Departmental Bulletin Paper 栽植密度に対するダイズ品種の収量安定性に及ぼす茎伸育性の影響 : 分枝可塑性の品種間差異と,分枝伸長過程と受光態勢からみた要因解析

阿古, 達木  ,  義平, 大樹  ,  白岩, 立彦

2015/Octoberpp.17 - 38 , 2015-10 , 酪農学園大学
We studied the differences between soybean varieties in terms of yield stability, as determined by branching plasticity, due to changes in branch yield, in accordance with planting density, and the impact of stem growth habit on branching plasticity, the using one Japanese and one American cultivar of similar earliness but different stem growth habit (Yuzuru and Jack), as well as two cultivars that are near isogenic lines (NIL) with respect to stem growth habit (Harosoy-dt1 and Harosoy-Dt1). Through our investigations over a period of two years, we tried to analyze the factors behind these variations from the point of view of branching growth process and light interception characteristics. Whether looking at branch yield or total branch length, branching plasticity was higher in the two indeterminate cultivars or lines than the two determinate cultivars or lines. The difference in total branch length between the two cases derives from the mean length of each branch rather than from the number of branches. Our examination of the difference in stem growth habit, mean branch length in particular and from the point of view of the process of branching growth, revealed that it originates mainly from the difference in the amount of growth during the peak growth period from R1 (beginning of flowering) to R3 (pod setting). This difference was also associated with the fact that even between R3 and R5 (beginning of seed growth), branching growth continued with the indeterminate cultivars, while growth in the determinate cultivars had stopped. We could not clearly determine the relationship between the difference in branching growth between varieties from the R1 stage onwards and the extinction coefficient in the grain filling period. But we were able to confirm a significant negative correlation with the relative illuminance at the top of the community (40 cm). In other words, we surmise that the difference in branching plasticity of soybean varieties due to differences in stem growth habit derives from the difference in the resulting planting plasticity due to the amount of branching growth rather than from the number of generated branches.This magnitude of the resulting density of these indeterminate cultivars arises due to the advantageousness of light interception characteristics at the top of the community.

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