The phenolic compounds of 15 strawberry cultivars grown in Spain were analyzed and quantified: anthocyanins (20.2-47.4 mg/100 g of fw) (cyanidin 3-glucoside and pelargonidin 3-glucoside, 3-rutinoside, and 3-malonyl glucoside), flavonols (1.5-3.4 mg/100 g of fw) (quercetin 3-glucuronide and kaempferol 3-glucoside and 3-p-coumaroyl-glucoside), proanthocyanidins (53.9-163.2 mg/100 g), p-coumaroyl-glucose (0.84-6.70 mg/100 g), ellagitannins (9.67-22.86 mg/100 g) (sanguiin H-6, lambertianin C, and galloyl bis-HHDP-glucose), and ellagic acid glycosides (0.88-2.06 mg/100 g of fw) (two ellagic acid deoxyhexosides). Proanthocyanidins, the main phenolic compounds, were characterized by phloroglucinol degradation. Their mean degree of polymerization ranged from 3.4 for cv. Chiflon to 5.8 for cv. Ventana, the average value being 4.3. The terminal unit of proanthocyanidin oligomers was always (epi)catechin (17.36-29.93%) and (epi)catechin (61.66-75.39%) or (epi)afzelechin (4.50-10.54%) as extension units. Different combinations of (epi)catechin and (epi)afzelechin were detected, and their sequence of linkage was characterized by HPLC-MS-MS. Relative percentages of dimers, trimers, tetramers, and pentamers were evaluated by the extracted ion chromatogram (EIC) analysis.

Improvement of strawberry (Fragaria 3 ananassa) fruit flavor is an important goal in breeding programs. To investigate genetic factors controlling this complex trait, a strawberry mapping population derived from genotype '1392', selected for its superior flavor, and '232' was profiled for volatile compounds over 4 years by headspace solid phase microextraction coupled to gas chromatography and mass spectrometry. More than 300 volatile compounds were detected, of which 87 were identified by comparison of mass spectrum and retention time to those of pure standards. Parental line '1392' displayed higher volatile levels than '232', and these and many other compounds with similar levels in both parents segregated in the progeny. Cluster analysis grouped the volatiles into distinct chemically related families and revealed a complex metabolic network underlying volatile production in strawberry fruit. Quantitative trait loci (QTL) detection was carried out over 3 years based on a double pseudotestcross strategy. Seventy QTLs covering 48 different volatiles were detected, with several of them being stable over time and mapped as major QTLs. Loci controlling g-decalactone and mesifurane content were mapped as qualitative traits. Using a candidate gene approach we have assigned genes that are likely responsible for several of the QTLs. As a proof of concept we show that one homoeolog of the O-methyltransferase gene (FaOMT) is the locus responsible for the natural variation of mesifurane content. Sequence analysis identified 30 bp in the promoter of this FaOMT homoeolog containing putative binding sites for basic/helix-loop-helix, MYB, and BZIP transcription factors. This polymorphism fully cosegregates with both the presence of mesifurane and the high expression of FaOMT during ripening.

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.

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Strawberry fruit quality traits can be affected by genotype–environment interactions, determining the final consumer acceptance of fruits. Trait stability under varying environments is necessary to ensure the fruit quality of strawberries selected by breeding programs. Hence, inter- and intra-annual variation of organoleptic and functional fruit quality parameters of five strawberry varieties throughout four consecutive cropping seasons was analyzed to assess their relative stability. In most varieties, organoleptic parameters showed higher inter-annual stability but greater variability throughout the season, while the reverse was true for the functional quality parameters. Relative humidity and mean and minimum temperatures partially accounted for fruit quality variation but other factors along with the genotype may also have an influence. Among the varieties, ‘Splendor’ displayed greater year-on-year stability in organoleptic parameters, and ‘Sabrina’ and Candonga® showed higher inter- and intra-annual stability on functional fruit quality, respectively. Environmental variation did not affect fruit quality parameters similarly in all strawberry varieties. In ‘Sabrina’ and Candonga® antioxidant capacity (TEAC) was greater and stable throughout the cropping season, underlining TEAC as a tool for varietal selection, and suggesting these two varieties as parents for breeding programs that seek healthy features and high-quality fruits that meet consumer demands.

The impact that future climatic conditions will have on agricultural productivity depends on the sensitivity to each environmental factor and relative changes in temperature, precipitation and UV-B radiation. The strawberry (Fragaria x ananassa) is a microclimatic crop cultivated almost worldwide and Spain is the world's second-largest strawberry producer after the USA. Strawberry production in Huelva has been affected by climate change in recent decades. Temperature and solar radiation are primary environmental factors controlling short-day strawberry plant growth and development. Temperature is a limiting factor in crop productivity. We assessed the effect of variations in temperature and solar radiation on strawberry production and crop cycle duration. The study was carried out in commercial strawberry fruit production fields in the province of Huelva (Spain's southwestern coast). Fresh plants of cv. Camarosa were cultivated from October to June. The resulting crop was recorded weekly in the production field: early and total strawberry productions (g/ plant), were recorded from January to March and from January to May, respectively. Data revealed that between early production and temperature (R 2 = 0.86) and between early production and solar radiation (R 2 = 0.73) there was a linear relationship. However, total production and temperature (R 2 = 0.69) and total production and solar radiation (R 2 = 0.69) were related by a quadratic relationship. Our estimates suggest that strawberry production could be affected by climate change. Due to the relationship between yield and temperature, and between yield and solar radiation, climate change scenarios were found to result in reductions in crop cycle duration.

BACKGROUND: Huelva (Spain) is the main region for strawberry production in Europe. Most fruit production is exported for fresh consumption to European countries, where consumers demand high fruit quality and appreciate its healthy properties. Strawberry intake is a valuable source of antioxidants compounds with important health benefits. The higher the antioxidant capacity of a cultivar, the better the enhancement of human health. OBJECTIVE: The comparative knowledge of fruit composition on antioxidant compounds and its variation along the cropping season, in ten strawberry cultivars cropped at Huelva. METHODS: Fruit yield and citric acid, ascorbic acid, total phenolics, anthocyanins content as well as antioxidant capacity of fruits were evaluated in ten strawberry cultivars at three harvesting times during the 2014 field campaign. RESULTS: Yield and fruit parameters analyzed were strongly influenced by the genotype and by the time of harvesting. Strawberry fruit quality and antioxidant properties were greater when harvested from mid-to late-season and were not associated with higher yields. CONCLUSIONS: Healthy properties of strawberry fruits depend on cultivar and harvest time. Knowledge of the nutritional properties of these strawberry cultivars might translate into benefits to growers and enhancement of health for consumers.