Boron toxicity in barley: prospects for delivering a yield advantage

Abstract

The physiological role of boron is not clearly understood, however it has long been established that it is essential for the growth of higher plants (Aghulon 1910). Boron can be phytotoxic if present in soils at high concentrations and has been recognised as a production constraint in regions of southern Australia, West Asia and North Africa. The genetic basis of tolerance to boron toxicity has been examined in a mapping population derived from Sahara 3771 and Clipper (Jefferies et al. 1999). This study identified four significant QTL involved in aspects of boron tolerance, however subsequent validation experiments have shown modest or inconsistent improvements in grain size and yield in boron toxic environments. The current paper presents results from studies aimed at further characterising yield responses associated with Sahara derived boron tolerance alleles, and examining the basis for potential yield penalties associated with these loci. The backcross lines were evaluated in further field trials that included analysis of rooting depth and water use in the soil profile. The sizes of introgression segments derived from Sahara were determined in this germplasm, highlighting linkage problems that potentially confound any yield advantage. Recent advances in our understanding of the mechanisms of boron toxicity tolerance are considered in relation to the genetic control of the trait. A novel method of selecting for boron tolerance is presented and discussed in the context of developing breeding strategies to maximise recombination.