Genome-Wide Association Study for Plant Architecture and Bioenergy Traits in Diverse Sorghum and Sudangrass Germplasm

Sorghum is an important grain, forage, and bioenergy crop. The objective of this study was to identify genetic signals associated with plant architecture and bioenergy traits in sorghum and sudangrass germplasm through a genome-wide association study (GWAS). Plant height (HT), tiller number (TN), internode number (IN), stem diameter (SD), panicle length (PL), panicle weight (PW), reducing sugar (RS) content, Brix, and protein (PRO) content were assessed in 300 germplasm consisting of grain sorghum, sweet sorghum, sudangrass, sweet sorghum-sweet sorghum recombinant inbred lines (RILs) and sudangrass-sudangrass RILs grown in three different environments over two years. Large variations of phenotypic traits were observed in the population panel. The heritability of traits were all higher than 0.5, ranging from 0.52 (PRO) to 0.92 (HT) with an average of 0.76. The population exhibited three population structures (Q) and minor relative kinship (K), assessed by using 7982 single-nucleotide polymorphisms (SNPs). After controlling Q and K, GWAS identified 24 SNPs that were significantly associated with traits, including three SNPs with HT, four with TN, four with PL, three with Brix, and ten with RS. Of them, seven SNPs were novel signals that were not identified previously, including one for HT, one for TN, one for Brix, and four for RS. The putative candidate genes involved in brassinosteroid regulatory pathway, auxin biosynthesis, carbohydrate metabolism, and sugar transport were identified underlying the significant SNPs. Identification of SNP signals and related candidate genes would enrich the current genomic resource for further molecular breeding aimed at improvement of food, feed, and biofuel productions of sorghum.