Growth properties and biomass production in the hybrid Csub(4) crop Sorghum bicolor
2016
Tazoe, Y. ((Tohoku University, Sendai (Japan). Graduate School of Agricultural Science), (JST, Chiyoda-ku, Tokyo (Japan). CREST)) | Sazuka, T. | Yamaguchi, M. | Saito, C. | Ikeuchi, M. | Kanno, K. | Kojima, S. | Hirano, K. | Kitano, H. | Kasuga, S. | Endo, T. | Fukuda, H. | Makino, A.
Hybrid vigor (heterosis) has been used as a breeding technique for crop improvement to achieve enhanced biomass production, but the physiological mechanisms underlying heterosis remain poorly understood. In this study, to find a clue to the enhancement of biomass production by heterosis, we systemically evaluated the effect of heterosis on the growth rate and photosynthetic efficiency in sorghum hybrid [Sorghum bicolor (L.) Moench cv. Tentaka] and its parental lines (restorer line and maintainer line). The final biomass of Tentaka was 10-14 times greater than that of the parental lines grown in an experimental field, but the relative growth rate during the vegetative growth stage did not differ. Tentaka exhibited a relatively enlarged leaf area with lower leaf nitrogen content per leaf area (Nsub(area)). When the plants were grown hydroponically at different N levels, daily CO2 assimilation per leaf area (A) increased with Nsub(area), and the ratio of A to Nsub(area) (N-use efficiency) was higher in the plants grown at low N levels but not different between Tentaka and the parental lines. The relationships between the CO2 assimilation rate, the amounts of photosynthetic enzymes, including ribulose-1,5-bisphosphate carboxylase/oxygenase, phosphoenolpyruvate carboxylase and pyruvate phosphate dikinase, Chl and Nsub(area) did not differ between Tentaka and the parental lines. Thus, Tentaka tended to exhibit enlargement of leaf area with lower N content, leading to a higher N-use efficiency for CO2 assimilation, but the photosynthetic properties did not differ. The greater biomass in Tentaka was mainly due to the prolonged vegetative growth period.
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