2012 Annual Report
1a.Objectives (from AD-416):
In 2009, a new late blight strain US-22 was identified along the East coast and as far west as Wisconsin. This strain was virulent on potatoes and significantly impacted potato production in affected areas. There was greater variation in the strains identified in potato fields in the U.S. in 2010, however US-22 was again identified in WI along with US-23 and 24. Although not yet present in the USA, destructive and highly virulent strains of P. Infestans have spread through Europe (genotype Blue 13), and are present in Guatemala (currently uncharacterized). These new strains can be much more aggressive compared to the old populations. We need to be prepared with germplasm that is resistant to highly virulent strains.
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.
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.
Our recent work has located this late blight resistance to Chromosome 4 in potato. Based upon further analysis, we hypothesize that this late blight resistance location may be associated with the R2 gene complex, a location where several other genes for late blight resistance have been found. We have identified and sequenced a blb-3-like R-gene from this material and engineered the gene into a vector so that it is driven by a constitutive promoter for expression within plants. We have introduced the gene through Agrobacterium-based transformation into a susceptible potato line and are currently in the process of performing field trials using a mixture of late blight strains to test the effectiveness of the resistance gene.
This research relates to Objective 1, Develop adapted potato clones with enhanced resistance to major potato diseases.