Project Number: 8080-21000-026-03-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Sep 18, 2017
End Date: Sep 17, 2018
The objectives for this project will be to: 1) determine the phenotypic response of specific assessions of USDA-ARS, National Plant Germplasm System (NPGS) apple collection to fire blight in order to identify germplasm donor stocks with potentially novel allelic variants at known fire blight resistant loci and to identify accessions with potentially novel resistance loci for fire blight; 2) conduct multiplex polymerase chain reaction (PCR) for five known major fire blight resistance loci on fire blight resistance accessions to classify genetic loci determining resistance or identify potentially novel sources of resistance; and 3) dissemination of phenotypic data for fire blight resistance and marker loci classification through the Germplasm Resources Information Network (GRIN)-Global database.
The project will perform a primary screen of accessions already identified as very resistant (1-2 score) in the GRIN-Global database with a mixture of strains (~3-5 strains) of Erwinia amylovora. From the preliminary screen, 304 resistant (1-2 score) Malus accessions will be selected to perform an in-depth secondary inoculation study with three individual strains with differential virulence and pathogenicity. The inoculation with individual strains is expected to identify varying patterns from highly resistant to highly susceptible on individual accessions, revealing strain-specific genes/alleles/combinations as well as broad-spectrum resistance. This will not only identify donors for novel strain-specific major genes, considered less durable, but it can also identify potential donors for partial and more durable resistance. The project will also develop a multiplex PCR with markers to amplify genes or markers flanking major fire blight QTLs, and amplify these five fire blight loci in all resistant (1-2 score) accessions from the primary screening to identify alleles coupled with fire blight resistance. This data will also be used to identify the number of resistant genotypes per Malus species, estimate frequencies of alleles, pedigree and sources of these five major loci, their allelic variants, and speculate origin of resistance. Information on resistance alleles and phenotype data will be made available to the wider apple research community and industry through GRIN-Globaldatabase.