Retrospective genomic analysis of sorghum adaptation to temperate-zone grain production

Title 
Retrospective genomic analysis of sorghum adaptation to temperate-zone grain production 
Publication Type 
Journal Article 
Authors 
Thurber CS, Ma JM, Higgins RH, Brown PJ 
Year of Publication 
2013 
Volume 
14 
Journal 
Genome Biology 
Issue 
Pagination 
R68 
Date Published 
06/2013 
ISSN 
1465-6906 
Keywords 
Association Mapping, C4 photosynthesis, Dw1 locus, Dw2 V, Dw3 locus, dwarfism, Flowering time, GBS, Genome-wide mapping, Genotyping-By-Sequencing, Introgression, introgression mapping, photoperiod, QTL, Sorghum, Sorghum Conversion 
URL 
http://link.springer.com/article/10.1186/gb-2013-14-6-r68 
DOI 
10.1186/gb-2013-14-6-r68 
Abstract 
Background
Sorghum is a tropical C4 cereal that recently adapted to temperate latitudes and mechanized grain harvest through selection for dwarfism and photoperiod-insensitivity. Quantitative trait loci for these traits have been introgressed from a dwarf temperate donor into hundreds of diverse sorghum landraces to yield the Sorghum Conversion lines. Here, we report the first comprehensive genomic analysis of the molecular changes underlying this adaptation.
 
Results
We apply genotyping-by-sequencing to 1,160 Sorghum Conversion lines and their exotic progenitors, and map donor introgressions in each Sorghum Conversion line. Many Sorghum Conversion lines carry unexpected haplotypes not found in either presumed parent. Genome-wide mapping of introgression frequencies reveals three genomic regions necessary for temperate adaptation across all Sorghum Conversion lines, containing the Dw1, Dw2, and Dw3 loci on chromosomes 9, 6, and 7 respectively. Association mapping of plant height and flowering time in Sorghum Conversion lines detects significant associations in the Dw1 but not the Dw2 or Dw3 regions. Subpopulation-specific introgression mapping suggests that chromosome 6 contains at least four loci required for temperate adaptation in different sorghum genetic backgrounds. The Dw1 region fractionates into separate quantitative trait loci for plant height and flowering time.
 
Conclusions
Generating Sorghum Conversion lines has been accompanied by substantial unintended gene flow. Sorghum adaptation to temperate-zone grain production involves a small number of genomic regions, each containing multiple linked loci for plant height and flowering time. Further characterization of these loci will accelerate the adaptation of sorghum and related grasses to new production systems for food and fuel.

 

 
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