SELECTION FOR RESISTANCE AND TOLERANCE TO OAT MOSAIC-VIRUS AND OAT GOLDEN STRIPE VIRUS IN HEXAPLOID OATS

Coker 716, a hexaploid oat cultivar resistant to both oat mosaic virus (OMV) and oat golden stripe virus (OGSV) was crossed to three suscept ible cultivars (Brooks, Madison, and Tech) to form three individual po pulations. Individual breeding lines were derived from each cross in t he FZ generation and tested in plots consisting of equally spaced indi vidual hills in OMV-and OGSV-infested soils and non-infested soils to evaluate resistance and yield loss of individual lines. Foliar symptom s, harvest index, and yield loss were examined as selection criteria f or resistant genotypes. The study was conducted over 2 years at two No rth Carolina locations that differed in soil type and climate. Multipl e regression models describing yield loss in each cross due to rating, year, and location were calculated. Coefficients of multiple determin ation in these models ranged from 0.39 to 0.51. Yield loss ranged from 39 to 60% among different crosses. Infection by OMV and OGSV accounte d for the majority of yield loss in two of the populations. Disease se verity varied widely over years and locations. The results suggest tha t selection of lines with symptomatic tissue of 10% or less, or select ion of tolerant lines, is needed for breeding progress.