Variation for tolerance to high concentration of ferrous iron (Fe2+) in Australian hexaploid wheat

Abstract

High concentration of reduced iron (Fe2+) in waterlogged acid soils is a constraint for growing wheat in high rainfall (waterlogged-prone) areas of Western Australia. Growing crop genotypes tolerant to high Fe2+ concentrations may be desirable in such situations, but there is no knowledge about the extent of variability in Fe2+ tolerance in the wheat germplasm. A bioassay for tolerance to high concentrations of iron in wheat was developed and optimised using Siete Cerros (Fe-tolerant) and BH1146 (Fe-intolerant) as control genotypes and a range of FeSO4 concentrations (36, 313, 625, 1250, 1875, 2500 and 3125 μM Fe2+) in nutrient solution in a controlled-temperature environment. Increasing external concentration of iron decreased both shoot and root dry weight, increased shoot iron concentration and intensified the development of toxicity symptoms to a greater degree in intolerant BH1146 as compared to tolerant Siete Cerros. Increased iron supply negatively affected uptake of Ca (r = −0.41) and Mg (r = −0.40). The tolerant genotype Siete Cerros showed an improved avoidance/exclusion of high external concentration of Fe2+ compared with intolerant BH1146. The genotypic discrimination based on relative root dry weight and the development of toxicity symptoms was most pronounced at 625 μM Fe2+. This concentration was chosen for screening of 20 bread wheat and one durum genotype chosen from a preliminary screening of 94 Australian wheat genotypes. A relatively narrow but significant variation (22–38%) in terms of relative root dry weight under Fe2+ toxicity was observed among Australian advanced breeding lines and varieties. The presence of genotypic variation for Fe2+ tolerance across and within the Australian breeding programs could be exploited in a deliberate selection process to enhance Fe2+ tolerance in wheat. Durum wheat (Arrivato) and several Australian wheat varieties and advanced lines in this study were as tolerant to Fe2+ toxicity as Siete Cerros, a variety representing common parentage of iron-tolerant genotypes.