Abstract
To study whether wild rice species have genes that may increase potential photosynthetic capacities of rice cultivars, we generated BC2 populations by reciprocally backcrossing Oryza rufipogon (W630) with O. sativa cv. Nipponbare and IR36; N-BC2 populations and IR-BC2 populations, respectively. We measured the oxygen evolution rates (OER) of single leaves under saturating light and CO2 as the maximum photosynthetic rates and the contents of ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) and Rubisco activase. Several lines in each BC2 population had significantly higher OERs than parental cultivars, and 14–25% of plants in BC2 populations had higher OERs than the highest values in parental cultivars. The highest OERs in BC2 populations were about 60% higher than average OERs in parental cultivars. The BC2 populations contained 30–40% more Rubisco than parental cultivars. The Rubisco activase contents in N-BC2 populations were 15–30% lower than that in Nipponbare. Cytoplasms derived from O. rufipogon and O. sativa had different effects on the contents of Rubisco and Rubisco activase particularly in N-BC2 populations. In several lines of each BC2 population the OERs had positive correlations with the contents of Rubisco and/or Rubisco activase. These results suggest that O. rufipogon can be used as a source of germplasm to enhance the photosynthetic capacity of O. sativa.
