Genetics of Chloride Deficiency Expression in Barley

Abstract

Greenhouse‐grown barley exhibited symptoms resembling physiological leaf spot of wheat, a symptom of chloride (Cl−) deficiency. Twenty parents of barley mapping populations were grown hydroponically and exposed to 0 or 2.8 mmol Cl−. Response to Cl− was measured as the percentage of leaf area spotted. Chloride treatment reduced leaf spotting, and barley lines differed in susceptibility. The cultivar ‘Shyri’ was highly susceptible to leaf spotting, whereas ‘Galena’ was resistant. The mapping population derived from a ‘Shyri’/‘Galena’ cross was chosen for further study. The 100 double‐haploid progeny were grown hydroponically with complete nutrient solutions containing 0 or 0.8 mmol Cl−. Measured variables included percentage of leaf area spotted, leaf nutrient concentrations, plant height, and dry‐matter yield. Control plants exhibited 60% more leaf spotting and produced 23% less dry matter than plants receiving Cl−. Leaf Cl− concentrations ranged from 0.8 g kg−1 in control plants to 7.8 g kg−1 in plants exposed to 0.8 mmol Cl−. Chloride phenotypic data were used with map and locus information to conduct a quantitative trait loci (QTL) analysis. Using MapQTL, we mapped genetic determinants of the spotting phenotype to the short arm of chromosome 6H in an autumn study. These results were not confirmed in a winter–spring study, suggesting that unidentified environmental conditions may influence the expression of the leaf‐spotting phenotype.