From Snow Mold Severity to Yield Performance: Identifying Promising Winter Rye Accessions Through Multi-Pathogen and Multi-Trait Assessment

Snow mold is a major constraint to winter cereal production in regions with prolonged snow cover. Because the disease is caused by phylogenetically distinct pathogens with different infection strategies, resistance is commonly treated as a single trait despite limited evidence that host responses are consistent across causal agents. Sixty winter rye accessions were evaluated over two seasons under one natural infectious background and three backgrounds experimentally enriched with Microdochium nivale, Typhula incarnata, and T. ishikariensis. Mean snow mold damage (SMD) increased from 3.69 points under the natural background to 6.54–7.41 points under the three experimentally enriched backgrounds. Accession rankings for SMD differed among backgrounds: rank correlations were weak and mostly non-significant, and the accession × background interaction was significant, indicating background-dependent, possibly partly pathogen-specific responses. Post-winter regenerative capacity was more strongly associated with grain yield than disease severity, highlighting the importance of recovery after snowmelt. The Multi-Trait Genotype–Ideotype Distance Index identified accessions combining favorable disease resistance, winter hardiness, regenerative capacity, and productivity across all backgrounds, while the best-performing accessions under individual backgrounds were identified separately from SMD rankings. These findings support multi-pathogen, multi-trait evaluation for breeding winter cereals with improved adaptation to changing winter environments.