Using stress tolerance indicator (STI) to select high grain yield iron-deficiency tolerant wheat genotypes in calcareous soils

Despite large variation among crop genotypes in response to Fe fertilization, there is no reliable indicator for identifying Fe-deficiency tolerant wheat genotypes with high grain yield. The aim of this investigation was to compare the grain yield response of 20 spring and 30 winter bread wheat genotypes to Fe fertilization under field conditions and to select high grain yield Fe-deficiency tolerant genotypes using a stress tolerance indicator (STI). Two individual trials, each one consisting two field plot experiments, were conducted during 2006-2007 and 2007-2008 growing seasons. Spring wheat genotypes (Trial l) and winter wheat genotypes (Trial 2) were planted at two different locations. Two Fe rates (0 and 20kg Feha⁻¹ as Fe-EDTA) were applied. Spring and winter wheat genotypes differed significantly (P <0.01) in the grain yield both with and without added Fe treatments. Application of Fe fertilizer increased grain yield of spring wheat genotypes by an average of 211 and 551kgha⁻¹ in Karaj and Isfahan locations, respectively. By Fe application, the mean grain yield of winter wheat genotypes increased 532 and 798kgha⁻¹ in Karaj and Isfahan sites, respectively. Iron efficiency (Fe-EF) significantly differed among wheat genotypes and ranged from 65% to 113% for spring wheat and from 69% to 125% for winter wheat genotypes. No significant correlation was found between Fe-EF and grain yield of spring wheat genotypes under Fe deficient conditions. For winter wheat genotypes grown in Mashhad, Fe-efficiency was not significantly correlated with the grain yield produced without added Fe treatment. The STI was significantly (P <0.01) varied among spring and winter wheat genotypes. The interaction between location and genotype had no significant effect on the STI. According to these results, the STI should be considered as an effective criterion for screening programs, if a high potential grain yield together with more stable response to Fe fertilization in different environments is desired.