Submitted to: The Plant Genome
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/14/2017
Publication Date: N/A
Citation: N/A Interpretive Summary: Durum wheat in comparison to common wheat represents only a small portion (5-6%) of annual global wheat production and is considered to be a minor cereal crop worldwide. The vast production differential between these two wheat relatives is due in part because the very hard, vitreous durum kernels are difficult to process mechanically, resulting in a coarse ground semolina as opposed to the regularly milled finer-textured hard and soft common wheat flours, which unfortunately has far fewer commercial end-use food product applications and capabilities. The objectives of this research were to: (1) characterize the size and breakpoint of the 5DS(5BS) Chinese Spring translocation carrying the Ha locus in Soft Svevo and other soft durum germplasm and (2) determine if there were any other genomic implications surrounding this translocation event. The 5DS(5BS) ‘Chinese Spring’ translocation carrying the Ha locus has transformed the kernel texture in durum wheat from extremely hard to soft with pleiotropic effects on end-use quality. Near-isogenic lines are genotypes that are nearly identical except at one genomic location, and changes detected in NILs are candidate genomic regions that may contain introgressions. Here, NIL genotyping and BLASTn results were used to estimate the size of the 5DS(5BS) Chinese Spring translocation, which was estimated at ~24 Mbp.
Technical Abstract: Cultivar ‘Soft Svevo’, a new non-GMO soft durum cultivar with soft kernel texture, was developed through a 5DS(5BS) chromosomal translocation from event. cv. Chinese Spring, and subsequently used to create new soft durum germplasm. The development of Soft Svevo featured the Ph1b-mediated homoeologous transfer of the Puroindoline genes at the Ha locus on chromosome 5DS, but the size of the translocation, its estimated breakpoint, and other genomic implications surrounding the translocation event remain unknown. In 2014, four near-isogenic pairs of hard and soft durum genotypes, in addition to Soft Svevo and the 5DS-2 Chinese Spring deletion line, were genotyped using Illumina’s 90 000 wheat SNP array. SNP results were processed in Genome Studio and in total 164 polymorphic markers were identified between the NILs. Of them, subsequent BLASTn results for two subsets of markers, corresponding to the distal end of the short arms of chromosome 5D and 5B, respectively, suggest that a ~20 Mbp or ~22.92 cM region of chromosome 5BS was lost from the 5DS(5BS) translocation event, and that the size of the 5DS chromosome present in the soft durum germplasm is ~24 Mbp in length or ~105.37 cM. GISH images of the soft durum NILs generally agree with these estimates. Soft durum represents the potential of a new wheat market class and these findings will assist durum wheat breeders in the development of new soft durum germplasm.