Abstract
With the aim of devising an effective breeding method on cool tolerance in rice, the effect of individual and line selections for cool tolerance in the early segregating generations were evaluated. Line selection appeared to be more effective than individual selection. By selection for cool tolerance, both culm length and ear length were generally increased in mean values and decreased in variances, but the degrees of their responses varied considerably with the crosses tested. The modified bulk method conducted under cool water irrigation is recommended as the most efficient breeding method for cool tolerance.
