Wednesday, November 15, 2006

Status of Greenhouse Seedling Screening for Bird Cherry-Oat Aphid Resistance in Barley.

Dolores Mornhinweg and David Porter. USDA-ARS, USDA-ARS, 1301 N. Western, Stillwater, OK 74075-2714

Bird cherry-oat aphid (BCOA), Rhopalosiphum padi (L.), has been reported to cause yield loss in small grains both through its role as an efficient vector of the PAV strain of Barley yellow dwarf virus (BYDV) and by actual feeding damage to winter and spring small grains by aviruliferous or viruliferous BCOAs.  Barleys have been reported to have BCOA resistance based on the antibiotic effect of seedlings on the aphids. Whether this antibiosis translates to resistance in terms of grain yield has yet to be shown.  Screening for BCOA resistance at the seedling stage has been difficult due to lack of visual symptoms on seedlings infested with BCOA using traditional greenhouse screening methods. A new greenhouse seedling screening technique utilizing aviruliferous BCOA was reported where BCOA resistance was determined by a visual rating of root and shoot growth of infested wheat seedlings compared to non-infested wheat seedlings.  BCOA resistance ratings assigned by this screening technique to barley did not accurately predict resistance to BCO in terms grain yield.  In this study, 78 barleys, previously determined to be antibiotic to BCOA, were screened with aviruliferous BCOA using traditional seedling screening methods under high temperature and long days and compared to non-infested controls.  Several potential resistant checks and a susceptible check were identified through these screenings.  The barley core collection was screened using this technique.