Varietal Differences of Flood Tolerance during Germination and Selection of the Tolerant Lines in Common Buckwheat

Abstract

We evaluated the varietal difference in the flood tolerance of germinated seed in 17 Japanese varieties of common buckwheat (Fagopyrum esculentum Moench), including both local varieties and bred varieties or lines of different agroecotypes. Germinated seeds were flooded for 1 day in a growth chamber in June, July and August. The mean rate of seedling emergence from the seeds sown on different dates varied with the variety ranging from 20.4 to 57.4%. The mean emergence rate of summer agroecotypes (29.9%) was significantly lower than that of intermediate and late-summer agroecotypes (42.8 and 40.1%, respectively), and that of local varieties (44.2%) was significantly higher than that of bred varieties or lines (31.2%). These results suggest that inherent variation in flood tolerance was decreased by breeding as a result of a bottleneck effect. The local variety ‘Kitou zairai’, which exhibited a high and stable seedling emergence rate, may be a suitable choice in breeding for flood tolerance during germination. We also attempted to select for flood tolerance under mild selection pressure. Mass selection after four generations increased seedling emergence rate in five of six selected lines (with the exception of ‘Kitawasesoba’) compared with those of unselected populations, although the results varied with the line. These results indicate the possibility of breeding for flood tolerance during the germination period.