P-014 - Autoimmune responses with plant growth arrest are induced in hybrids between common wheat and synthetic hexaploids derived from wild einkorn wheat.

Misconnection of plant immunity genes in hybrids causes hybrid incompatibility. Polyploid wheat has a significantly higher number of nucleotide-binding leucine-rich repeat receptors and receptor-like kinases than diploid species. However, how polyploid wheat stabilizes its immune gene network and prevents misconnections remains unclear. We developed 38 synthetic hexaploid wheat lines by crossing durum wheat cultivar ‘Langdon’ with wild einkorn followed by genome doubling with colchicine. When these synthetic lines were crossed with common wheat, the F₁ hybrids exhibited hybrid incompatibility with plant growth arrest. To identify the causal genomic region, we crossed the synthetic lines with wheat nulli-tetrasomic and 5D chromosome deletion lines and evaluated phenotypes of the F₁ hybrids. Genome sequencing of the deletion lines narrowed the candidate region to a 25.4 Mbp on the short arm of chromosome 5D. To identify a causal gene, we developed high efficiency of simultaneous genome editing using CRISPR/Cas9 applying tRNA processing system. By simultaneously expressing six sgRNAs per gene, we achieved up to 100% editing efficiency at all homoeologous loci in hexaploid wheat. Genome-edited plants for several candidate genes were obtained and crossed with the synthetic hexaploid line. Identification of the causal gene will help elucidate how polyploid wheat stabilizes its plant immunity gene network.