Metabolite Quantitative Trait Loci for Flavonoids Provide New Insights into the Genetic Architecture of Strawberry (Fragaria × ananassa) Fruit Quality

Abstract

Flavonoids are products from specialized metabolism that contribute to fruit sensorial (color) and nutritional (antioxidant properties) quality. Here, using a pseudo full-sibling F1 progeny previously studied for fruit sensorial quality of cultivated strawberry (Fragaria × ananassa), we explored over two successive years the genetic architecture of flavonoid-related traits using liquid chromatography electrospray ionization tandem mass spectrometry (13 compounds including anthocyanins, flavonols, and flavan-3-ols) and colorimetric assays (anthocyanins, flavonoids, phenolics, and total antioxidant capacity (ferric reducing antioxidant power and Trolox equivalent antioxidant capacity)). Network correlation analysis highlighted the high connectivity of flavonoid compounds within each chemical class and low correlation with colorimetric traits except for anthocyanins. Mapping onto the female and male linkage maps of 152 flavonoid metabolic quantitative trait loci (mQTLs) and of 26 colorimetric QTLs indicated colocalization on few linkage groups of major flavonoid- and taste-related QTLs previously uncovered. These results pave the way for the discovery of genetic variations underlying flavonoid mQTLs and for marker-assisted selection of strawberry varieties with improved sensorial and nutritional quality.

Genetic analysis of phenylpropanoids and antioxidant capacity in strawberry fruit reveals mQTL hotspots and candidate genes

“…Thus, all QTL controlling TPC and TEAC and 84.3% of mQTL controlling individual metabolites were only detected during one of the two assessed years. Similar results were recently reported by Labadie et al 20 in a different F 1 population of octoploid strawberry, in which the authors detected low stability of QTLs for flavonoids in ripe fruits. Due to their function protecting against oxidative stress from several environmental factors (e.g.…”

“…parental lines, as high as the SD observed among the F 1 progeny (Table 1). Similarly, other studies in strawberry and tomato have reported strong environmental effects over polyphenols and antioxidant capacity 19,20,[36][37][38] . Nevertheless, 15.3% of mQTLs controlling secondary metabolite content were detected in the two assessed years.…”

“…This agrees with results in Arabidopsis and tomato where secondary metabolites showed higher heritability than primary metabolites 39,40 . Weak correlation between different flavonoids and antioxidant capacity has been recently reported in an independent study in strawberry fruit 20 . Taken together, all these data indicate that marker-assisted selection (MAS) for increasing TPC and TEAC in strawberry fruit may not be feasible, and instead, breeding strategies for antioxidant content improvement should be directed to specific metabolites with mQTLs controlling large amount of variance and stable in different years.…”

“…In strawberry, a number of studies have analyzed polyphenols levels 14,[16][17][18] ; however, the knowledge about the genetic mechanisms underlying these processes is more limited [19][20][21] . Quantitative trait loci (QTL) mapping in bi-parental populations is a method commonly used to dissect the genetic basis of agronomic traits.…”

“…To date a very limited number of studies have aimed the detection of QTLs affecting the content of bioactive and nutritional compounds in strawberry. Only very recently genomic regions affecting the quantitative variation of fruit flavonoids have been identified in the cultivated strawberry 20,21 . In those studies, the content of 13-21 polyphenol compounds was determined and QTL controlling their variation were detected.…”