FREE FATTY-ACID CONTENTS IN DEVELOPING SEED OF 3 SUMMER CULTIVARS IN ONTARIO

Field studies were conducted in 1989 and 1990 to determine the FFA lev els during seed development of three Ontario-grown canola-quality summ er rape (Brassica napus L.) cultivars, Global, Kristina and OAC Triton , to determine the relationship between FFA and brown seeds and to ass ess the effect of silique position within the raceme on FFA. Seed mass increased linearly until 44 DAF in 1989 and curvilinearly until 43 DA F in 1990. Seed oil increased until approximately 32 and 31 DAF in 198 9 and 1990, respectively. The concentration of FFA in seeds declined i n both years until oil concentration stopped increasing, suggesting th at FFA were being incorporated into triacylglycerol. During oil synthe sis total FFA per seed increased and, as oil synthesis slowed and stop ped, FFA decreased. The individual cultivars decreased FFA to differen t levels as oil synthesis slowed, with Kristina having the lowest FFA. As the crop finished ripening the FFA levels increased in Global and OAC Triton in 1989 and in all cultivars in 1990. There was a strong po sitive correlation between FFA and percent brown seed in 1990 (r = 0.6 4) and in 1991 (r = 0.88). FFA and percent brown seed were 33 and 66%, respectively, higher in seed samples from siliques located on branche s than in seed samples from siliques located on the main raceme. FFA a nd percent brown seed were higher in seed samples from siliques on tip s than in seed samples from siliques located on the basal portion of t he raceme by 137 and 142%, respectively. The results indicated that cu ltivars differed in their ability to decrease FFA during oil synthesis and a consistent rise in mg FFA kg(-1) oil occurred at the end of the seed filling period.