Screening of a pepper collection for resistance to powdery mildew caused by Leveillula taurica, a worldwide threat

International audience

English. Cultivated peppers (Capsicum annuum L.) are under constant pressure from various pathogens. Among them, the ascomycete Leveillula taurica, the causal agent of powdery mildew, is responsible for severe infections worldwide, resulting in yield losses of up to 40%. The genetic leverage contributes to the current challenge aiming to reduce the use of phytosanitary products and their impact on the environment and human health. Both monogenic and polygenic resistances to L. taurica have been described in C. annuum and related species. However, either resistance remains ineffective under heavy infection, or the genetic determinants have not been sufficiently characterized to assist breeding. Therefore, we aim to establish a catalogue of resistance loci to L. taurica. For this purpose, core collections of C. annuum containing more than 600 accessions altogether were screened in different geographical regions with artificial inoculation to increase the disease pressure. The doubledhaploid line HV12 carrying resistance QTLs and a line carrying the PMR1 resistance gene were used as controls in experiments. PMR1-carrying plants showed significant symptoms, with the presence of sporulation, while HV12 plants displayed one of the highest levels of resistance. Our results suggest that the PMR1 gene used by breeding companies is not sufficient to control the disease. The data collected were used to perform a genome-wide association study (GWAS) to help identify novel genitors for powdery mildew resistance QTLs useful for pepper breeding programs.