INTERACTION OF CULTIVAR, SEEDING DATE AND DOWNY MILDEW INFECTION ON VARIOUS AGRONOMIC CHARACTERISTICS OF BUCKWHEAT

Field studies were conducted over 5 yr to determine the effect of seeding date on agronomic characteristics and disease reaction of buckwheat (Fagopyrum esculentum Moench). Two large-seeded, mid-season buckwheat cultivars, Manor and a semi-dwarf line, G410 or G474, and a small-seeded early-maturing cultivar, CM 169, were grown at Morden and Portage la Prairie during the period 1983–1985 at early, mid- and late June or early July seeding dates. In 1986 and 1987, Manor was grown at three seeding dates, with and without a fungicide treatment to control downy mildew (Peronospora ducometi Siemaszko and Jankowska). In the 1983–1985 experiments, seed yield generally declined with delay in seeding. The smallest decline occurred in the early-maturing cultivar CM 169. From first to last seeding, yield decreases were 38, 44 and 18% for Manor, the semi-dwarf lines and CM 169, respectively. In 1985, downy mildew infection increased linearly to a small degree with delay in seeding and was negatively correlated with seed yield. However, it was considered a minor factor in the response of yield to seeding date. In 1986 and 1987, mildew infection was minimal. The fungicide treatment had no effect on seed yield. Seed yields decreased with delay in seeding as in the previous tests. It was concluded that seed yield declined markedly with delay in seeding from early to late June, more so in the later-maturing cultivars and the declines were independent of mildew infection.Key words: Buckwheat, Fagopyrum esculentum Moench., seeding date, downy mildew, Peronospora ducometi Siemaszko & Jankowska