RELATIONSHIP OF EXCISED-LEAF WATER LOSS RATE AND YIELD OF DURUM WHEAT IN DIVERSE ENVIRONMENTS

Abstract

The rate of water loss (RWL) from excised leaves has been proposed as a screening technique to identify wheat genotypes adapted to dry growing conditions. The relationship of RWL and grain yield was studied in 100 durum wheat (Triticum turgidum L. var. durum) genotypes grown at two locations in Canada and three locations in Syria. Fifty of the genotypes were chosen on the basis of low RWL and 50 on the basis of high RWL. Growing season precipitation ranged from 73 to 356 mm. Genotypes with low RWL yielded more than those with high RWL in four of the five driest environments in nine site-years of study. Yield of the low RWL genotypes ranged from 40 to 150% greater than that of the high RWL genotypes at the four sites. The high RWL group did not yield more than the low RWL group (P < 0.05) in any of the site-years. Glaucousness confounded interpretation of the results, since the low RWL group tended to be more glaucous than the high RWL group. Separation of the genotypes into high and low glaucousness groups showed that the high group yielded more than the low group in the three driest Canadian sites and in the wettest site in Syria. Low RWL and high glaucousness were associated with delayed leaf senescence in dry environments. It was concluded that low RWL contributes to high yield under dry growing conditions, and does not exhibit a metabolic carbon cost under more favorable precipitation regimes.Key words: Cuticular transpiration, Triticum turgidum L. var. durum, glaucousness, leaf senescence