Diversity in @entity9725 @entity137 tolerance of Australian XXXX ( @entity2247 .) genotypes.

@entity137 @entity2247 @entity71235 @entity74 @entity9724 @entity9725
BACKGROUND: @entity9725 (B) is an important micronutrient for plant growth, but is toxic when levels are too high. This commonly occurs in environments with alkaline soils and relatively low rainfall, including many of the cereal growing regions of southern Australia. Four major @entity74 controlling tolerance to high soil B have been identified in the landrace @entity2247 , Sahara 3771. Genes underlying two of the loci encode the B transporters @entity9724 and @entity71235 . RESULTS: We investigated sequence and expression level diversity in @entity9724 and @entity71235 across @entity2247 germplasm, and identified five novel coding sequence alleles for @entity9724 . Lines were identified containing either single or multiple copies of the Sahara @entity9724 allele. We established that only the tandemly duplicated Sahara allele conferred B tolerance, and this duplicated allele was found only in a set of nine lines accessioned in Australian collections as Sahara 3763-3771. @entity71235 coding sequences were highly conserved across @entity2247 germplasm. We identified the likely causative SNP in the 5'UTR of Sahara @entity71235 , and propose that the creation of a small upstream open reading frame interferes with @entity71235 translation in Sahara 3771. Similar to @entity9724 , the tolerant @entity71235 allele was unique to the Sahara @entity2247 accessions. We identified a new source of the 2H B tolerance allele controlling leaf symptom development, in the landrace Ethiopia 756. CONCLUSIONS: Ethiopia 756, as well as the cultivar Sloop Vic which carries both the 2H and @entity9724 B tolerance alleles derived from Sahara 3771, may be valuable as alternative parents in breeding programs targeted to high soil B environments. There is significant diversity in B @entity137 tolerance among contemporary Australian @entity2247 varieties but this is not related to variation at any of the four known B tolerance loci, indicating that novel, as yet undiscovered, sources of tolerance exist.
