Inter-varietal variations of rutin content in common buckwheat flour (Fagopyrum esculentum Moench.)

Summary To improve the quality of buckwheat flour, we investigated the effect of the cropping season on the rutin content in various cultivars of common buckwheat (Fagopyrum esculentum Moench.). Thirty cultivars of buckwheat were grown under both long day conditions (the summer cropping) and short day conditions (the late summer cropping). The inter-varietal variations and the effect of the cropping season on the rutin content were examined. The rutin content was determined by high performance liquid chromatography (HPLC). Results show that the average rutin content in the late summer cropping was about half that of the summer cropping. There were wide inter-varietal variations of rutin content in the summer cropping. The differences in rutin content in the late summer cropping were less pronounced. Rutin content was closely correlated with the flowering period in summer (r=0.735^***). The later flowering cultivars produced a higher content of rutin than the earlier flowering cultivars in the summer cropping. The differences in the cumulative solar radiation received in the two seasons seems to be a reasonable explanation for this increase in the rutin content of the buckwheat flour. The rutin content of early flowering cultivars, which are suitable for long day conditions, is positively correlated with yield in the summer cropping. However, the rutin content in the intermediate and late summer ecotype cultivars, which are suitable for short day conditions, shows no correlation with yield in the late-summer cropping. In conclusion, there are wide inter-varietal variations of rutin content in buckwheat flour and the rutin content increases under long day conditions.