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19SUMMER 2015 SPUDSMART.COM LENGTHY SEARCH This genetic breakthrough has been a long time coming. The international team of scientists began their gene research by focusing on proteins considered essential to P. infestans. According to Wageningen University researcher Vivianne Vleeshouwers the discovery has its roots in an old theory the so-called Achilles heel hypothesis. A problem of breeding for late blight resistance is that introduced resistance genes get quickly overcome by the late blight pathogen. This means that the pathogen can adapt by changing the protein that is recognized by the resistance gene in the potato. The Achilles heel theory says that if we target a protein that is essential to the pathogen then it is less likely that it will adapt she says. The approach we took is only recently possible thanks to availability of genome sequencing of phytophthora and an experimental approach effectoromics that we designed to be able to screen individual genes in a high- throughput fashion. Scientists found this essential protein in elicitin in the late 1980s initially due to work done by a research group working at the French National Institute for Agricultural Research. Many years of screening wild potatoes for elicitin resulted in its discovery in Solanum microdontum a South American wild relative of cultivated potatoes. ELR encodes a receptor-like protein in S. microdontum. Plants contain many of these cell surface receptors which act as a first line of immune defence much like an array of radar antennas. The receptors are tuned to different features of invading pathogens and in the case of this new type of blight-resistant potato the simultaneous presence of elicitin and the gene that responds to it triggers cell death at the site of infection. Its this powerful plant defense mechanism that restricts the progress of the late blight pathogen. There are two classes of immunity receptors in plants. One class functions inside the plant cell and the other on the surface of the plant cell. In VIVIANNE VLEESHOUWERS I think this new layer of immunity has big potential for control of late blight on a world scale. The sporangia of Phytophthora infestans the pathogen responsible for late blight disease. PHOTO LAWRENCE KAWCHUK AAFC The knowledge were getting at the micro-level through genomics research is having a big impact on how we can combat late blight. BENOIT BIZIMUNGU the past for potato blight weve only known about the receptors that work inside the plant cell. This is the first report of a cell surface type of immune receptor against the blight Kamoun says. For resistance to be deemed durable it needs to hold over time but looking at this research the new gene is really broad-based. It is expected to offer more durable resistance in theory Bizimungu says. The knowledge were getting at the micro-level through genomics research is having a big impact on how we can combat late blight. Canadian research played a role in the discovery. Researchers in England and the Netherlands drew upon the work of Lawrence Kawchuk an Agriculture and Agri-Food Canada research scientist based in Alberta. In 2001 he isolated one of the first plant disease receptors for verticillium wilt resistance which helps to prevent early dying in potato plants. NEW LAYER OF IMMUNITY For potato growers the late blight breakthrough is significant because it may help circumvent the pathogens major strength its ability to evolve and create new versions of itself that overcome resistance that have been bred into potatoes. I think this new layer of immunity has big potential for control of late blight on a world scale. The research is still in the experimental phase and is not strong enough yet to apply in practice. We need more research to find out how