Comparison of Greenhouse and Field Rating Systems for Fusarium Crown Rot in Winter Wheat.

Fusarium crown rot (FCR) (Fusarium culmorum) is a common soil-born fungal pathogen causing an average of 9.5% wheat yield losses and economic losses of nearly $51.00 ha-1 in the Pacific Northwest United States (Smiley et al., 2005). Inconsistent results are often produced by environmental effects in field studies when screening for FCR severity, so greenhouse screening methods have been developed to reduce this variation. The main purpose of this study was to determine if greenhouse screening produces results that are similar to results from the field. 48 soft white winter wheat genotypes were selected from the 2015 Washington Statewide Winter Wheat Variety Trial. For greenhouse screening, each variety was grown in Cone-tainers, inoculated with a mix of five different isolates of F. culmorum, vernalized and grown to the boot stage. Field samples were collected from naturally infected trials at five sites. All of the genotypes in both the greenhouse and field trials were evaluated for disease severity on a 1 through 8 scale, with 1 being the most tolerant and the best linear unbiased predictions (BLUPs) for the rating was calculated for each of the two screening methods. Eyespot (Ocumacula spp.) was detected in addition to FCR in the field screening, which confounded the field samples. Our results showed that there was a range in resistance among varieties in both the field and the greenhouse, but there was not a strong correlation between BLUPs for the greenhouse and for the field. In 2016, we will screen for both FCR and Eyespot. The widespread presence of mixed infections emphasizes the need to breed for resistance to both pathogens.