Biotechnological approaches to modify rapeseed oil composition for applications in aquaculture

Over the next two decades, aquaculture is expected to contribute more to the global supply of fish for food use and thus further help to reduce global poverty and food insecurity. One major challenge for aquaculture production is a future stable, predictable and high quality feed supply. Marine oils represent 40% of today's feed, but an increased price and reduced availability is expected to cause a demand for alternative oil resources in the near future. In consequence, the use of vegetable oils as feed for farmed carnivorous cold-water fish is increasing. Although beneficial in some respects, this requires improved fatty acid composition in plants such as soybean or rapeseed to meet the nutritional demands of farmed fish. Plants might be adapted to meet these needs by the use of functional genomics. Although most genes encoding enzymes of storage lipid biosynthesis have been identified and cloned, fatty acid regulation at the molecular level is not fully understood. Potential replacement of marine resources with plant ingredients demands extensive multidisciplinary efforts. Combinations of basic understanding of gene function, transgene integration and expression, gene interactions, fatty acid metabolism in plants and animals and finally public acceptance have to be gained. Transgenic plants with increased amounts of 18:1 n-9 (oleic acid) and 18:3 n-3 (alpha-linolenic acid) fatty acids in the seed olesomes. and extensions of these into longer fatty acids (e.g. 20:5 n-3 and 22:6 n-3) using seed specific promoters would improve rapeseed (Canola) quality for use as fish feed. (C) 2003 Elsevier Science Ireland Ltd. All rights reserved.