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.

Misshapen fruit represent a significant problem for strawberry (Fragaria ×ananassa Duch.) producers around the world. We investigated the effect of cultivar and different cropping practices on the productivity of strawberry plants growing in tunnels at Huelva (Spain) over three years. In the first experiment, ‘Camarosa’, ‘Ventana’, and ‘Medina’ were planted on 10 or 22 Oct. at standard (30 × 25 cm), wide (35 × 25 cm), or narrow (25 × 25 cm) spacings. In the second experiment, ‘Camarosa’ was grown in macro- or microtunnels with and without bees. There was no effect of plant density. Planting time resulted in higher early yields in ‘Ventana’ and higher misshapen fruit in ‘Camarosa’ with an early compared with a late planting. ‘Camarosa’ had the lowest yields and the highest incidence of misshapen fruit. More of the early crop was misshaped and this was related to low temperatures in the 7 weeks before harvest. Pollination reduced the incidence of misshapen fruit and increased yield. Plants grown in macrotunnels were only more productive than those grown in microtunnels when they were pollinated by bees. These results demonstrate that the productivity of strawberry plants growing in tunnels can be enhanced by the selection of the appropriate cultivar, planting date, tunnel system, and pollination protocol. The use of macrotunnels with supplementary pollination results in better economic returns by increasing yield and decreasing the incidence of misshapen fruit. In addition, in some cultivars this profit can be enhanced by early planting, which enables early arrival of fruits into the markets at better prices for growers.

Spain's Methyl Bromide (MB) Alternatives Project" has been developing/demonstrating alternative fumigants for methyl bromide on strawberry in Huelva since 1997. Here, we describe our research carried out between 2008 and 2010. In all the trials 'Camarosa' was grown under high plastic tunnels between October and the end of May every year. Field trials with the same complete randomized block design and 10-12 treatments were performed annually in two locations of Huelva ("Occifresa"-Moguer and "Cumbres Malvinas"-Palos de la Frontera.). In 2007/08 and 2008/09 the following ten treatments were applied: untreated control; MB + chloropicrin (50 : 50 w/w); sodium azide; dazomet + 1,3D(dichloropropene); 1,3D + chloropicrin (61 : 35 w/w); chloropicrin alone; DMDS (dimethyl disulphide) + chloropicrin; methyl iodide + chloropicrin (50 : 50 w/w); acrolein; and furfural. In 2009/10, non-chemical treatments (biosolarization) were included; in comparison with previous year, four additional treatments were applied: biosolarization with fresh poultry manure (25,000 kg/ha), biosolarization with Brassica pellets (2,000 kg/ha), sodium tethathiocarbamate and metam sodium shank-applied with Rotary Spader implement. Black root rot complex (Fusarium spp., Cylindrocarpon spp., Rhizoctonia spp., and Pythium spp.) and nematodes Meloidogyne hapla and Pratylenchus penetrans were the main phytosanitary problems related to the soil, and Macrophomina phaseolina was detected occasionally in the first two seasons. However, plant survival, fruit size and yields were optimal in both locations. In 2009/10 at "Occifresa"-Moguer a higher percentage of dead plants was evidenced, and at an earlier stage than the previous growing seasons, mainly caused by Macrophomina phaseolina and Fusarium oxysporum. DMDS + chloropicrin, 1,3D + chloropicrin and chloropicrin alone were as effective as MB : chloropicrin. Biosolarization with fresh chicken manure (25,000 kg/ha) showed higher production than the untreated control.