The influence of agricultural practices (fertilization, mulch color, early forcing, and planting date), environment (light and growing area), cultivar, and fruit order on the selected phenolic content and antioxidant activity in strawberry (Fragaria x ananassa Duch.) fruits was studied. Three different levels of fertilization were given to plants in the fertilization experiment. The lowest fertilization level increased the contents of flavonols and ellagic acid from 19 to 57%. Between cultivars, up to 4-fold differences were found in the flavonol content, and it also varied according to growing environment. Planting date in glasshouse production was important for the phenolic content, and a statistically significant interaction was found between planting date and fruit order. Fruit order caused at highest 1.5-2.0-fold differences in the contents of phenolics. Interestingly, compared with other phenolics, anthocyanins were affected differently by many factors. Thus, the findings show that minor cultivation changes can increase the content of phenolics, especially in under-glass production where conditions can be easily manipulated.

Ericaceae (the heath family) are widely distributed calcifuges inhabiting soils with inherently poor nutrient status. Ericaceae overcome nutrient limitation through symbiosis with ericoid mycorrhizal (ErM) fungi that mobilize nutrients complexed in recalcitrant organic matter. At present, recognized ErM fungi include a narrow taxonomic range within the Ascomycota, and the Sebacinales, basal Hymenomycetes with unclamped hyphae and imperforate parenthesomes. Here we describe a novel type of basidiomycetous ErM symbiosis, termed ‘sheathed ericoid mycorrhiza’, discovered in two habitats in mid-Norway as a co-dominant mycorrhizal symbiosis in Vaccinium spp. The basidiomycete forming sheathed ErM possesses clamped hyphae with perforate parenthesomes, produces 1- to 3-layer sheaths around terminal parts of hair roots and colonizes their rhizodermis intracellularly forming hyphal coils typical for ErM symbiosis. Two basidiomycetous isolates were obtained from sheathed ErM and molecular and phylogenetic tools were used to determine their identity; they were also examined for the ability to form sheathed ErM and lignocellulolytic potential. Surprisingly, ITS rDNA of both conspecific isolates failed to amplify with the most commonly used primer pairs, including ITS1 and ITS1F + ITS4. Phylogenetic analysis of nuclear LSU, SSU and 5.8S rDNA indicates that the basidiomycete occupies a long branch residing in the proximity of Trechisporales and Hymenochaetales, but lacks a clear sequence relationship (>90% similarity) to fungi currently placed in these orders. The basidiomycete formed the characteristic sheathed ErM symbiosis and enhanced growth of Vaccinium spp. in vitro, and degraded a recalcitrant aromatic substrate that was left unaltered by common ErM ascomycetes. Our findings provide coherent evidence that this hitherto undescribed basidiomycete forms a morphologically distinct ErM symbiosis that may occur at significant levels under natural conditions, yet remain undetected when subject to amplification by ‘universal’ primers. The lignocellulolytic assay suggests the basidiomycete may confer host adaptations distinct from those provisioned by the so far investigated ascomycetous ErM fungi.

The site effect of five locations from north (Stjørdal, Norway, 63 • 36 N) to south (Ancona, Italy, 43 • 31 N) was evaluated in strawberry regarding yield performance, fruit quality, length of fruit developing time from anthesis to harvest start and length of the harvest season. Cv. Elsanta was grown at all sites while cv. Korona was cultivated in north and central Europe and cv. Clery in central and south Europe. Yield was more affected by seasonal and growing conditions than by latitude. Anthesis was delayed as influenced by cultivar up to 58 days from south to north and was nearly maintained until harvest start. Duration of fruit development was negatively related to daily mean temperature and increased with higher latitude. 29-34 days were required from anthesis to harvest start for cv. Elsanta, 29-36 for cv. Korona and 27-38 for cv. Clery. Corresponding GDD values (growing degree days; 3 • C base temperature) were independent from latitude and accounted to 334-355 for cv. Elsanta, 301-385 for cv. Korona and 320-434 for cv. Clery. Daily mean temperature decreased about 2 • C from south to north during anthesis to harvest start which induced a calculated 5.2 days longer fruit development period in the north. From harvest start to harvest end, GDD values varied for all cultivars between 297-402 GDD showing no influence of the latitude. However, simple summing of GDD values do not correctly describe the time of fruit development (from anthesis to the ripe fruit) for the whole fruiting period of a plant. GDDs for individually tagged flowers increased notably from the first third to the last third of the developing period due to increasing temperature as the season proceeded. The fruit quality standards dry matter, soluble solids and titratable acidity were influenced by latitude giving northern sites in general the highest values. Fruits grown at the southern sites were redder compared to those of the north.

The effect of four different growing locations from Stjørdal, Norway (63 • 36 N) to Conthey, Switzerland (46 • 12 N) on the composition of bioactives in strawberry (Fragaria x ananassa Duch.) of three genotypes (cvs Clery, Elsanta and Korona) was evaluated. Principal component analysis (PCA) was used to characterize differences in bioactives between genotypes within a location. Despite harvest period and year-to-year effects, a clear clustering related to the effects of the cultivars was shown. Furthermore, PCA was able to separate locations within a cultivar due to differences in bioactive compounds and this effect was stronger than local variations by temporary weather changes or even year-to-year effects. As a result, the northern samples had principally lower anthocyanin amounts than the southern ones and, moreover, distribution of individual anthocyanins was different. In contrast, the content of vitamin C and the antioxidant capacity (TEAC, ORAC, total phenols) was generally increased with higher latitudes calculated on a fresh weight basis. Results of proanthocyanidins and individual polyphenols detected by high performance liquid chromatography indicated that the higher contents were mainly due to tannin-related components. For all these observations, cultivars responded in general similarly. A North-South division was identified but no clear trend towards latitude could be recorded, mainly since one major impact factor for the biosynthesis of phenolics and ascorbic acid is temperature, which is altering not only by latitude, but also by the shift of the harvest period and the current weather conditions prior to harvest. In conclusion, genetic effects were generally stronger than environmental effects.

The aim of this review is to present an outline of the physiological perspectives of beneficial antioxidant production in fruit. The drive to enhance the consumption of fruit and vegetables in the human diet is linked with positive effects of beneficial antioxidants impacting on health promotion. We briefly outline our physiological understanding of environmental processes which induce the production of reactive oxygen species and how antioxidants prevent plant cellular damage. More specifically, we describe the impact that environmental stresses, such as drought and radiation, have on the production of endogenous antioxidants and how these stresses can be incorporated into novel experimental crop growing systems to achieve high antioxidant concentrations in fruits. This includes in particular the use of irrigation application techniques and enhanced light reflectance to increase the concentrations of bioactive compounds such as ellagic acid and ascorbic acid.