Abstract
Forage sorghum (Sorghum bicolor (L.) Moench) is a wildly cultivated C4 cereal crop in many geographical regions and differs among germplasms in a number of important physiological traits. Lignin is a complex heteropolymer found in plant cell walls that adversely affects economic and environmental benefits of the crop. To understand the genetic basis, we re-sequenced the genomes of 206 sorghum accessions collected around the globe and identified 14,570,430 SNPs and 1,967,033 indels. Based on the SNP markers, we characterized the population structure and identified loci underlying lignin content by genome-wide association studies (GWAS). Analysis of the genetic relationships among the accessions revealed a more diverse spread of sorghum accessions and breeding lines from Asia, America, and their genetically improved variety, but a limited genetic diversity in the European accessions. These findings add new perspectives to the historical processes of crop diffusion within and across agroclimatic zones of America, Asia, and Europe. GWAS revealed 9 quantitative trait loci (QTLs) for lignin content, harboring 184 genes. These genes were significantly enriched into 7 major gene ontology (GO) terms involved in plant-type cell wall organization or bioenergy. The alleles of 9 QTLs in the 206 accessions were geographically distributed. The findings provide us with an understanding of the origin and spread of haplotypes linked to lignin content. The findings will allow improvements to feed quality and adaptation to stresses in sorghum, through the rapid increase of genetic gains for lignin content.
Highlights
Sorghum (Sorghum bicolor (L.) Moench) is the fifth leading cereal crop worldwide in both subsistence and commercial agriculture systems, in semiarid regions such as sub-Saharan Africa and South Asia (National Research Council 1996; Mundia et al 2019)
The findings provide us with an understanding of the origin and spread of haplotypes linked to lignin content
Sorghum bicolor is highly adaptable across an extensive geographic range; sources for the improvement of traits may be found in traditional varieties from Africa and Asia (National Research Council 1996; Casa et al 2008; Upadhyaya et al 2009; Vermerris 2011; Morris et al 2013; Mathur et al 2017; Mundia et al 2019)
Summary
Sorghum (Sorghum bicolor (L.) Moench) is the fifth leading cereal crop worldwide in both subsistence and commercial agriculture systems, in semiarid regions such as sub-Saharan Africa and South Asia (National Research Council 1996; Mundia et al 2019). 73 Page 2 of 13 grain sorghum, course forage sorghum, often used for green chop, hay, silage, and pasture (Shoemaker and Bransby 2010), grows quickly, is morphologically taller and leafier, and matures later with a higher biomass and a juicy stem, but relatively lower seed yield (Harlan and De Wet 1972; Getachew et al 2016). It has been identified as a potential target for sugar as well as the production of lignocellulosic biofuels (Mathur et al 2017). The complex genetics for these remarkable traits of forage sorghum have not been well elucidated
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