| Abstrakt: |
Abstract: The aim of this research was to increase understanding of tuber sensory traits such as tuber color and flavor. For tuber color the focus was on tuber carotenoid content. Using metabolic engineering approaches it was discovered that it was possible to enhance considerably the amount and types of carotenoid that could accumulate in potato tubers. Transgenic lines based on three genes, the Erwinia crtb gene, encoding phytoene synthase, the Escherichia coli dxs gene encoding 1-deoxy-d-xylulose 5-phosphate synthase and the β-carotene ketolase gene (bkt1) from the unicellular green alga Haematococcus pluvialis were developed. Plastid-targeted, tuber-specific expression of each of these transgenes was achieved and each lead to modified carotenoid content in the tuber. The crtB transgenic lines contained up to six-fold higher levels of total carotenoid and also accumulated nutritionally significant levels of the pro-vitamin A carotenoid, β-carotene, a carotenoid that is not normally found in potato tubers. The transformation of Solanum tuberosum spp. phureja (Phureja) tubers with the bkt1 gene, lead to the accumulation of the carotenoid astaxanthin, which gave the tubers an orange/pink appearance. Tuber flavor studies were based on the comparison of Phureja tubers with S. tuberosum spp. tuberosum (Tuberosum) tubers, as the Phureja tubers consistently scored higher in professional sensory evaluation panels. Measurement of the major umami compounds in tubers from several cultivars of Phureja and Tuberosum, showed consistently higher levels in the Phureja tubers, and it is hypothesised that this is an important contributor to potato flavor. |
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