GENOTYPIC VARIABILITY IN PHYSIOLOGICAL CHARACTERS AND ITS RELATIONSHIP TO DROUGHT TOLERANCE IN DURUM WHEAT

Yield and eight other related physiological characters [photosynthetic CO2 exchange rate (CER), stomatal resistance (rs), internal CO2 concentration, water-use efficiency (WUE), chlorophyll a + b content (Chl), specific leaf weight (SLW), leaf area and shoot dry weight] were examined in 20 durum wheat (Triticum turgidum L. var. durum) genotypes grown under nonirrigated and irrigated field conditions in 1986 and 1987. Considerable genetic differences were evident for all characters under both nonirrigated and irrigated field conditions. Significant correlations between the genotype means of the 2 years and no significant genotype × irrigation interaction indicated that the genotypic rankings were generally consistent over different environments. Reduced water availability under nonirrigated conditions decreased yield, CER, shoot dry weight, leaf area, and internal CO2 concentration and increased rs. Genotypes were separated into drought-tolerant or susceptible types based on yield potential and leaf water ...