INVESTIGATORS: Hugo Cuevas (PI), Louis Prom, Joseph Knoll, Wilfred Vermerris
INSTITUTIONS: USDA ARS Tropical Agriculture Research Station, Mayaguez PR; USDA ARS Crop Germplasm Research Unit, College Station TX; USDA ARS Crop Genetics and Breeding Research Unit, Tifton GA; University of Florida Gainesville
PROJECT SUMMARY: Sorghum [Sorghum bicolor (L.) Moench] is the fifth most important grain crop behind maize, wheat, rice, and barley, and an important source of fermentable sugars from grain, soluble stem sugars and biomass. Nevertheless, the productivity and profitability of sorghum is limited by several biotic constraints, most notably anthracnose caused by the aggressive fungal pathogen Colletotrichum sublineolum. The most effective and environmentally responsible strategy to control anthracnose is through the incorporation of resistance genes, but although several sources have been identified, the lack of information with regard to its genetic control has limited their adequate use in breeding programs. Therefore, the objectives of this proposal are to use a genomics-based approach to identify anthracnose resistance loci from diverse sorghum germplasm, to establish against which pathotypes the resistance alleles at these loci protect, and to determine the disease resistance mechanism of at least one of these genes, with the ultimate goal of providing plant breeders with a tool kit that can be used to provide maximum levels of resistance in the intended area of production.
Three sets of recombinant inbred lines (RILs) derived from the cross of three different sources of resistance originally from Ethiopia, India, and Sudan (SC112-14, QL3 and IS18760, respectively) to a common highly susceptible line PI609251 will be evaluated against pathotypes from Florida, Georgia, Texas and Puerto Rico. High-resolution linkage maps of RILs based on genotyping-by sequencing (GBS) will be used to delineate genomic regions and to identify candidate genes. Simultaneously, a reduced sample of RILs selected based on complementary recombinational breaking points will also be evaluated in the greenhouse against subsets of particular pathotypes from these locations to dissect anthracnose resistance loci into their multiple gene components. In parallel, through a combination of fine-mapping, expression analysis, and virus-induced gene silencing with Brome mosaic virus, the anthracnose resistance response against Florida pathotypes present in cultivar Bk7 will be investigated to provide information on the molecular mechanism controlling anthracnose resistance.
This family-based approach will be complemented with the evaluation of a diversity panel of ~200 genetically and geographically diverse accessions with high sugar content (>15.0 Brix). The GBS analysis of this panel will be employed for genome-wide association analysis to identify novel anthracnose resistance loci that are already in a sweet sorghum background. The complementary results of these experiments will allow dissection of the anthracnose resistance response into its multiple gene components with the ultimate goal of understanding the host/pathogen relationship present in different sorghum types to accelerate breeding for anthracnose resistance in sweet sorghum.
Name: Cuevas, Hugo