Environmental influence on sunflower achene growth, oil content and oil quality

Achenes of the open-pollinated sunflower cultivar Sunfola 68-2 and the hybrid Hysun-30 were sampled at seven day intervals following first anthesis in December and April plantings at Biloela Research station in Central Queensland during 1975. For both sowing times, Sunfola 68-2 had reached maximum achene dry weight, oil and linoleic acid content by 800 growing degree days (GDD) (base -1.3�C) after first anthesis and Hysun-30 by 900 GDD (base -5.g�C). The corresponding achene moisture contents were 32.1% and 34.2%, respectively. Using this information, relations were established between oil content, linoleic acid and climatic data obtained from a number of plantings made at Emerald and Biloela in Central Queensland. Although there were significant relations between oil content and temperature, other plant and environmental factors were found to be more important in the determination of the final oil content. Linoleic acid content of Sunfola 68-2 at harvest was best related to mean temperature between 300 and 800 GDD following first anthesis in the form: Y = 63.41 + 2.46X - 0.10X2 (R2 = 79.4, P < 0.01) where X is the mean temperature 300 to 800 GDD after 50% flowering. This equation explained 80% of the variation in linoleic acid content of achenes obtained from 16 independent plantings made at Biloela from 1972 to 1975, and a range of linoleic acid from 55 to 78%. Linoleic acid for Hysun-30 was significantly correlated with both average mean and mean minimum temperatures from 300 to 900 GDD after 50% flowering. The formulation of these relations and use of the findings in the early harvesting of sunflowers and in studying planting times is discussed.