Plant & Animal Genomes XV Conference

January 13-17, 2007
Town & Country Convention Center
San Diego, CA

Boron Tolerance Genes From Barley And Wheat

Margaret Pallotta , Tim Sutton , Thorsten Schnurbusch , Julie Hayes , Mahmood Hassan , Ute Baumann , Nick Collins , Peter Langridge

  Australian Center for Plant Functional Genomics, The University of Adelaide, PMB1 Glen Osmond, SA 5064, Australia

Boron toxicity in many low yielding environments is a significant limitation to crop productivity. In barley and wheat, genetic variation exists for tolerance to soil boron and the location of major loci is known from previous work. The major controlling loci in barley are on chromosomes 4H and 6H, and on 7B in wheat. In each case the favorable allele reduces the accumulation of boron in shoots and the deleterious morphological symptoms of growth under toxic conditions. A combination of positional cloning, yeast expression screening and transcript profiling has been used to identify the putative boron tolerance gene corresponding to the barley 4H locus.
The gene, named HvBO1, encodes a predicted membrane localised B transport protein. This result is consistent with earlier physiological data on the nature of boron exclusion from the roots of tolerance lines. Genetic mapping of HvBO1 demonstrated co-segregation with B tolerance in large F3 mapping populations. HvBO1 is not located in the syntenic intervals of either rice or Brachypodium. Southern analysis in barley indicated that the locus in the tolerant landrace Sahara may contain a tandem array of up to six duplicated copies of HvBO1.
The 7B wheat locus appears to represent a different gene. Fine mapping of the region surrounding the wheat gene is now well advanced.