Location: Crop Genetics and Breeding Research
Project Number: 6048-21000-030-006-I
Project Type: Interagency Reimbursable Agreement
Start Date: Sep 15, 2018
End Date: Sep 14, 2022
Objective:
1) uncovering additional anthracnose resistance sources present in the Sorghum Association Panel (SAP),
2) mining the NPGS collection for multiple resistance alleles,
3) validating four newly identified resistance genes in susceptible sweet sorghum germplasm, and
4) understanding the molecular function of these four newly identified resistance genes.
Approach:
Three sets of RILs (>200 lines per population) from sorghum NAM population segregating for anthracnose resistant response will be evaluated against multiple C. sublineolum pathotypes from Puerto Rico, Texas, Georgia, and Florida through a two-year replicated field trial employing the screening methodology from Prom et al. (2009). High-density recombination linkage maps previously constructed based on genotyping by sequencing (GBS) of the lines will be used to delimit genomic regions associated with resistant response based on linkage analysis. It is evident that this family-based approach will not uncover all resistance sources present in the SAP. Therefore, to increase frequency of resistance alleles in the SAP, NPGS exotic accessions belonging two four major sorghum races will be genotyped and characterized for anthracnose resistant response. We propose to select a total of 400 NPGS exotic accessions belonging to Guinea and Kafir sorghum races, to complement the previous efforts for NPGS Ethiopian (Durra), SAP, sweet sorghum, and Sudan (Caudatum). Principal component analysis (PCA) and neighbor-joining trees will be used to investigate the population structure of this diverse panel of >1300 accessions. Genome-wide association study (GWAS) using a mixed linear model (MLM) approach and logistic regression (i.e. resistant or susceptible) will be completed to identify novel anthracnose resistance loci. Comparative analysis among anthracnose resistant loci identified based on GWAS and family approach will complement our understanding of host/pathogen relationships present in different sorghum races.
Our current project has identified four resistance genes (three on chromosome 5, one on chromosome 9) for which we propose to validate and investigate the molecular mechanism leading to anthracnose resistance. Given the regulatory function of these genes, we will perform expression profiling of infected and mock-inoculated tissue over time and identify coordinately expressed genes. In addition, by resequencing these four genes from a representative subset of 384 accessions selected based on the previous phylogenetic analysis, we can associate the presence of particular alleles with anthracnose resistance, and determine how this correlates with expression profiles. In parallel, the four genes will be validated based on introgression to a highly susceptible sweet sorghum germplasm. Seven resistant lines (SC15, SC110, SC1330, SC17, SC1321, SC155, SC13) that contain multiple resistance alleles for the different loci will be crossed with the highly susceptible sweet sorghum line ‘Early Honey' (PI 641897). Genetic markers (e.g. KASP) based on single nucleotide polymorphism (SNPs) will be developed and used to select for resistance alleles in the BC1F1 generation and to later fix them in the BC1F2 generation. Selected plants will be advanced until BC1F4 and evaluated for anthracnose resistant response and sugar content (i.e. °Brix) in a replicated trial in Georgia, Florida and Puerto Rico.
