Virus induced gene silencing to characterize candidate receptor-like proteins for brown stem rot resistance in soybean

Brown stem rot (BSR), caused by the soil borne fungal pathogen Phialophora gregata, is one of the top ten yield reducing pathogens for soybeans grown in the Northern United States. BSR symptoms are often confused with other soybean diseases or nutrient stress, making it difficult to characterize and deploy resistance in soybean breeding programs. Different genetic studies have suggest BSR resistance could be controlled by a single gene or as many as three tightly linked genes, all located on the same interval of chromosome 16. This interval contains 107 receptor-like proteins (RLPs), similar to disease resistance genes characterized from other species. The RLPs are arranged in distinct clusters, each with different sequence signature. To gain insight into BSR resistance mechanisms, we took advantage of virus induced gene silencing, which allowed us to turn off different RLP clusters or cluster combinations. If a cluster was required for resistance, turning it off would result in resistant plants that became susceptible to BSR. Using this approach we identified two clusters that are required for resistance to BSR in a line carrying the Rbs1 resistance gene. Using whole genome expression analyses, we developed a network of genes regulated by the two clusters of RLPs to confer resistance.