Seed Setting and Its Spatial Characteristics in Tartary Buckwheat (Fagopyrum tataricum)

A low seed-setting rate is the main limiting factor influencing Tartary buckwheat production under high-yield cultivation conditions. To investigate the seed setting and its spatial characteristics, two Tartary buckwheat cultivars (high seed-setting rate cultivar Qianku 3; low seed-setting rate cultivar Liuku 3) were compared by a two-year field trial in 2017 and 2018. The results showed that the Tartary buckwheat underwent simultaneous flowering and fruiting. Flowers, generated from branch, were still blooming during the mature stage of grains on stem, which resulting in a greater number of flowers and grains on the branch than those on the stem at the low part of plant. The seed-setting characteristics significantly differed between two cultivars. The high seed-setting rate of Qianku 3 was 26.6% and 33.2% higher than Liuku 3 in 2017 and 2018, respectively. Meanwhile, Qianku 3 showed a higher filled grain number (157.8%) and seed-setting rate (66.4%) on branch than Liuku 3. A network analysis showed that the whole-plant seed-setting rate was positively correlated with grain number, which was closely correlated with flower number at the same position of plant. The path-coefficient analysis revealed that grains number on branches was the most dominant component (Path coefficient (P) = 2.19) of the seed-setting rate, followed by grains number on stem (P = 0.60). The grains number on branches showed the greatest positive direct effect with significant correlation (r = 0.76 and P < 0.01) on the seed-setting rate. Overall, the present study indicated that the grain number of branches may play a vital role in improving the seed-setting rate in Tartary buckwheat.