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Abstract
Gene technology and plant breeding are combining to provide powerful means for modifying the composition of oilseeds to improve their nutritional value and provide the functional properties required for various food oil applications. Major alterations in the proportions of individual fatty acids have been achieved in a range of oilseeds using conventional selection, induced mutation and, more recently, post-transcriptional gene silencing (PTGS). In particular, a number of high-oleic oils have been developed in order to provide high-stability cooking oils. These oils provide the opportunity to replace the current widespread use of saturated fats and hydrogenated oils that contribute significantly to increased risk of cardiovascular disease due to the effect of saturated and trans-fatty acids on elevating LDL cholesterol in the bloodstream. Similarly, oils with increased stearic acid content are being developed to enable the production of solid fats without the need for hydrogenation. We have recently applied hpRNA-mediated PTGS in cotton to down-regulate key fatty acid desaturase genes and develop nutritionally-improved high-oleic (HO) and high-stearic (HS) cottonseed oils (CSOs). Silencing of the ghFAD2-1 Δ12-desaturase gene raised oleic acid content from 13% to 78% and silencing of the ghSAD-1 Δ9-desaturase gene substantially increased stearic acid from the normal level of 2% to as high as 40%. Additionally, palmitic acid was significantly lowered from 26% to 15% in both HO and HS lines. Intercrossing the HS and HO lines resulted in a wide range of unique intermediate combinations of palmitic, stearic, oleic and linoleic contents. The oxidative stability, flavor characteristics and physical properties of these novel CSOs are currently being evaluated by food technologists.
Key teaching points:
• Traditional plant breeding approaches have produced some important alterations in oilseed fatty acid compositions. However, some oilseed species lack the required natural genetic variation or are not readily amenable to mutation breeding due to their complex genomic structure.
• Gene technology has provided plant breeders with powerful new tools for manipulating the composition of plant products.
• Post-transcriptional gene silencing (PTGS) has been developed to enable the expression of genes to be precisely down-regulated during oil synthesis in the developing seed.
• Gene silencing techniques are being used to alter the relative proportions of the major fatty acids present in cottonseed oil for the purpose of improving nutritional value without compromising functionality.
Key teaching points:
• Traditional plant breeding approaches have produced some important alterations in oilseed fatty acid compositions. However, some oilseed species lack the required natural genetic variation or are not readily amenable to mutation breeding due to their complex genomic structure.
• Gene technology has provided plant breeders with powerful new tools for manipulating the composition of plant products.
• Post-transcriptional gene silencing (PTGS) has been developed to enable the expression of genes to be precisely down-regulated during oil synthesis in the developing seed.
• Gene silencing techniques are being used to alter the relative proportions of the major fatty acids present in cottonseed oil for the purpose of improving nutritional value without compromising functionality.
This cottonseed oil research outlined here was sponsored by the Australian Cotton R&D Corporation (Grant No. CSP-78C).
