Researchers have identified new genetic resources that could help breeders develop sorghum varieties with stronger resistance to leaf rust, an important disease caused by the fungus Puccinia purpurea.

The peer-reviewed study, published in Scientific Reports, evaluated 278 accessions from the Sorghum Association Panel for susceptibility to rust. Field evaluations were conducted in Puerto Rico across multiple years.

Initial screening conducted in 2015 and 2022 identified 26 accessions without visible rust pustules. When those accessions were evaluated again in 2024, researchers confirmed 19 as consistently resistant, including 10 that repeatedly showed complete absence of rust pustules.

Scientists then analysed the plants genetically using 233,899 single-nucleotide polymorphisms (SNPs) and a genome-wide association approach.

The analysis identified six loci associated with rust resistance, located on sorghum chromosomes 1, 2, 5, 6, 8 and 9.

The strongest association occurred within a 33-kilobase region on chromosome 8, which the researchers designated Rp3.

That region contains four genes with BURP-domain homology:

Sobic.008G157500, Sobic.008G157600, Sobic.008G157700 and Sobic.008G157800.

The findings do not mean a new rust-resistant commercial sorghum variety has already been developed. Instead, the resistant accessions and associated genetic loci provide breeders and plant pathologists with candidate genetic resources for future resistance breeding and mechanistic studies.

For sorghum producers, disease resistance can be important because fungal infection can reduce plant health and productivity while increasing dependence on disease-management interventions.

The study could therefore contribute to longer-term breeding efforts aimed at developing sorghum germplasm with more durable resistance.