SCREENING WINTER-WHEAT FOR RESISTANCE TO COTTONY SNOW MOLD UNDER CONTROLLED CONDITIONS

A screening test was developed to determine the level of resistance of winter wheat to cottony snow mold (Coprinus psychromorbidus) under controlled conditions. The best separation in disease reaction among cultivars occurred following prehardening growth for 1 wk at 20-degrees-C, hardening at 2-degrees-C for 3 wk, and inoculation and incubation with the cottony snow mold pathogen at -3-degrees-C for 9 wk. Percent survival was determined following a 3-wk recovery in the greenhouse. Extending prehardening growth to 6 wk increased the overall level of survival, but reduced the ability of the screening test to differentiate among cultivars. In general, there was a decrease in the percent survival in the 3-wk prehardening growth treatment compared with the 1- and 6-wk treatments. Percent survival and the ability to differentiate among cultivars decreased with increasing length of incubation with the cottony snow mold pathogen at -3-degrees-C. The snow mold resistance and LT50 temperatures of 24 winter wheat cultivars, Kodiak fall rye and winter triticale were determined. Winter wheat cultivars CI14106, PI186822. Sprague, M81-8661, Munstertaler, and PI172582 exhibited high percentage survival following inoculation with cottony snow mold, but all cultivars exhibited low levels of freezing resistance except Munstertaler, which exhibited an intermediate level of freezing resistance.