Optimal preflowering phenology of irrigated rice for high yield potential in three Asian environments: a simulation study.

One of the critical traits of rice ideotypes with an increased yield potential is the length of the period from sowing to flowering. The objective of this study was to optimize preflowering phenology of irrigated rice (a L.) for hig L.) for high yield potential in different Asian environments. A well-evaluated ecophysiological model for irrigated rice production, ORYZA1, was used in this study. This model was coupled to the 3s-Beta model for preflowering phenology that accounts for critical changes in photothermal responses of rice during ontogeny. Using a random number generator programme, 808 combinations of parameter values of the 3s-Beta model, each equivalent to a hypothetical plant type, were created. The yield potential of these plant types was estimated by ORYZA1 for three locations, representing tropical, subtropical and temperate climatic environments, respectively. For each environment there was an optimal preflowering period (PFP) that produced the highest yield. That PFP was not suitable in the subtropical and tropical environments from a cropping system viewpoint, however. In the subtropical environment, rice yield potential was restricted by the available growing season. In the tropical location, a critical flowering time was found, beyond which yield did not increase much by extending PFP. This critical value can be determined as the practically optimum PFP for the location as it allows a minimum growth duration without sacrificing yield potential. Yield was not sensitive to changes in individual phenological characteristics at the same PFP. As current standard cultivars in the different environments have a PFP that is very close to the optimum, the possibility for further improvement of yield potential by manipulating preflowering phenology is limited.