The Cantu lab just published a paper that describes, for the first time, the genome of grape powdery mildew and its evolution in relation to fungicide resistance. 
In addition to providing the first description of the large and highly repetitive genome of Erysiphe necator (causal agent of grape powdery mildew), this work shows that frequent structural variations occur between field isolates, including copy number variation (CNV) in EnCYP51, the target of sterol demethylase inhibitor fungicides. 
The authors demonstrate that CNV of the EnCYP51 gene contributes to E. necator fitness by providing increasing quantitative protection against DMI fungicide treatments in a gene-dosage dependent manner. 
Monitoring powdery mildew evolution for the development of fungicide resistance should include measuring the number of the EnCYP51 gene copies. This knowledge will help in managing fungicide programs and maintaining effective control of powdery mildew while minimizing the development of populations increasingly resistant to DMI treatments. 
The results of this work not only demonstrate the effectiveness of using genomics to dissect complex traits in organisms with very limited molecular information, but also may have broader implications for understanding genomic dynamics in response to strong selective pressure in other pathogens (not only of plants) with similar genome architectures.
Laura Jones, Summaira Riaz, Abraham Morales-Cruz, Katherine CH Amrine,Brianna McGuire, W Douglas Gubler, M Andrew Walker and Dario Cantu; BMC Genomics 2014, 15:1081