Mapping of chromosome regions conferring boron toxicity tolerance in barley (Hordeum vulgare L.)

Boron toxicity has been recognised as an important problem limiting product ion in the low-rainfall regions of southern Australia, West Asia and North Africa. Genetic variation for boron toxicity tolerance in barley has been c haracterised but the mode of inheritance and the location of genes controll ing tolerance were not previously known. A population of 150 doubled-haploi d lines from a cross between a boron toxicity tolerant Algerian landrace, S ahara 3771, and the intolerant Australian cultivar Clipper was screened in four tolerance assays. An RFLP linkage map of the Clipper x Sahara populati on was used to identify chromosomal regions associated with boron tolerance in barley. Interval regression-mapping allowed the detection of four chrom osomal regions involved in the boron tolerance traits measured. A region on chromosome 2H was associated with leaf-symptom expression, a region on chr omosome 3H was associated with a reduction of the affect of boron toxicity on root growth suppression, a region on chromosome 6H was associated with r educed boron uptake, and a region on chromosome 4H was also associated with the control of boron uptake as well as being associated with root-length r esponse, dry matter production and symptom expression. The benefits and pot ential of marker-assisted selection for boron toxicity tolerance are discus sed.