Ergot severity, ergot incidence and quality characteristics in German winter rye hybrid and population varieties

Ergot, caused by the fungus Claviceps purpurea , is a major disease in rye, leading to yield loss and contamination with ergot alkaloids that pose food safety risks. Against the background that the EU has significantly tightened the acceptable limits for ergot sclerotia since 1 July 2025 from 0.05% to 0.02% sclerotia according to the EU Commission Regulation 2021/1399, the susceptibility of varieties to ergot is becoming an increasingly important decision criterion for farmers. Therefore, the purpose of our research was to determine the influence of variety type (population, hybrid with Rfp1 (Rfp1 +) and hybrid without Rfp1 (Rfp1–) restorer gene) on variation in ergot susceptibility under conditions of natural infection. Additionally, we sought to determine whether the susceptibility to ergot of naturally infected variety types aligns with the descriptions of susceptibility published in the Descriptive List of Varieties. The dataset used is a long-term on-farm dataset, collected between 2006 and 2024, derived from the annual assessment of the processing quality of German bread cereals. We conclude that population varieties under natural infection conditions were more resistant to ergot than hybrid variety types with and without Rfp1 restorer gene. Furthermore, we show that optimising pollination through Rfp1 genes is a more effective way of minimising ergot severity and incidence in hybrid rye breeding than blending 5–10% population rye into commercial hybrid cultivars (Rfp1–). Interestingly, we could demonstrate that some Rfp1– varieties that were rated as performing worse after artificial inoculation showed significantly better resistance under natural field conditions. These results suggest amending the procedures to optimise the rating of a candidate variety's performance in this respect. Overall, our research provides new insights into the importance of variety choice as an effective tool for farmers in minimizing and managing ergot in rye cultivation.