Low CO concentration, a key environmental factor for developing plateau adapted rapeseed.

Background: Photosynthesis is a fundamental process that underlies the formation of crop yield, wherein light serves as the driving force and carbon dioxide (CO) as the raw material. These two factors have a direct influence on the progress and efficiency of photosynthesis in crops. Rapeseed is one of the four major oilseed crops worldwide. Plateau rapeseed has now become a research hotspot. However, the lack of high-yielding rapeseed germplasm resources on the plateau and the highly efficient strategy for screening them severely affect the development of rapeseed industry in plateau.

Results: In the rapeseed experimental fields located on the plateau (Lhasa, Tibet), we measured abundant sunlight, characterized by an average daily photosynthetically active radiation (PAR) of 1413 μmol m s. In addition, the atmospheric CO concentrations range from 300 to 400 ppm, which is only two-thirds of that in the plain (Chengdu, Sichuan). We found that under different measurement conditions of light intensity and CO concentration, different rapeseed genotypes showed significant differences in leaf photosynthetic efficiency during the seedling stage. Moreover, the rapeseed materials with high photosynthetic efficiency under low CO concentrations rather than high light intensity, exhibited significant advantages in biomass, yield, and oil content when cultivated on the plateau, indicating that the CO is the key environmental factor which limited rapeseed production in plateau. Based on photosynthetic efficiency screening under low CO concentrations, six rapeseed varieties SC3, SC10, SC25, SC27, SC29 and SC37, shown significantly higher yields in plateau environment compared to local control variety were obtained. In addition, the adaptability of rapeseed to plateau was found to be related to the activities of key Calvin cycle enzymes and the accumulation of photosynthetic products.

Conclusions: This study established a screening strategy for plateau high-yielding rapeseed materials, obtained six varieties which were suitable for plateau cultivation, explored the mechanism of rapeseed response to the plateau environment, and thus provides a feasible strategy for plateau-adapted rapeseed breeding.