Selecting Zinc-Efficient Wheat Genotypes with High Grain Yield Using a Stress Tolerance Index

There is no reliable indicator for identifying Zn-deficiency tolerant genotypes with high grain yield. The aim of this investigation was to compare the grain yield response of 30 spring and 20 winter bread wheat (Triticum aestivum L.) genotypes to Zn fertilization under field condition and to select high grain yield Zn-deficiency tolerant genotypes using a stress tolerance indicator. The stress tolerance indicator is a stress tolerance index (STI) used to identify genotypes that produce high yields under both nonstress and stress environments. Two individual trials, each consisting of two field plot experiments, were conducted during the 2006-2007 growing season. Spring wheat genotypes (Trial 1) and winter wheat genotypes (Trial 2) were planted in two different locations. Two Zn rates, 0 and 40 kg Zn ha(-1), using ZnSO4 center dot 7H(2)O were evaluated. Grain yield varied significantly (P < 0.01) among wheat genotypes regardless of Zn treatment. Application of Zn fertilizer increased grain yield of spring wheat genotypes an average of 883 and 913 kg ha(-1) in Karaj and Isfahan locations, respectively, although considerable variation was found among genotypes in response to Zn fertilization. Zinc efficiency (ZE) significantly differed among wheat genotypes and ranged from 69% to 95% for spring wheat and from 62% to 105% for winter wheat genotypes. Most of the wheat genotypes were placed in group A (genotypes that arc not affected by stress) and D (genotypes with low yield in both stress and nonstress environments) based on the STI. The results showed that the STI could be a better selection criterion compared with ZE for identifying high-yield stress-tolerant genotypes.