Location: Foreign Disease-weed Science Research2013 Annual Report
1a. Objectives (from AD-416):
The objective of the proposed research is to identify putative resistance genes using a combination of bioinformatics, gene expression analysis, and virus-induced gene silencing (VIGS) assays to investigate the role of specific genes and pathways that provide resistance against select isolates of soybean rust.
1b. Approach (from AD-416):
Putative resistance genes will be identified through gene mapping, soybean gene expression studies, and from a comparative bioinformatic analysis of the soybean genome. Using virus-induced gene silencing these candidate genes will be silenced, or "turned off", in soybean plants that display resistance towards select isolates of soybean rust. Silenced plants will then be evaluated for a breakdown of resistance by challenging the plants with the pathogen and scoring for the development of disease. A combination of RT-PCR (to assess gene silencing) and gene sequencing will be used to complete the VIGS analysis.
3. Progress Report:
Rpp3 is one of six soybean genes that were identified through germplasm screening efforts aimed at identifying sources of resistance to the fungal pathogen that causes the disease known as Asian soybean rust. We have been using a virus-induced gene silencing (VIGS) system to target candidate Rpp3 genes to ascertain the true identity of Rpp3. A preliminary loss-of-function phenotype using VIGS has been obtained for one of the candidate genes. To aid in our analysis, we constructed two bacterial artificial (BAC) libraries in an effort to identify genes or alleles unique to soybean lines containing Rpp3. Unfortunately, this approach using BACs was unsuccessful since the region containing Rpp3 appears to be unstable in E. coli. This observation is consistent with our inability to clone PCR amplicons containing the Rpp3 region.