Cultivar difference in grain yield and preharvest sprouting in buckwheat (Fagopyrum esculentum Moench)

We examined the grain yield, morphological characters and preharvest sprouting of the new buckwheat cultivar 'Harunoibuki' and several other cultivars. The plants were sown in April and cultivated in the southwestern region of Japan in 2004 to 2007. The grain yield of the cultivars classified as intermediate summer ecotype was higher than that of the other cultivars, and the grain yield of Harunoibuki was as high as that of intermediate summer ecotype cultivars. Flower cluster number of intermediate summer ecotype cultivars and Harunoibuki were higher than those of the summer ecotype cultivars, while the number of grain per flower cluster and individual seed weight were similar. Hitachiakisoba classified as intermediate autumn ecotype and Kanoyazairai did not mature by the end of the field experiment in July. Grain yields of Hitachiakisoba and Kanoyazairai were lower than those of other cultivars. In Hitachiakisoba and Kanoyazairai, the flower cluster number was higher, but seed setting ratio and grain number per flower cluster were lower than in other cultivars. Preharvest sprouting in Harunoibuki was significantly fewer than that in the summer ecotype and intermediate summer ecotype cultivars in all the 4 years. Year-to-year correlations of preharvest sprouting and grain yield were as high as that of plant height and seed weight, suggesting that the cultivar differences in preharvest sprouting and grain yield are consistent among years.