Evaluation of Ergot Resistance in Hard Red Spring Wheat in North Dakota.

Higher levels of ergot (Claviceps purpurea [Fr.] Tul.) were reported in North Dakota hard red spring wheat (HRSW) in 2018, leading to questions pertaining to management and cultivar resistance. To better understand pathogen and HRSW cultivar responses, greenhouse experiments were conducted from 2020 to 2021 to evaluate the aggressiveness of nine C. purpurea isolates and ergot resistance in 21 HRSW cultivars. Results from the aggressiveness assay indicated significant cultivar-by-isolate interactions for the total weight of sclerotia produced and ergot incidence. Mean data across all cultivars by isolate combinations suggested isolates CC-3 and IA-Tim were the most aggressive, and these were subsequently used in ergot resistance experiments. Results from ergot resistance screening indicated that none of the HRSW cultivars were immune to C. purpurea because all cultivars produced sclerotia. However, differences in ergot incidence, kernel incidence, aborted kernel incidence, total sclerotia weight, sclerotia length, and sclerotia width occurred among cultivars. Both 'ND-Frohberg' and 'TCG-Spitfire' had the lowest ergot incidence values and were among the lowest in total sclerotia weight. 'Waldron' and 'LCS-Trigger' had the highest ergot incidence and the highest total sclerotia weight. Given that most concerns with ergot occur postharvest, we suggest two categories to describe ergot resistance: host resistance (fate of inoculation for a stigma) and logistical resistance (size characteristics of a sclerotium that influence its ability to remain with a seed lot after harvest and cleaning). This research provides a strong foundation for our understanding of HRSW resistance to ergot that will influence variety decisions in ergot-prone areas in North Dakota.