Integration of yield and physiological traits for developing new rice varieties with higher yield potential in tropical environment

The selection of breeding lines based on the concept of an ideal plant type has been proven to be effective in increasing yield potential. However, yield is still the main determinant whether a line will become a variety for breeders. If the selection is based on yield per se, lines with ideal plant traits and with potential to express high yield under optimal crop management condition may be discarded in the breeding nursery. This study was conducted to (i) compare grain yield and yield components among three groups of rice, namely cultivars-lines from physiologists selection, breeders selection and control; (ii) identify the physiological traits responsible for the yield difference among the groups; (iii) compare the effectiveness of selection with ideal plant type-based by physiologists and yield-based by breeders in increasing rice yield and to determine whether lines with ideal plant traits have the potential to express higher yield under optimal crop management conditions. Results showed that total biomass accumulation at flowering in the lines selected by physiologists were significantly higher than those selected by breeders selection. There was no significant difference in the biomass accumulation from flowering to physiological maturity among the three groups in 2009DS and 2009WS. Significant difference in translocation of biomass accumulated before flowering to the grain was only found between the lines selected by the breeders and those from the control in 2010DS. Sink strength might be the reason responsible for the difference. The selection by physiologists based on plant traits did not increase grain yield compared with selection based on yield per se by breeders. Among all tested breeding lines, maximum yield was produced by breeders selection and minimum yield came from physiologists selection. These results suggest that selection for yield per se by breeders was more effective in increasing grain yield than selection for plant traits by physiologists, and lines with ideal plant traits did not express higher yield under optimal crop management conditions.