Abstract
Yield trials of advanced lines were grown under midseason (panicle initiation to flowering) and terminal (flowering to maturity) drought stresses in the dry seasons of 1981, 1982, and 1983. Grain yield and its components were severely reduced by the terminal stress, but were little affected by the midseason drought, as there was compensation by later tillers for yield lost on the earlier shoots. The major factor determining grain yield of a genotype in both stress treatments was its time to flowering. Because of this, yield-yield component relationships under stress were a result of yield component-phenology relationships. Yield potential (measured in an irrigated treatment in the same field) was generally positively related to yield under stress, but accounted for a much smaller fraction of yield variation than time to flowering. These two factors together accounted for more than 50 percent of the total variation in grain yield under stress, suggesting that genotype drought response was a secondary rather than a primary factor in differences in yield under stress among the genotypes tested.