Submitted to: Onion World
Publication Type: Trade Journal
Publication Acceptance Date: February 4, 2013
Publication Date: February 15, 2013
Citation: Havey, M.J., Cramer, C., Pappu, H., Schwartz, H. 2013. Onions showing reduced damage by thrips and iris yellow spot virus. Onion World. 29(2):14.
The goals of a USDA SCRI project were to understand better the epidemiology of the virus and to identify onion populations that suffer less damage under severe pressure from thrips and IYSV. Research demonstrated that North American isolates of IYSV were not all identical, indicating that the virus does not trace back to a single introduction. The virus can survive in many wild and cultivated plants, and its outbreak across North America is associated with increased pressure from the thrips vector. From 2009 through 2012, diverse accessions from the USDA onion germplasm collection, as well as commercial cultivars and elite breeding lines, were evaluated for damage by thrips and IYSV in field trials in Colorado and New Mexico. Better performing onions were identified and included USDA plant introductions 258956, 264320, 546140, 546188, and 546192. Many of these best performing onions possess semi-glossy foliage, due to less accumulation of epicuticular waxes on leaves, causing slower build-up of thrips and reduced spread of IYSV. Although semi-glossy foliage does not condition resistance to IYSV and thrips, its deployment represents part of an integrated approach to reduce losses by these pests. Molecular tags associated with semi-glossy foliage have been identified and these markers are being used to transfer this important avoidance mechanism into elite onions for commercial production.