Utilization of physiological traits as selection criteria for drought resistance of winter wheat

Scope of study. Effective genetic improvement in drought resistance of wheat requires establishment of reliable selection criteria based on known physiological responses to drought stress. Recently, leaf relative water content (RWC) was suggested as a good indicator of plant water status and was shown to be highly heritable. Genetic investigations of the relationship between RWC and grain yield were conducted to verify RWC as a possible selection criterion. Lines were selected from a wheat population (TAM W-101/Sturdy) based on yield potential under water stress. Two sets of lines were field planted under a rainshelter; while one set was subject to drought stress by excluding any water during reproductive stages, the other set was well-watered. Abscisic acid (ABA), a plant hormone, has been known for its association with plant adaptive responses to drought stress. Increased speed, accuracy and sensitivity of ABA determination in wheat tissue offered by enzyme immunoassay (EIA) may provide breeders with the opportunity to select for ABA. However, methodological research is needed to establish the most practical sample preparation method prior to EIA.;Findings and conclusions. A positive relationship was observed between grain yield and RWC during reproductive stages as high-yield selections maintained a higher RWC than low-yield selections. The same yield-RWC association was observed among random selections segregating for both traits. Path-coefficient analysis of grain yield, yield components and RWC indicated that high RWC under drought reduced the loss of spike-bearing tillers at early reproductive stages and led to greater grain filling potential during late reproductive stages. Based on these results, RWC may serve as a reliable physiological indicator of wheat genotypes possessing high yield potential under drought stress. The results of the ABA study outlined highly effective procedures which could facilitate broadscale testing of genetic materials in which endogenous ABA content is of interest.