Grape powdery mildew now has sex
Sexual state of grape powdery mildew (Jerry Cooper).
Powdery mildew disease of grapes has been present in New Zealand in asexual form for over 100 years. In 2013/14, the sexual stage was found for the first time in Hawke’s Bay, a discovery that coincided with a season in which disease control proved particularly difficult.
Having both sexual and asexual spores means that there is greater opportunity for the fungus to infect its host, and sexual populations tend to be more pathogenic and more prone to developing fungicide resistance.
Our preliminary genetic characterisation of the fungus in New Zealand indicates there are three genetically distinct populations, with one population consistently linked to difficult-to-control outbreaks of the disease. Further research and a much wider sampling programme will determine the geographic distribution of the different genotypes, and clarify whether there is a consistent relationship between sex and disease virulence. These basic data will underpin development of effective control strategies for powdery mildew to ensure the future viability and profitability of the multimillion-dollar viticulture industry.