Diallel analysis for tocopherol contents in seeds of rapeseed

Because of their nutritional and antioxidative properties, tocopherol production is an interesting trait for the lipid quality of oil crops. Total tocopherol content in rapeseed (Brassica napus L.) is medium to low, and therefore, higher levels of tocopherol are desirable in this species. The objective of the present study was to determine the inheritance of alpha-, gamma-, and total tocopherol content and the alpha-/gamma -tocopherol ratio in seed of rapeseed. Two diallel mating designs with six parents each were used. In Diallel I, the parents selected were high or low for total tocopherol content and in Diallel II, the parents were high or low for the alpha-/gamma -tocopherol ratio. Parents and F-1 hybrids were tested in a screenhouse in 1998 and under field conditions in 1999 by means of a completely randomized design with two replications. In addition, 10 selected F-2 populations were grown along with their respective parents. Compared with the parents, the F-1 hybrids showed a significantly higher gamma -tocopherol content of about 6 mg kg(-1) seed for Diallel I and 24 mg kg(-1) seed for Diallel II. General combining ability effects in both diallels were highly significant (P < 0.01) and much larger than specific combining ability effects for all traits studied. Reciprocal effects were not statistically significant. gamma -Tocopherol was not correlated with alpha -tocopherol. The results indicate that tocopherol content and composition inheritances are strongly associated th additive gene action in rapeseed.