Identification of genomic regions associated with powdery mildew resistance in grapevine

Abstract

Vitis vinifera L. is a perennial woody vine of global importance, both in terms of economic value and geographical distribution. Over the last decade, the progressive availability of genomic data has significantly advanced research in this field, fostering the integration of molecular breeding approaches into genetic improvement programs. These strategies, based on hybridization and Marker Assisted Selection (MAS) processes, aim to identify and characterize genes involved in phenotypic traits of interest, such as apireny (seedlessness), which is particularly valued in the table grape sector, and resistance to major fungal pathogens. In production contexts such as Italy, Erysiphe necator, the causal agent of powdery mildew, causes annual production losses of between 1 % and 25 %, with significanteconomic repercussions. The objective of this study is to identify genomic regions associated with powdery mildew resistance and tosupport marker-assisted selection in grapevine breeding. A full-sib population named FS-POP was established, crossing a Hungarian cultivar showing resistance to powdery mildew (‘Terez’) and a susceptible, seedless, table grape cultivar (‘Autumn Giant’). To evaluate the segregation of the resistance/susceptibility trait in the FS-POP progenies, the genotyping and phenotyping results have been obtained. Erysiphe resistance assessments were conducted during peak disease pressure in the field, and observations included all individuals,using a susceptible cultivar as a control. Each plant was inspected for symptoms and scored according to the OIV (International Organization of Vine and Wine) descriptor lists, using the OIV455-1 (OIV, 1984) scoring scale from 1 to 9 to assess diseasesusceptibility or resistance. The phenotyping in the open field has been carried out for 3 different years. QTL mapping and GWAS analyses were performed to identify genomic regions associated with powdery mildew resistance. Preliminary analyses revealedsegregation of resistance within the population and identified genomic regions potentially associated with the trait. The objective of thisstudy is to identify genomic regions associated with powdery mildew resistance and to support marker-assisted selection in grapevine breeding.