Assessment of drought resistance in pearl millet [Pennisetum americanum (L.) Leeke]. II. Estimation of genotype response to stress.

Over 50% of variation in grain yield of breeding lines under midseason and late season drought stress proved attributable to variation in yield potential and time of flowering. This finding was used to develop a drought-response index (DRI) based on residual variation in grain yield. DRI was positively correlated with yield under drought and independent of both yield potential and time to flowering. DRI in these lines under both drought treatments was unrelated to yield component structure in irrigated controls, indicating that selection for plant type under non-stressed conditions will not influence drought response. DRI was correlated with both grain number and grain yield/panicle in both stress treatments, suggesting that lines differ in ability to maintain normal grain number under stress and/or that grain yield/panicle is an important factor in response to stress. Maintenance of panicle number did not seem to be important for maintenance of yield under stress. The correlation of DRI and individual panicle yield was sufficient for the latter to serve as a selection criterion for tolerance of late season drought stress