Assessing quantitative resistance of sunflower varieties to downy mildew in breeding and variety evaluation

An experimental network involving Terres Inovia, GEVES-SNES and multiple INRA teams conducted eleven trials to characterize and quantify quantitative resistance of sunflower to downy mildew. Seventeen recombinant inbred lines carrying between zero and three quantitative trait loci associated with partial resistance were challenged by five P. halstedii pathotypes (710, 704, 714, 304, 334) under controlled conditions. Despite inter-laboratory variability, the study defines a reproducible protocol for evaluating quantitative resistance throughout the variety development cycle, from initial breeding lines to post-registration assessment, supporting sustainable disease risk management in sunflower.