High boron concentrations in soil and in irrigation water reduce crop productivity in many areas of the world. Plant tolerance to boron toxicity has been identified in a range of genotypes and recent research has revealed a physiological mechanism behind this tolerance in cereals. Cultivars with high levels of expression of a gene encoding a boron-efflux transporter in roots and shoots have been reported to show tolerance to high boron in soils and in solution culture experiments conducted under controlled conditions in glasshouses and growth rooms. However, field trials of tolerant cultivars in rain-fed semi-arid environments have been disappointing with few showing even modest improvements in yield, and others showing either no effect or a decrease in yields.
