Assessment of Drought Resistance of Crop Genotypes by Means of the Water Potential Index

Abstract

ABSTRACTThe evaluation of crop genotypes for their adaptability is often performed by means of regression techniques of yields against some kind of an environmental index as independent variable. The weakness of these techniques lies in the lack of a direct assessment of a given environment by specific environmental factors. In this work, a new index, the water potential index (WPI), is suggested as a measure of the total water stress experienced by any crop in a given environment for a specific time interval. The index is derived from the integral of the course of leaf water potential over time. Its usefulness is demonstrated in evaluations of field‐grown bread wheat [Triticum aestivum (L.) em. Thell] and faba bean (Vicia faba L.) genotypes of contrasting characteristics by yield vs. WPI linear regression analysis. In these regressions, the intercept represents the “potential” yield at no stress conditions and the slope represents the “adaptability” of each genotype. It was found that the dwarf wheat cultivars Yecora and Siette Cerros exhibited higher potential yields and lower adaptability in comparison with the tall cultivar Generoso. In faba beans, the smaller the seed size of a cultivar, the lower was the potential yield and the better the adaptability. On the basis of this regression analysis, different response scenarios of hypothetical crop genotypes are described. Furthermore, the “relative adaptability” concept is presented, in which the potential yield effect is removed from the adaptability of any genotype. Examples of the use of WPI for obtaining information on the involvement of water shortage in specific growth stages of the wheat crop or for assessing the sensitivity of faba bean yield components to water shortage are presented.