Screening Durum Wheat Germplasm for Dry Growing Conditions: Morphological and Physiological Criteria
- J. M. Clarke ,
- I. Romagosa and
- R. M. DePauw
To utilize germplasm resources effectively in breeding it is necessary to characterize and evaluate genotypes for desirable traits. In the case of factors related to grain yield under drought, it must be determined whether simply measured morphological or physiological characters can be used to identify genotypes worthy of further evaluation. To that end, 4300 durum wheat (Triticum turgidum L. var. durum) genotypes were studied under rainfed conditions on a Swinton loam soil (Aridic Haploborall) at Swift Current, SK, Canada. Heading date, visual scores of leaf rolling, leaf size, glaucousness, maturity, agronomic suitability, and residual (cuticular) transpiration rate (Rt) of excised leaves were measured in 1984. Selected subsets of genotypes were studied further in 1985 through 1987. Superior agronomic score in 1984, a dry season, was most effective for selection of genotypes with high grain-yield potential in 1985 (very dry), but not in 1986 (above average precipitation). Mean yield of genotypes selected on the basis of agronomic score and on agronomic score plus heading date was 18 and 27% greater (P < 0.01), respectively, than the mean of the unselected population. Elimination of genotypes with high Rt was associated with improved yield potential in 1985, while low Rt was associated with low yield potential in 1986. Screening for Rt was not worthwhile, given that most of the high-Rt genotypes could be effectively eliminated on the basis of poor agronomic score. Glaucousness was not a useful selection criterion since ≈93% of the genotypes were glaucous. It was concluded that visual rating of germplasm collections under dry growing conditions would be an effective means of identifying genotypes worthy of further study.
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