1a.Objectives (from AD-416)
A new late blight isolate, called blue 13 with fungicide resistance has recently taken a dominant position in Phytophthora populations in the United Kingdom, the Netherlands, Germany and France. These new isolates are more aggressive compared to the old population. While this new isolate is not yet present in the United States, we need to be prepared with germplasm that is resistant to highly virulent strains.
Our specific objectives are to:
1. Conduct transformations with candidate sequences of a putative S. microdontum R-gene.
2. Identify functional orthologs of the late blight R-gene RB from disease resistant wild germplasm and test the functionality of these genes using a transient expression assay.
3. Evaluate the late blight resistant potato advanced breeding lines including the varieties 'Defender' and 'Jacqueline Lee' for resistance to Blue 13 and identify the presence of genes that recognize P. infestans effectors.
4. Evaluate the effect of pyramiding the RB with conventionally bred late blight resistant lines.
1b.Approach (from AD-416)
Test the resistance phenotype of transgenic plants with the S. microdontum gene to P. infestans isolates collected from the United States and Guatemala.
Using primers conserved within the RB gene, we have successfully isolated RB-like sequences from ten different wild potato species. We are in the process of cloning these genes into an Agrobacterium tumefaciens binary expression vector under the control of a constitutive promoter. The sequence information shows that the genes are 85-95% similar to the RB gene from S. bulbocastanum and encode proteins of a similar length to the RB protein. The project is monitored through in person discussions, phone calls, and e-mail exchanges.