A Procedure to Select Drought‐Tolerant Sorghum and Millet Genotypes using Canopy Temperature and Vapor Pressure Deficit1

Abstract

AbstractPlant temperatures have been identified as indicators of plant water use and yield. The purpose of this experiment was to determine the potential of using canopy temperature for selecting drought‐tolerant genotypes. In 1983, 219 sorghum [Sorghum bicolor (L.) Moench] genotypes, assembled from Purdue University, the University of Arizona, Texas A & M University, and commercial seed companies, and 42 millet [Pennisetum americanum (L.) Leeke] genotypes from the University of Arizona, the University of Nebraska, and Kansas State University, were planted under a line source irrigation system at Yuma, AZ. The soil was a Typic Calciorthid. Five common sorghum hybrids also were used as checks. In 1984 only 27 genotypes of both crops were studied. Canopy temperature of the genotypes was measured for 7 days starting 67 to 60 days after planting in 1983 and 1984, respectively. Using all the data from each crop, an overall regression of canopy minus air temperature (DT) onto the observed vapor pressure deficit (VPD) was computed. This linear regression relationship was interpreted as the general relationship between VPD and DT for a crop. Also, a linear model of individual DT on the observed VPD was computed for each genotype. This equation predicted DT (DT) at a given value of VPD for each genotype. The sensitivity of each genotype to change in VPD was obtained by regressing the observed DT on the DT from the first regression. The genotype having coefficients < 1.0 are interpreted as having lesser sensitivity to changes in VPD. The mean temperature of a genotype higher than the average mean temperature of all the genotypes is considered as warmer. Warmer genotypes and those less sensitive to changes in VPD produce viable heads furthest from an irrigation sprinkler source.