Field Pea (Pisum sativum) Germplasm Screening for Seedling Ascochyta Blight Resistance and Genome-Wide Association Studies Reveal Loci Associated with Resistance to Peyronellaea pinodes and Ascochyta koolunga.

Ascochyta blight is a damaging disease that affects the stems, leaves, and pods of field pea (Pisum sativum) and impacts yield and grain quality. In Australia, field pea Ascochyta blight is primarily caused by the necrotrophic fungal species Peyronellaea pinodes and Ascochyta koolunga. In this study, we screened 1,276 Pisum spp. germplasm accessions in seedling disease assays with a mix of three isolates of P. pinodes and 641 accessions with three mixed isolates of A. koolunga (513 accessions were screened with both species). A selection of three P. sativum accessions with low disease scores for either pathogen, or in some cases both, were crossed with Australian field pea varieties PBA Gunyah and PBA Oura, and recombinant inbred line populations were made. Populations at the F3:4 and F4:5 generation were phenotyped for their disease response to P. pinodes and A. koolunga, and genotypes were determined using the diversity arrays technology genotyping method. Marker-trait associations were identified using a genome-wide association study approach. Trait-associated loci were mapped to the published P. sativum genome assembly, and candidate resistance gene analogues were identified in the corresponding genomic regions. One locus on chromosome 2 (LG1) was associated with resistance to P. pinodes, and the 8 Mb genomic region contains 156 genes, two of which are serine/threonine protein kinases, putatively contributing to the resistance trait. A second locus on chromosome 5 (LG3) was associated with resistance to A. koolunga, and the 35 Mb region contains 488 genes, of which five are potential candidate resistance genes, including protein kinases, a mitogen-activated protein kinase, and an ethylene-responsive protein kinase homolog.

Stimulation of HIV-specific T cell clonotypes using allogeneic HLA.

We hypothesized that HIV-specific CD8 T cell clonotypes can be stimulated by allogeneic HLA molecules. Multiple HIV-specific CD8 T cell clones were derived from 12 individuals with chronic HIV infection, specific for 13 different HIV Gag antigens and restricted to 7 different HLA molecules. The generated T cell clones were assayed for alloreactivity against a panel of single HLA class I expressing cell lines (SALs). HIV-specific T cells recognising at least one allogeneic HLA molecule could be identified from 7 of 12 patients tested. Allorecognition was associated with IFNγ cytokine production, CD137 upregulation and cytotoxicity, suggesting high avidity allo-stimulation. Allo-HLA recognition by HIV-specific T cells was specific to the HIV target peptide/HLA restriction and TCR TRBV usage of the T cells. HIV-specific T cells do crossreact against allogeneic HLA molecules in an epitope and TRBV specific manner. Therefore allo-HLA stimulation could be exploited to induce or augment HIV-specific T cell responses.