QTL analysis for ascorbic acid content in strawberry fruit reveals a complex genetic architecture and association with GDP-L-galactose phosphorylase

Strawberry(Fragaria×ananassa)fruits are an excellent source of L-ascorbic acid(AsA),a powerful antioxidant for plants and humans.Identifying the genetic components underlying AsA accumulation is crucial for enhancing strawberry nutritional quality.Here,we unravel the genetic architecture of AsA accumulation using an F1 population derived from parental lines‘Candonga’and‘Senga Sengana’,adapted to distinct Southern and Northern European areas.To account for environmental effects,the F1 and parental lines were grown and phenotyped in five locations across Europe(France,Germany,Italy,Poland and Spain).Fruit AsA content displayed normal distribution typical of quantitative traits and ranged five-fold,with significant differences among genotypes and environments.AsA content in each country and the average in all of them was used in combination with 6,974 markers for quantitative trait locus(QTL)analysis.Environmentally stable QTLs for AsA content were detected in linkage group(LG)3A,LG 5A,LG 5B,LG 6B and LG 7C.Candidate genes were identified within stable QTL intervals and expression analysis in lines with contrasting AsA content suggested that GDP-L-Galactose Phosphorylase FaGGP(3A),and the chloroplast-located AsA transporter gene FaPHT4;4(7C)might be the underlying genetic factors for QTLs on LG 3A and 7C,respectively.We show that recessive alleles of FaGGP(3A)inherited from both parental lines increase fruit AsA content.Furthermore,expression of FaGGP(3A)was two-fold higher in lines with high AsA.Markers here identified represent a useful resource for efficient selection of new strawberry cultivars with increased AsA content.

Identification of quantitative trait loci and candidate genes for primary metabolite content in strawberry fruit

Improvement of nutritional and organoleptic quality of fruits is a key goal in current strawberry breeding programs.The ratio of sugars to acids is a determinant factor contributing to fruit liking,although different sugars and acids contribute in varying degrees to this complex trait.A segregating F1 population of 95 individuals,previously characterized for several fruit quality characters,was used to map during 2 years quantitative trait loci(QTL)for 50 primary metabolites,L-ascorbic acid(L-AA)and other related traits such as soluble solid content(SSC),titratable acidity(TA),and pH.A total of 133 mQTL were detected above the established thresholds for 44 traits.Only 12.9%of QTL were detected in the 2 years,suggesting a large environmental influence on primary metabolite content.An objective of this study was the identification of key metabolites that were associated to the overall variation in SSC and acidity.As it was observed in previous studies,a number of QTL controlling several metabolites and traits were co-located in homoeology group V(HG V).mQTL controlling a large variance in raffinose,sucrose,succinic acid,and L-AA were detected in approximate the same chromosomal regions of different homoeologous linkage groups belonging to HG V.Candidate genes for selected mQTL are proposed based on their co-localization,on the predicted function,and their differential gene expression among contrasting F1 progeny lines.RNA-seq analysis from progeny lines contrasting in L-AA content detected 826 differentially expressed genes and identified Mannose-6-phosphate isomerase,FaM6PI1,as a candidate gene contributing to natural variation in ascorbic acid in strawberry fruit.

Potential and Limits of a High-Density Hemispherical Array of Loudspeakers for Spatial Hearing and Auralization Research

A hemispherical array of 196 independent loudspeakers has been constructed for laboratory research on spatial hearing, auralization, sound-field quality and spatial audio signal processing. The array of small loudspeakers is supported by a geodesic frame with a radius is 2.4 m. With this relatively high spatial density of sound sources, spatially quantized rendering of sound fields should be viable for a variety of applications, and this paper considers the potential and limits of this approach in relation to human spatial hearing capacities. The paper also considers the combined use of multiple loudspeakers for the rendering low-frequency components of sound sources in order to extend the low-frequency response of the system.