Genetic Mapping of Quantitative Trait Loci for Fruit Mass, Total Soluble Solids and Susceptibility to Water Soaking in a Strawberry ( Fragaria spp.) Model Population

Abstract

The cultivated strawberry ( Fragaria  ×  ananassa Duch.) is an economically important fruit crop. Improvement of fruit quality is a major breeding objective. Although numerous quantitative trait loci (QTLs) have been identified for fruit‐related traits, less information is available on quality attributes such as fruit mass, total soluble solids (TSS) and susceptibility to water soaking (WS). The objective of our study is to identify and validate genetic regions associated with fruit mass, TSS and WS susceptibility using a model population derived from an interspecific cross between F . ×  ananassa and Fragaria chiloensis . Phenotyping was conducted in three seasons, and QTL analysis was performed using an already existing linkage map consisting of 2990 SNP markers. The introgression of the wild‐type F. chiloensis resulted in a decrease in fruit mass and an increase in fruit TSS. Annual broad‐sense heritabilities H 2 indicated that the expression of all three traits is affected by genetic but also by environmental factors ( H 2 ranging from 0.27 to 0.68). Multiple QTLs for each trait were identified, with significant QTLs explaining up to 27% of the phenotypic variation. For TSS content, QTLs on linkage group 1C, 3A and 4A; and for WS susceptibility, QTLs on linkage group 1B, 1C, 4A and 6D were stable in at least two seasons. None of the QTLs was stable for fruit mass. This study confirmed the polygenic and complex nature of fruit mass, TSS and WS susceptibility. Some regions involved in these traits could be validated in our study, thus providing useful insights for breeding of cultivars with improved fruit mass, TSS content and tolerance against WS.