Develolpment of a rapid screening method for Mn2+ tolerance in barley

TITLE: Develolpment of a rapid screening method for Mn2+ tolerance in barley ABSTRACT: Soil waterlogging causes reduction of oxidized ions including Mn4+, enhancing the concentration of Mn2+ which can be toxic to plant. Barley varieties showed differences in tolerance to Mn2+ toxicity, suggesting that waterlogging stress tolerance in this species may be conferred by the differences in elemental toxicity tolerance. This opens additional and largely unexplored avenues for breeding plants for waterlogging stress tolerance. To make the breeding process efficient, a rapid and robust screening tool is needed. In this study, a rapid screening protocol for Mn2+ tolerance in barley was developed using two varieties varying in waterlogging tolerance. Further twenty barley genotypes were used to validate the protocol. Ten days of 1 mM Mn2+ treatment in hydroponics resulted in a significant decline in leaf chlorophyll content. Chlorophyll contents in most waterlogging tolerant genotypes (TX, Yerong, CPI and CM72) remained at, or above, 65% of the control value. In contrast, waterlogging sensitive genotypes, Franklin and NN, showed much greater reduction in chlorophyll content, with relative SPAD value being less than 15% of the controls. Mn concentrations in sensitive varieties Franklin and Gairdner leaves were also up to 2.3 fold higher than those in tolerant genotypes. Root growth inhibition, relative shoot dry weight and relative root dry weight did not differ significantly and thus cannot be used as selecting criteria for the tolerance to Mn2+ toxicity.