Manganese Toxicity Effects on Visible Symptoms, Yield, Manganese Levels, and Organic Acid Levels in Tolerant and Sensitive Wheat Cultivars

Abstract

The effects of elevated plant intake of Mn were studied to determine whether an accurate and objective criterion could be found to identify wheat breeding lines possessing the Mn tolerance genotype. Seven wheat ( Triticum aestivum L.) cultivars (‘Teal’, ‘Lance’, ‘Isis’, ‘Maringa’, ‘Warigal’, ‘Carazinho’, and BH1146) were grown in solution culture at basal (0.5 mg/L) and increased (30, 60,90, and 180 mg/L) Mn concentrations in order to determine their biochemical response to Mn toxicity. The cultivars Teal and Isis had severe toxicity symptoms at 90 and 180 mg Mn/L. Carazinho and Warigal were unaffected at all Mn rates tested. Lance and Maringa were symptom free to 90 mg/L, while at this level BH1146 had easily visible symptoms. The reduction in dry matter yield was greatest for Teal and Isis and reflected the same pattern as observed with symptoms. In plant shoots, Mn levels were generally highest for those cultivars having least toxicity symptoms; Carazinho and Warigal had maximum levels approaching 4000 mg/kg dry matter. Reduction in dry matter yield of roots was not strongly correlated with Mn levels. Aconitic acid concentration in shoots of sensitive cultivars increased 14‐fold to a maximum value of about 30 mmol/kg fresh weight with 90 mg Mn/L in solution. There were smaller increases in the concentrations of malic and citric acids. The levels of these three acids did not change in the two tolerant cultivars.