DEVELOPMENT OF A RESISTANCE TEST FOR WINTER RYE TO SNOW MOLD (MICRODOCHIUM-NIVALE) UNDER CONTROLLED ENVIRONMENT CONDITIONS IN REGARD TO FIELD INOCULATIONS

Twenty-one winter rye inbred lines (Secale cereale) were tested for re sistance to Microdochium nivale under artificial inoculation condition s in a 2-year field experiment. Significant genotypic variation was fo und for snow mold rating, plant loss rating, number of spikes, and gra in yield relative to the noninoculated plants. Heritability was highes t for snow mold rating (h2 = 0.79). The inbred lines showed a continuo us distribution of all characters assessed for both years. Genotype x year interactions were significant for most traits. A reproducible gro wth chamber test for the evaluation of inbred lines with snow mold was developed. Best results were obtained under the following conditions: (i) hardening of plants by cultivation at low temperatures prior to i noculation, (ii) inoculation at plant growth stage of advanced tilleri ng, (iii) use of actively growing mycelium from shaken liquid culture as inoculum, (iv) cold incubation at a temperature of 1-degrees-C for inoculated plants, and (v) plant recovery period after incubation for at least 1 week in the greenhouse. The length of the cold incubation p eriod of inbred lines at 1-degrees-C was only 11 days due to an incuba tion of fungal mycelium prior to inoculation and a 2-day incubation of the inoculated plants at 13-degrees-C and 100% relative humidity. For assessing the optimal length of the cold incubation period, the optim al character for disease assessment, the significance of plant recover y after cold incubation, and the correlation to field results, a recen tly developed species specific enzyme-linked immunosorbent assay (ELIS A) was used. A significant correlation between the growth chamber test and the 2-year field trial was found with 19 inbred lines for snow mo ld rating (0.51 less-than-or-equal-to r less-than-or-equal-to 0.57). T he correlation could be improved by using the ELISA (0.69 less-than-or -equal-to r less-than-or-equal-to 0.80) to evaluate disease intensity.