Concentrations of copper (Cu) in the youngest fully emerged leaves (YFEL) and grain of eight widely grown Canadian spring wheat (Triticum aestivum L.) cultivars, Biggar, Columbus, Conway, Katepwa, Laura, Oslo, Park and Roblin, were determined. Leaves were sampled at five growth stages from field plots grown in 1990 and 1991 on Cu-deficient soil or soil treated with 12.2 kg Cu ha−1 as Cu sulphate. Symptoms of Cu deficiency, mainly rolling and wilting of young leaves and twisting and terminal dieback, were noted on Katepwa, Park and Roblin at Zadok growth stage 24. Significant (P ≤ 0.01) effects on Cu concentration in the YFEL were found due to cultivar, copper treatment, year and growth stage. The Cu concentrations in Katepwa, Park and Roblin not treated with Cu ranged between 4.6 and 5.7 μg g−1 in 1990 and between 2.8 and 3.5 μg g−1 in 1991 at Zadok growth stage 22. Cultivars Biggar, Columbus, Conway, Laura and Oslo did not show symptoms of Cu deficiency and had Cu concentrations in the range of 4.6–5.4 μg g−1 in 1990 and 2.3–3.1 μg g−1 in 1991. Deficiency symptoms were observed on Katepwa and Park supplied with Cu, although concentrations of Cu in the YFEL were relatively high. Grains sampled from the tillers generally had lower Cu concentrations than those from main stems, but the magnitude of this difference varied with the year. Significant correlations were found between Cu concentrations in the YFEL and grain yield (r = 0.90* in 1990 and 0.89* in 1991) and with floret fertility (r = 0.74* in 1990 and 0.94** in 1991). These large and significant correlations confirm the important role of Cu nutritional status in influencing floret fertility and grain yield. Critical levels of Cu in the leaves needed for unlimited growth could not be defined because of year-to-year variability. In this study, Cu concentration in the YFEL was not a useful indicator of potential Cu use efficiency in different wheat cultivars. However, for individual plants under Cu-deficiency stress, Cu concentration in the YFEL was a good indicator of the grain yield potential of different cultivars. Key words:Triticum aestivum, copper, youngest fully emerged leaves, tissue analysis
