Effect of geographical origin, regional adaptation, genotype, and release year on winter hardiness of wheat and triticale accessions evaluated for six decades in trials

The overwintering of accessions of three wheat species (bread, durum, spelt) and triticale was evaluated annually from 1960 to 2020 at the Crop Research Institute in Prague by means of trials in wooden-boxes. The set of tested cereal accessions was regularly changed, so that the winter survival ratings of the accessions represented a highly unbalanced set of values. Out of 15,510 winter survival values, 1,991 accessions were classified using a generalized linear model with the logit link function and transformation of calculated coefficients into a nine-point scale to estimate their genotypic Winter Hardiness Potential (WHP 1 = least hardy; WHP 9 = most hardy). The WHP of the winter wheat accessions depended on their geographical origin: for European countries, the mean ranged from WHP 7 for north-eastern countries to WHP 3 for south-western countries. There was a decrease in WHP for accessions released in the 21st century in the Central European region. A significant correlation was found between the cultivar WHPs and their survival in the field after severe winters, and registration of new, more cold tender cultivars increased after warm winters. Dependence of the overwintering index on climatic changes in the period 1960 to 2020 is discussed.