Studies on the Seed Production of Soybean : Vm. The ability of phoosynthesis of F3 1ines having: different photosynthesis in their F2 generations

Abstract

In order to bring about improvements in the photosynthetic ability per unit leaf area of soybean varieties by means of breeding techniques, it is desirable to clarify the genetic characteristics of photosynthetic ability of soybeans and to establish the simplified method for soybean selection. So, we tested the differences in the photosynthesis among F₃ lines by using "Manshu×Harosoy" and "Norin-1×Harosoy" as samples. The results are summarized as follows : 1. A significant difference was found statistically in the net photosynthetic rate at saturated light intensity amomg F₃ lines in either case of the two crosses. 2. Correlation coefncients of F₃ progeny(mean value of respective lines) to F₂ single plants for two crosses were high for leaf thickness and fresh leaf weight per unit leaf area, but low for net photosynthesis and total N content per unit leaf area. 3. But, the majority of F₃ lines higher in photosynthetic ability were obtained from F₂ plants with higher photosynthetic ability, and vice versa, F₃ lines lower photosyntllesis were mostly derived from F₂ plants with lower photosynthetic ability. Thus the effect of the selection on the increse in photosynthetic ability was proved. 4. In the case of lines higher in photosynthesis, a saturated light intensity being higher, it was recognized that under the condition of high light intensity, the efficiency of light energy utilization can be increased. 5. Most of F₃ lines higher in photosynthetic ability showed a tendency to become higher in the total N content per unit area, in leaf thickness and in the fresh leaf weight per area. This fact can be taken up as a means of the soybean selection. techniques.