Identification of Novel R Gene Sequences from Thinopyrum intermedium

Stripe rust is a serious fungal disease of wheat present on all continents where wheat is cultivated. It is an important problem for Canada since year 2000 when some heat tolerant and more aggressive isolates were identified in western Canada. Every year new isolates of stripe rust are blown in Canada from USA and Mexico. At that time, there was very limited genetic resistance against satripe rust incorporated into Canadian wheat cultivars. If over 90 stripe rust resistance genes have been identified, only two genes are effective worldwide (Yr5 & Yr15). Five or six additional stripe rust resistance genes are also effective in most areas of North America. A unique challenge is the ability of stripe rust to make resistance gene inefficient in protecting wheat when exposed alone to the pathogen. Consequently different genes need to be pyramided together to offer stable and lasting resistance. Over sixty years ago, wild relatives of wheat such as intermediate wheatgrass were used to identify and move genes into wheat, a long and very difficult task. This lead to most of the genes that have been used so far to protect wheat against different pathogens. With the continual erosion of disease resistance genes by pathogens and given the small number of functional resistance genes available, there is an urgent need to identify novel and effective resistance genes to protect the Canadian wheat industry. Taking advantage of recently developped technologies, we have generated genes libraries from 15 individual lines of intermediate wheatgrass all highly resistant to stripe rust. Following the screening of these gene libraries that included sequencing and gene assembly, we identified 282 unique gene sequences representing putative novel resistance genes. We selected a subset of 66 putative genes present in all the lines to characterize their functionality. Based on the sequence of each putative gene, they were shown to belong to two classes of genes known to confer resistance against plant pathogens. We are at the step to re-synthesize them before demonstrating their functionality by inserting them into a wheat line susceptible to stripe rust to evaluate them against stripe rust.