Genetic diversity, population structure and anthracnose resistance response in a novel sweet sorghum diversity panel

Authors: Cuevas, Hugo; Knoll, Joseph - Joe; Prom, Louis; STUTTS, LAUREN - University Of Florida; VERMERRIS, WILFRED - University Of Florida

Submitted to: Frontiers in Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/4/2023
Publication Date: 10/20/2023
Citation: Cuevas, H.E., Knoll, J.E., Prom, L.K., Stutts, L.R., Vermerris, W. 2023. Genetic diversity, population structure and anthracnose resistance response in a novel sweet sorghum diversity panel. Frontiers in Plant Science. 14: 1249555. https://doi.org/10.3389/fpls.2023.1249555.
DOI: https://doi.org/10.3389/fpls.2023.1249555

Interpretive Summary: The NPGS sweet sorghum germplasm collection is the primary source of genetic diversity for the development of new sweet sorghum varieties for biofuel production. To increase screening efficiency, a representative subset of 272 sweet sorghum accessions from the NPGS sweet sorghum collection was genetically characterized and data showed that its genetic diversity can be partitioned into four populations. This subset was evaluated across four locations for anthracnose resistance, one of the most limiting foliar diseases for biofuel production, and results identified 27 resistant accessions. Genome-wide association analysis identified 16 genomic regions associated with anthracnose resistance that enclose candidate resistance genes. This genetic characterization and identification of anthracnose resistant accessions identified valuable sweet sorghum germplasm that can be used by breeding programs working on sorghum as a source of biofuel.

Technical Abstract: Sweet sorghum is an attractive feedstock for the production of renewable chemicals and fuels due to the readily available fermentable sugars that can be extracted from the juice, and the additional stream of fermentable sugars that can be obtained from the cell wall polysaccharides in the bagasse. The sweet sorghum collection of the USDA-ARS National Plant Germplasm Systems (NPGS) consists of ~2,500 accessions and is the primary source of genetic diversity for the development of new sweet sorghum varieties for biofuel production. One of the selection criteria is resistance to anthracnose, a disease caused by the fungal pathogen Colletotrichum sublineolum that is prevalent in the warm and humid regions of the world where sweet sorghum is cultivated. Host resistance is the most effective and sustainable way to safeguard yields. The identification of novel anthracnose-resistance sources present in sweet sorghum germplasm offers a fast track towards the development of new resistant sweet sorghum germplasm by circumventing the protracted introgression process that is common when relying on resistance alleles from grain germplasm. We established a sweet sorghum diversity panel (SWDP) of 272 accessions that includes landraces from 22 countries and advanced breeding material, and that represents ~15% of the NPGS sweet sorghum collection. Genomic characterization of the SWDP identified 171,954 single nucleotide polymorphisms (SNPs) with an average of one SNP per 4,071 kb. Population structure analysis revealed that the SWDP could be stratified into four populations and one admixed group, and that this population structure could be aligned to sorghum’s racial classification. Results from a two-year replicated trial of the SWDP for anthracnose resistance response in Texas, Georgia, Florida, and Puerto Rico showed 27 accessions to be resistant across locations, while 145 accessions showed variable resistance response against local pathotypes. A genome-wide association study identified 16 genomic regions associated with anthracnose resistance. Comparative genome mapping analysis showed that three of these genomic regions have been previously associated to anthracnose resistance in grain sorghum. A genomic region of 41.6 kb at the tip of chromosome 8 was associated with resistance response observed in Georgia, Texas, and Puerto Rico. This publicly available SWDP and the extensive evaluation of anthracnose resistance represent a valuable genomic resource for the improvement of sorghum.