Abstract
Key messageCoordinated association and linkage mapping identified 25 grain quality QTLs in multiple environments, and fine mapping of theWxlocus supports the use of high-density genetic markers in linkage mapping.There is a wide range of end-use products made from cereal grains, and these products often demand different grain characteristics. Fortunately, cereal crop species including sorghum [Sorghum bicolor (L.) Moench] contain high phenotypic variation for traits influencing grain quality. Identifying genetic variants underlying this phenotypic variation allows plant breeders to develop genotypes with grain attributes optimized for their intended usage. Multiple sorghum mapping populations were rigorously phenotyped across two environments (SC Coastal Plain and Central TX) in 2 years for five major grain quality traits: amylose, starch, crude protein, crude fat, and gross energy. Coordinated association and linkage mapping revealed several robust QTLs that make prime targets to improve grain quality for food, feed, and fuel products. Although the amylose QTL interval spanned many megabases, the marker with greatest significance was located just 12 kb from waxy (Wx), the primary gene regulating amylose production in cereal grains. This suggests higher resolution mapping in recombinant inbred line (RIL) populations can be obtained when genotyped at a high marker density. The major QTL for crude fat content, identified in both a RIL population and grain sorghum diversity panel, encompassed the DGAT1 locus, a critical gene involved in maize lipid biosynthesis. Another QTL on chromosome 1 was consistently mapped in both RIL populations for multiple grain quality traits including starch, crude protein, and gross energy. Collectively, these genetic regions offer excellent opportunities to manipulate grain composition and set up future studies for gene validation.
Highlights
Sorghum [Sorghum bicolor (L.) Moench] is a subsistence crop across the semi-arid tropics in sub-Saharan Africa and Southern Asia, where the grain is a dietary staple for an estimated half billion people (National Research Council 1996)
Starch in the grain sorghum diversity panel (GSDP) had the greatest range of phenotypic variation (>30%) followed by crude protein, crude fat, and gross energy (Table 1)
Gross energy in the GSDP contained the smallest amount of phenotypic variation, a 400 kcal kg−1 (10.2%) difference was observed between the lowest and highest accession
Summary
Sorghum [Sorghum bicolor (L.) Moench] is a subsistence crop across the semi-arid tropics in sub-Saharan Africa and Southern Asia, where the grain is a dietary staple for an estimated half billion people (National Research Council 1996). Like other cereal crops, can be utilized to create additional end-use products. Sorghum grain has been used to make baking flours, pop sorghum, alcoholic beverages, Theor Appl Genet (2017) 130:697–716 pet foods, and packaging materials (Fang and Hanna 2000; Udachan et al 2012; Zhu 2014). These various products can require different grain characteristics and can alter crop ideotype. Understanding the chemical and genetic components underlying the gross energy content of sorghum would enable breeders to increase the overall feed efficiency when the grain is grown for livestock feed through selective breeding and trait introgression
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