Genome-wide association study reveals that different pathways contribute to grain quality variation in sorghum (Sorghum bicolor)

Abstract

Background: In sorghum (Sorghum bicolor), one paramount breeding objective is to increase grain quality. The nutritional quality and end use value of sorghum grains are primarily influenced by the proportions of tannins, starch and proteins, but the genetic basis of these grain quality traits remains largely unknown. This study aimed to dissect the natural variation of sorghum grain quality traits and identify the underpinning genetic loci by genomewide association study. Results: Levels of starch, tannins and 17 amino acids were quantified in 196 diverse sorghum inbred lines, and 44 traits based on known metabolic pathways and biochemical interactions amongst the 17 amino acids calculated. A Genome-wide association study (GWAS) with 3,512,517 SNPs from re-sequencing data identified 14, 15 and 711 significant SNPs which represented 14, 14, 492 genetic loci associated with levels of tannins, starch and amino acids in sorghum grains, respectively. Amongst these significant SNPs, two SNPs were associated with tannin content on chromosome 4 and colocalized with three previously identified loci for Tannin1, and orthologs of Zm1 and TT16 genes. One SNP associated with starch content colocalized with sucrose phosphate synthase gene. Furthermore, homologues of opaque1 and opaque2 genes associated with amino acid content were identified. Using the KEGG pathway database, six and three candidate genes of tannins and starch were mapped into 12 and 3 metabolism pathways, respectively. Thirty-four candidate genes were mapped into 16 biosynthetic and catabolic pathways of amino acids. We finally reconstructed the biosynthetic pathways for aspartate and branched-chain amino acids based on 15 candidate genes identified in this study. Conclusion: Promising candidate genes associated with grain quality traits have been identified in the present study. Some of them colocalized with previously identified genetic regions, but novel candidate genes involved in various metabolic pathways which influence grain quality traits have been dissected. Our study acts as an entry point for further validation studies to elucidate the complex mechanisms controlling grain quality traits such as tannins, starch and amino acids in sorghum.

Genome wide association mapping of epi-cuticular wax genes in Sorghum bicolor

“…The LGS1 (Sobic.005G213600) dependent Striga resistance in sorghum is based on the abiotic conditions and often greatly reduce the expression of photosystem genes (Bellis et al 2020). The other important genes from our studies include Sobic.005G225500 (DUF1618) involved in the starch biosynthesis in sorghum (Campbell et al 2016), Sobic.004G156000 (steroleosin) functions as lysine degrader in sorghum (Kimani et al 2020), and Sobic.009G140500 (NAM protein) involved in transcriptional regulation (Fang et al 2008). The role of identified candidate genes for EW biosynthesis and transport in sorghum is discussed in the following section.…”

Sorghum pan-genome explores the functional utility to accelerate the genetic gain

“…The GWAS performed in the earlier study was limited to the phenotype association only with limited SNPs on the reference genome used (Kimani et al ., 2020; Morris et al ., 2013). The SNP calling on sorghum pan-genome has enabled to identify the variants also from non-reference sequence assembly from the genetically diverse accessions.…”

A Review on the Cooking Attributes of African Yam Bean (Sphenostylis stenocarpa)

“…Over the years, GWAS has been implemented across a wide variety of crops such as soybean, maize, common bean, sorghum, and rice [55,[138][139][140][141]. GWAS identifies genetic variants across the genome and associates the variants with the target phenotype.…”