2011 Annual Report
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)
Stable transformation of LB susceptible potato with candidate resistance genes. Transgenic plants will be evaluated for resistance to LB. Crossing transgenic plants containing the RB gene or the newly discovered gene with conventionally bred LB resistant varieties will also be done.
A candidate R-gene for late blight resistance was cloned from S. microdontum. The sequence of the gene was similar to blb3. The R-gene was cloned into a pBI121-derived vector driven by a constitutive promoter and we have conducted Agrobacterium-based transformations. These transformation experiments resulted in over 40 lines that are polymerase chain reaction (PCR) positive for the candidate R-gene. These lines are being propagated so that bioassays and further molecular characterization can be conducted. The project is monitored through in person discussions, phone calls, and e-mail exchanges.