Klaus Olbricht

Diversity of aroma patterns in wild and cultivated Fragaria accessions

Plant breeders are interested in strawberry species as donors of volatile compounds in breeding programmes because of the diversity and intensity of wild strawberry aroma. Therefore, the topic of this paper is the prospective analysis of four accessions of four wild strawberry accessions in comparison to a standard cultivar of Fragaria × ananassa Duch. by using human sensory, gas chromatography mass spectrometry (GCMS) and gas chromatography–olfactometry (GCO). The wild species have higher aroma intensities compared with the cultivated one. The flavour quality differs significantly. Semiquantitative GC analysis revealed that F. × ananassa cv. ‘Elsanta’ has the lowest content of volatile compounds whereas Fragaria moschata L. ‘Cotta’ has the highest. The aroma impressions, measured by GCO, support the findings of GCMS analyses. The nasal impact frequency (NIF)-profiles of the wild types are more manifold and of higher intensities than those of the cultivated F. × ananassa cv. ‘Elsanta’ which corresponds with the overall flavour impression when tasting the fresh fruits.

Diversity of volatile patterns in sixteen Fragaria vesca L. accessions in comparison to cultivars of Fragaria ×ananassa

Fragaria vesca is the most distributed wild species in the genus Fragaria . Due to this biogeography a high diversity is to expect. During two harvest seasons sixteen accessions from different locations from the most eastern habitat at Lake Baikal in Siberia, from Middle and Southern Europe and Northern Europe with Scandinavia and Iceland were investigated as well as two of the three described North American subspecies and three F. vesca cultivars. Five very distinct European F . ×ananassa cultivars were chosen to serve as a comparison. Beside brix value and acid contents the aroma patterns including 67 volatile compounds were quantified by stir bar sorptive extraction followed by gas chromatography with mass spectrometric detection. The diversity of important volatiles of Fragaria vesca and F . ×ananassa is discussed regarding biogeography, domestication, breeding and the so-called funnel effect.

Isolation of Dihydroflavonol 4-Reductase cDNA Clones from Angelonia x angustifolia and Heterologous Expression as GST Fusion Protein in Escherichia coli

Blue Angelonia × angustifolia flowers can show spontaneous mutations resulting in white/blue and white flower colourations. In such a white line, a loss of dihydroflavonol 4-reductase (DFR) activity was observed whereas chalcone synthase and flavanone 3-hydroxylase activity remained unchanged. Thus, cloning and characterization of a DFR of Angelonia flowers was carried out for the first time. Two full length DFR cDNA clones, Ang.DFR1 and Ang.DFR2, were obtained from a diploid chimeral white/blue Angelonia × angustifolia which demonstrated a 99% identity in their translated amino acid sequence. In comparison to Ang.DFR2, Ang.DFR1 was shown to contain an extra proline in a proline-rich region at the N-terminus along with two exchanges at the amino acids 12 and 26 in the translated amino acid sequence. The recombinant Ang.DFR2 obtained by heterologous expression in yeast was functionally active catalyzing the NADPH dependent reduction of dihydroquercetin (DHQ) and dihydromyricetin (DHM) to leucocyanidin and leucomyricetin, respectively. Dihydrokaempferol (DHK) in contrast was not accepted as a substrate despite the presence of asparagine in a position assumed to determine DHK acceptance. We show that substrate acceptance testing of DFRs provides biased results for DHM conversion if products are extracted with ethyl acetate. Recombinant Ang.DFR1 was inactive and functional activity could only be restored via exchanges of the amino acids in position 12 and 26 as well as the deletion of the extra proline. E. coli transformation of the pGEX-6P-1 vector harbouring the Ang.DFR2 and heterologous expression in E. coli resulted in functionally active enzymes before and after GST tag removal. Both the GST fusion protein and purified DFR minus the GST tag could be stored at −80°C for several months without loss of enzyme activity and demonstrated identical substrate specificity as the recombinant enzyme obtained from heterologous expression in yeast.

Diversity of metabolite patterns and sensory characters in wild and cultivated strawberries 1

In breeding programs wild strawberry species are used increasingly to enhance the genetic diversity and to implement higher sensory quality. Next to Fragaria moschata L. and F. viridis Weston wild collections cultivars of Fragaria vesca L. were the standards for strawberry taste in Europe before the development of Fragaria × ananassa Duch. around 250 years ago. Therefore, the objective of this research was the evaluation of patterns of volatile organic compounds including around twenty strawberry character impact compounds evaluated for Fragaria vesca and in comparison for standard cultivars of Fragaria × ananassa. The metabolic patterns were measured using immersion-SBSE-GC-MS. Sixteen accessions of Fragaria vesca exhibit a high diversity in qualities and quantities of volatile organic compounds (VOCs). A specific fruit sampling strategy equalizes environmental caused variation and avoids misleading interpretations. The shown results are valuable for further breeding activities regarding flavor, transcriptomic analyses, studies of biochemical pathways and signaling compounds as well as marker development.

A search for the ideal flavor of strawberry - Comparison of consumer acceptance and metabolite patterns in Fragaria × ananassa Duch.

in strawberry. Despite numerous investigations of the metabolic composition of strawberries, the description of the relationship between flavor pattern and consumer acceptance is inconsistent. The aim of the present study was to correlate overall liking (acceptance), the intensity of important sensory parameters, which were evaluated by a consumer panel, and data of instrumental analyses like soluble solids content, titratable acidity and volatile organic compound patterning. The data were collected over a period of three harvest years. They are suitable to reveal the relationships and interactions between the metabolite patterns of strawberry and the sensory properties due to the use of a high diversity of the gene pool and due to a special sample preparation with representative sample sizes for both human sensory and instrumental analysis. A high genetic diversity was considered including genotypes from cultivar crossing and from wild species introgression. It was found that the volatile compounds methyl 2-methylbutanoate, (Z)-3-hexenyl acetate, linalool and decanoic acid correlate positively with the attribute ‘sweet’ and, therefore, can act as sweetness enhancers. Furthermore, compounds were identified with positive (linalool, lactones) and negative impact (some esters, furanones) on the sensory quality. From these findings, strategies towards improved, sensorially valuable strawberry cultivars with a high consumer acceptance can be deduced. The online version of this article (doi: 10.5073/JABFQ.2016.089.029) contains supplementary files .

Strawberry Accessions with Reduced Drosophila suzukii Emergence From Fruits

Drosophila suzukii is threatening soft fruit production worldwide due to the females’ ability to pierce through the intact skin of ripe fruits and lay eggs inside. Larval consumption and the associated microbial infection cause rapid fruit degradation, thus drastic yield and economic loss. Cultivars that limit the proliferation of flies may be ideal to counter this pest; however, they have not yet been developed or identified. To search for potential breeding material, we investigated the rate of adult D. suzukii emergence from individual fruits (fly emergence) of 107 accessions of Fragaria species that had been exposed to egg-laying D. suzukii females. We found significant variation in fly emergence across strawberries, which correlated with accession and fruit diameter, and to a lesser extent with the strawberry species background. We identified accessions with significantly reduced fly emergence, not explained by their fruit diameter. These accessions constitute valuable breeding material for strawberry cultivars that limit D. suzukii spread.

Great Cause—Small Effect: Undeclared Genetically Engineered Orange Petunias Harbor an Inefficient Dihydroflavonol 4-Reductase

A recall campaign for commercial, orange flowering petunia varieties in spring 2017 caused economic losses worldwide. The orange varieties were identified as undeclared genetically engineered (GE)-plants, harboring a maize dihydroflavonol 4-reductase (DFR, A1), which was used in former scientific transgenic breeding attempts to enable formation of orange pelargonidin derivatives from the precursor dihydrokaempferol (DHK) in petunia. How and when the A1 cDNA entered the commercial breeding process is unclear. We provide an in-depth analysis of three orange petunia varieties, released by breeders from three countries, with respect to their transgenic construct, transcriptomes, anthocyanin composition, and flavonoid metabolism at the level of selected enzymes and genes. The two possible sources of the A1 cDNA in the undeclared GE-petunia can be discriminated by PCR. A special version of the A1 gene, the A1 type 2 allele, is present, which includes, at the 3′-end, an additional 144 bp segment from the non-viral transposable Cin4-1 sequence, which does not add any functional advantage with respect to DFR activity. This unequivocally points at the first scientific GE-petunia from the 1980s as the A1 source, which is further underpinned e.g., by the presence of specific restriction sites, parts of the untranslated sequences, and the same arrangement of the building blocks of the transformation plasmid used. Surprisingly, however, the GE-petunia cannot be distinguished from native red and blue varieties by their ability to convert DHK in common in vitro enzyme assays, as DHK is an inadequate substrate for both the petunia and maize DFR. Recombinant maize DFR underpins the low DHK acceptance, and, thus, the strikingly limited suitability of the A1 protein for a transgenic approach for breeding pelargonidin-based flower color. The effect of single amino acid mutations on the substrate specificity of DFRs is demonstrated. Expression of the A1 gene is generally lower than the petunia DFR expression despite being under the control of the strong, constitutive p35S promoter. We show that a rare constellation in flavonoid metabolism—absence or strongly reduced activity of both flavonol synthase and B-ring hydroxylating enzymes—allows pelargonidin formation in the presence of DFRs with poor DHK acceptance.