Line‐Source vs. Irrigated/Nonirrigated Treatments for Evaluation of Genotype Drought Response

The need for efficient and effective screening for drought response of crops is well recognized. The line‐source sprinkler technique used in many crop breeding programs to evaluate genotype response to drought stress has the advantage over the traditional irrigated/nonirrigated or uniform plot technique in that it creates a continuous range of moisture deficits which permit the estimation of genotype response. In situations where the response is linear, however, the line source may not provide additional information compared to that available from the uniform plot, if both techniques sample the same range of moisture deficits. Field experiments were conducted over 2 yr to compare both screening techniques for evaluating genotype response of pearl millet [ Pennisetum glaucum (L.) R. Br.] to water deficit at grain filling. The soil was an Alfisol (Udic Rhodustalf) with approximately 60 mm of plant‐available moisture. Mean grain yields for individual positions along the moisture gradient in the line source, and means over genotypes for each replicate in the uniform plot were used as independent variables (environment means) to estimate individual genotype stress response by regression. Predicted genotype grain yield at 250 g m −2 mean yield and genotype regression coefficients were compared. There were no differences in the estimated genotype grain yields at 250 g m −2 mean grain yield from the two techniques in either year. Slopes differed in only four of the 32 genotypes in 1982 and two of the eight genotypes in 1984. When genotype response to the stress gradient is linear, the simpler uniform plot technique can be used for preliminary genotype evaluation with little loss of information.