Location: Cereal Crops Research
Project Number: 3060-22000-050-05-R
Project Type: Reimbursable Cooperative Agreement
Start Date: Sep 1, 2018
End Date: Aug 31, 2021
1) Characterize the variability of the Spt1 extracellular receptor domain and how it is targeted by multiple P. teres necrotrophic effectors to facilitate disease. (2) Characterize the dominant resistance gene Rpt-CI5791 and the putative general P. teres elicitor/s that activates broad dominant resistance. ARS will work on the pathogen portions of both objective 1 and objective 2.
Identification of pathogen effectors using pathogen-mapping populations. Segregating pathogen populations, like barley mapping populations, can be used to characterize traits of interest. In previous work , we crossed two P. teres f. teres isolates (6A and 15A) that produce virulence factors that target the barley 6H region. Isolate 6A induces disease on the cultivar Rika and isolate 15A induces disease on the cultivar Kombar, both by interacting with different alleles of Spt1. To do this, we identified 468 SNP markers and used these markers to generate a genetic map for the characterization of pathogen virulence. Four major virulence loci were identified including two conferring virulence on Kombar (VK1 and VK2) and two conferring virulence on Rika (VR1 and VR2). These virulences, when genetically isolated, each correspond to the Spt1 locus on barley chromosome 6H. Using the current 15A × 6A genetic map in conjunction with additional next generation long read (PAC BIO) sequencing we assembled the genomic regions around these virulence genes and identified candidates for validation based on size (<50kDa), harboring a secretion signal, cysteine content, and lack of homology to other known fungal genes. A total of 16 strong candidates have been identified including five at VK1, three at VK2, five at VR1, and one at VR2. Validation and characterization of these candidates will be done using heterologous expression, gene transformation, and gene knockout experiments followed by evaluation of virulence of each transformed or mutant strain using the barley lines Rika and Kombar. Additionally, we will use a genome wide association study to identify the effectors involved in triggering C5791 resistance. A GWAS panel of 150 P. teres f. teres isolates have been phenotyped and 120 of these have been sequenced. A strong marker trait association has been identified and candidate genes adjacent to these markers will be evaluated.