Comparative evolutionary genetics of deleterious load in sorghum and maize

Sorghum and maize share a close evolutionary history that can be explored through comparative genomics(1,2). To perform a large-scale comparison of the genomic variation between these two species, we analysed ~13 million variants identified from whole-genome resequencing of 499 sorghum lines together with 25 million variants previously identified in 1,218 maize lines. Deleterious mutations in both species were prevalent in pericentromeric regions, enriched in non-syntenic genes and present at low allele frequencies. A comparison of deleterious burden between sorghum and maize revealed that sorghum, in contrast to maize, departed from the domestication-cost hypothesis that predicts a higher deleterious burden among domesticates compared with wild lines. Additionally, sorghum and maize population genetic summary statistics were used to predict a gene deleterious index with an accuracy greater than 0.5. This research represents a key step towards understanding the evolutionary dynamics of deleterious variants in sorghum and provides a comparative genomics framework to start prioritizing these variants for removal through genome editing and breeding. Comparative genomics revealed similar distribution patterns of deleterious mutations in maize and sorghum but a post-domestication reduction of genetic load in sorghum, which is probably caused by sorghum's high selfing rate and unique domestication history.

Automated summary

Comparative analysis of genomic variations between sorghum and maize revealed prevalent deleterious mutations in both species, particularly in pericentromeric regions, with sorghum showing a lower post-domestication genetic load compared to maize. This research provides insights into the evolutionary dynamics of deleterious variants in sorghum and offers a framework for prioritizing these variants for removal through genome editing and breeding.