Productivity in Great Plains acid soils of wheat genotypes selected for aluminium tolerance

Soil acidity in the Great Plains of the USA can reduce forage and grain yields of winter wheat, primarily by Al toxicity. Indigenous cultivars may vary in seedling tolerance to Al toxicity, but the benefit that Al tolerance provides to forage and grain production is not well documented in this region. Backcrossed-derived lines of ‘Chisholm’ and ‘Century’ were selected with an additional gene from ‘Atlas 66’ conferring Al tolerance in solution culture. Our objective was to determine the impact of this source of Al tolerance on forage production prior to the jointing stage and subsequent grain yield. Experiments were conducted at several locations on non-limed (pH=4.5–4.7) and limed soils (pH=5.2-6.1) in Oklahoma. Two cultivars (‘TAM 105’, susceptible; ‘2180’, tolerant) with extreme differences in Al tolerance were used as controls . In limed conditions, forage and grain production did not differ between Al-tolerant and -susceptible genotypes, indicating a neutral effect of the Atlas 66 gene in the absence of Al toxicity. Despite visual differences in early-season plant vigor in non-limed acid soil, the Al-tolerant selections did not yield greater season-long forage than their susceptible parents. At sites where Al saturation in the non-limed soil exceeded 30%, spike production at maturity was nearly doubled in the Century background by the addition of Al tolerance, but final grain yield was not significantly improved. In the Chisholm background, grain yield was improved 50 to 74% by Al tolerance. The magnitude of the agronomic benefit of Al tolerance was highly influenced by the edaphic environment and genetic background. Acid soils of the Great Plains appear highly variable in Al toxicity; hence, consideration of the target environment is essential to predict the potential impact of Al tolerance selected in solution culture.