Integrated soil-cotton system management enhances triacylglycerol yield and favourable fatty acid profile

Enhancement of triacylglycerol (TAG) and oleic acid accumulation in cottonseed is desirable as it is world's sixth largest source of plant oil in addition to its potential application in biofuel industry and material industry. In this two years study, economic N management technology, optimal plant density and simplified seedling raising technology were integrated to investigate the systematic advantage of integrated soil-cotton system management (ISSM1 and ISSM2) over conventional management practice (CM) on lipid and fatty acid profiles of cottonseed embryos under different soil available nutrition conditions. In cottonseed embryos, TAG constituted for 94.7% to 97.8% of the total lipids and the integrated soil-cotton system management resulted in the TAG yield and oleic acid increased by 32.5% and 4.5% in ISSM1 embryos, and by 19.8% and 3.8% in ISSM2 embryos. A high embryo weight compensates decreased TAG content resulted from increased N rate. Moreover, TAG yield was positively related to TAG accumulation rate, and the rapid TAG accumulation stage from 24 days to 35 days contributed the highest to the increased TAG accumulation rate (0.15 g-0.18 g per 100 embryos per day). Increased activities of glucose-6-phosphate and phosphatidate phosphatase were observed under ISSM1 and ISSM2, which reflect a quantity increase in carbon flux and energy production required for lipid biosynthesis. Moreover, increased phosphoenolpyruvate carboxylase not only regulates carbon partitioning but also enhances seed filling period and embryo weight. Taken our results suggest that the combination of simplified seedling raising technology, economic N management schedule and optimal plant density was capable of increasing carbon flux and energy production required for lipid biosynthesis and thus generate high levels of embryo TAG and oleic acid at different soil available nutrition conditions. Targeted improvement of cottonseed yield should not focus on TAG content alone but also embryo weight and seed filling period.