Quantitative trait loci and underlying candidate genes controlling agronomical and fruit quality traits in octoploid strawberry (Fragaria × ananassa)

Abstract

Breeding for fruit quality traits in strawberry (Fragaria × ananassa, 2n = 8x = 56) is complex due to the polygenic nature of these traits and the octoploid constitution of this species. In order to improve the efficiency of genotype selection, the identification of quantitative trait loci (QTL) and associated molecular markers will constitute a valuable tool for breeding programs. However, the implementation of these markers in breeding programs depends upon the complexity and stability of QTLs across different environments. In this work, the genetic control of 17 agronomical and fruit quality traits was investigated in strawberry using a F(1) population derived from an intraspecific cross between two contrasting selection lines, '232' and '1392'. QTL analyses were performed over three successive years based on the separate parental linkage maps and a pseudo-testcross strategy. The integrated strawberry genetic map consists of 338 molecular markers covering 37 linkage groups, thus exceeding the 28 chromosomes. 33 QTLs were identified for 14 of the 17 studied traits and approximately 37% of them were stable over time. For each trait, 1-5 QTLs were identified with individual effects ranging between 9.2 and 30.5% of the phenotypic variation, indicating that all analysed traits are complex and quantitatively inherited. Many QTLs controlling correlated traits were co-located in homoeology group V, indicating linkage or pleiotropic effects of loci. Candidate genes for several QTLs controlling yield, anthocyanins, firmness and L-ascorbic acid are proposed based on both their co-localization and predicted function. We also report conserved QTLs among strawberry and other Rosaceae based on their syntenic location.

Vitamin Deficiencies in Humans: Can Plant Science Help?

“…Recently, the stable overexpression of VTC2 in tomato, strawberry, and potato succeeded in increasing fruits and tuber vitamin C by two-to sixfold (i.e., 111, 131, or 1.83 mg/100 gram fresh weight in ripe fruits of tomato, strawberry, or potato tubers, respectively) (Bulley et al, 2011). Increasing the vitamin C content by breeding is well advanced (Davey et al, 2006;Stevens et al, 2007;Zorrilla-Fontanesi et al, 2011) and will therefore be discussed below to illustrate how this strategy can be applied as an alternative to genetic engineering with regard to the other vitamins.…”

Allelic Variation in Paralogs of GDP-l-Galactose Phosphorylase Is a Major Determinant of Vitamin C Concentrations in Apple Fruit

“…Alternative biosynthetic routes involving uronic acids (Davey et al, 1999;Agius et al, 2003), L-gulose (Wolucka and Van Montagu, 2003), or myoinositol (Lorence et al, 2004) have been proposed in several plant species, including apple Razavi et al, 2005; Fig. 1), but their physiological relevance and contribution to the AsA pool is still far from clear in most plant species, with the possible exception of strawberry (Fragaria 3 ananassa; Agius et al, 2003;Cruz-Rus et al, 2011;Zorrilla-Fontanesi et al, 2011).…”

<b>Linkage disequilibrium and population structure in <i>Fragaria chiloensis</i> revealed by SSR markers transferred from commercial strawberry

“…The SSR primer pairs were selected from the first high-density SSR-based linkage map of F. × ananassa (Sargent et al, 2012). Particular interest was given to markers associated with QTL in F. × ananassa following the work of Zorrilla-Fontanesi et al (2011). Cross-species amplification of SSR markers was carried out using ten F. chiloensis accessions selected from a germplasm collection (Mora et al, 2016) according to their geographic distance ( Table 1).…”

“…We proposed that the findings of these studies should be maintained by using genome-wide co-dominant markers such as simple sequence repeats (SSR), or at least validated, as has been proven in other species such as olive (Belaj et al, 2003), maize (García et al, 2004) and Brassica napus (Li et al, 2011). In fact, SSR markers have been predominantly used in the Fragaria genus for genetic diversity studies, genetic mapping and identification of quantitative trait loci (QTL) (Sargent et al, 2012;Yoon et al, 2012;Zorrilla-Fontanesi et al, 2011). One reason that SSR markers are currently used in many species of the Fragaria genus, such as F. moschata, F. × ananassa and F. virginiana (Gil-Ariza et al, 2006) is because they represent a valuable option for the genetic evaluation of polyploid species even if they are analyzed as dominant markers.…”