Exploration of a European-centered strawberry diversity panel provides markers and candidate genes for the control of fruit quality traits

Abstract

Fruit quality traits are major breeding targets in cultivated strawberry (Fragaria × ananassa). Taking into account the requirements of both growers and consumers when selecting high quality cultivars is a real challenge. Here, we used a diversity panel enriched with unique European accessions and the 50K FanaSNP array to highlight the evolution of strawberry diversity over the past 160 years, investigate the molecular basis of 12 major fruit quality traits by Genome-Wide Association Studies (GWAS), and provide genetic markers for breeding. Results show that considerable improvements of key breeding targets including fruit weight, firmness, composition and appearance occurred simultaneously in European and American cultivars. Despite the high genetic diversity of our panel, we observed a drop in nucleotide diversity in certain chromosomal regions, revealing the impact of selection. GWAS identified 71 associations with 11 quality traits and, while validating known associations (firmness, sugar), highlighted the predominance of new QTL, demonstrating the value of using untapped genetic resources. Three of the six selective sweeps detected are related to glossiness or skin resistance, two little-studied traits important for fruit attractiveness and, potentially, postharvest shelf-life. Moreover, major QTL for firmness, glossiness, skin resistance and susceptibility to bruising are found within a low diversity region of chromosome 3D. Stringent search for candidate genes underlying QTL uncovered strong candidates for fruit color, firmness, sugar and acid composition, glossiness and skin resistance. Overall, our study provides a potential avenue for extending shelf-life without compromising flavor and color as well as the genetic markers needed to achieve this goal.