Genome-Wide Association Study of Nigerien and Senegalese Sorghum Genotypes for their Response to Downy Mildew

Sorghum, a multipurpose and drought-tolerant crop, will play an integral role in future food security, especially in the drier tropics. In Niger and Senegal, sorghum supplies the daily caloric needs of millions of inhabitants. One of the major constraints to sorghum production is downy mildew incited by Peronosclerospora sorghi. In this communication, we report the results of a genome-wide association study (GWAS) of a subset of the 120 accessions from Niger and Senegal for downy mildew response under natural infection. The GWAS revealed several loci that have already been reported for their role in plant disease resistance response. Significant SNPs identified on chromosomes 1 and 5 traced back to genomic regions neighboring loci coding for transcription factors involved in biotic stress response. On chromosome 4, the SNP identified was less than 5 kb apart from a gene coding for an E3 ubiquitin ligase enzyme that regulates gene expression levels in relation to plant disease resistance. A membrane-bound protein involved in programmed cell death on chromosome 6 and a transposase on chromosome 8 were identified. Furthermore, a SNP locus that has not been reported previously for biotic stress response was also identified on chromosome 10. This SNP was 4.94 kb downstream of Sobic.010G172100, which encodes a protein similar to the basic helix-loop-helix (bHLH) transcription factor. bHLHs are known for their role in abiotic stress responses. Further work to validate and confirm the activities of the identified SNPs in resistance response will be conducted.