Phylogenetic relationships in the Sorghum genus based on sequencing of the chloroplast and nuclear genes

Abstract

Sorghum [Sorghum bicolor (L.) Moench] is an important food crop with a diverse gene pool residing in its wild relatives. A total of 15 sorghum accessions from the unexploited wild gene pool of the Sorghum genus, representing the five subgenera, were sequenced, and the complete chloroplast genomes and 99 common single-copy concatenated nuclear genes were assembled. Annotation of the chloroplast genomes identified a total of 81 protein-coding genes, 38 tRNA, and four rRNA genes. The gene content and gene order among the species was identical. A total of 153 nonsynonymous amino acid changes in 40 genes were identified across the species. Phylogenetic analysis of both the whole chloroplast genome and nuclear genes revealed a similar topology with two distinct clades within the genus. The species within the subgenera Eusorghum, Chaetosorghum, and Heterosorghum clustered in one clade, whereas the species within the subgenera Parasorghum and Stiposorghum clustered in a second clade. However, the subgenera Parasorghum and Stiposorghum were not monophyletic, suggesting the need for further research to resolve the relationships within this group. The close relationship between the two monotypic subgenera Chaetosorghum and Heterosorghum suggests that species within these subgenera could be considered as one group. This analysis provides an improved understanding of the genetic relationships within the Sorghum genus and defines diversity in wild sorghum species that may be useful for crop improvement. INTRODUCTIONSorghum [Sorghum bicolor (L.) Moench] is a versatile food crop globally and a staple food in many African and Asian

Cyanogenesis in the Sorghum Genus: From Genotype to Phenotype

“…Access to preliminary genome sequence data for six CWR ( S. laxiflorum , S. macrospermum , S. brachypodum , S. leiocladum , S. matarankense and S. purpureosericeum [ 35 ]) enabled the analysis of the variation present in selected genes involved in cyanogenesis and related pathways. Briefly, the trimmed reads were mapped to the genomic sequences of the 18 selected S. bicolor genes ( Supplementary Table S2 ).…”

“…The available sequences of a series of selected genes in the genomes of 6 wild sorghum species [ 35 ] were used to analyze the variation in 18 genes selected based on known and putative roles in cyanogenesis (dhurrin biosynthesis, bioactivation, recycling) as well as in the synthesis of tyrosine (the amino acid substrate for the first step in dhurrin biosynthesis) and ethylene ( Supplementary Table S2 ). The S. bicolor genomic sequences for these genes were downloaded to CLC from Phytozome ( , accessed on 10 January 2022) and used to map the reads generated from the partial sequencing of the six wild Sorghum species.…”

“…Currently, there are 25 recognized species within the Sorghum genus, separated into 5 morphologically distinct sub-genera: Eusorghum, Chaetosorghum, Heterosorghum, Parasorghum and Stiposorghum ( Figure 1 ) [ 33 , 34 , 35 ]. Sorghum bicolor , all S. bicolor subspecies and landraces, domesticated Sorghum varieties and interspecific naturalized domesticated × wild hybrids belong to the Eusorghum .…”

Transcript profiles of wild and domesticated sorghum under water-stressed conditions and the differential impact on dhurrin metabolism

“…On the other hand, wild sorghum species such as S. macrospermum with a very low dhurrin content in their leaves can be “redomesticated” by introducing genes related to higher yield and biomass from the already domesticated sorghum species e.g., as shown in wild tomato (Lemmon et al 2018 ; Zsögön et al 2018 ). The close phylogenetic relationship of domesticated S. bicolor and the wild species S. macrospermum (Ananda et al 2021 ) provides a great advantage to the introgression of beneficial traits of sorghum species.…”

“…A major constraint in utilising the genetic resources in wild crop relatives is hindrance in gene transfer between domesticated crops and their wild relatives (Bevan et al 2017 ). However, the Australian endemic wild sorghum species, S. macrospermum is closely related to domesticated S. bicolor (Ananda et al 2021 ), with successful introgression of the two species reported by Kuhlman et al ( 2010 ). The regulation of the synthesis of dhurrin in wild sorghum species in comparison to domesticated S. bicolor has not been studied.…”