made from symptomatic tissues. The predominant pathogen isolated from the seedlings was Pythium aphanidermatum. Some of the cultivars appear to have some degree of resistance to P. aphanidermatum. Mortality among the cultivars, averaged across all replications, ranged from 33% to 100%. The cultivars with the lowest mortality were "Tri-X Carousel" (33%), "Sunny" (40%), "WT-02-31" (53%), "Ole'" (58%), and "Tri-X Palomar" (68%). New seeds were seeded in the greenhouse on June 16, and transplanted to the field on June 30. The replacement seedlings were planted in the same field, in the same location as the previous plants. Maximum soil temperatures for the two week interval following the second planting ranged from 33 - 39C, with only one rain of 0.8 cm occurring 10 days after planting. There was no apparent plant loss due to P. aphidermatum in the second planting.