Understanding the basis of agrochemical resistance in biotrophic grapevine pathogens

Summary

Objective

• Improving understanding of agrochemical resistance in powdery mildew
• To determine the genetic basis for metalaxyl resistance in downy mildew

Background

The development of resistance to agrochemicals is an ever-increasing problem in agriculture, and one for which the Australian wine sector is not immune. Results of a recent SARDI/AWRI research project have shown that there is widespread prevalence of known resistance alleles to many of the commonly used agrochemicals in the main biotrophic grapevine pathogens Erysiphe necator (powdery mildew) and Plasmopara viticola (downy mildew).

While the molecular basis of resistance is well known for many agrochemicals, there remain agrochemicals for which targets are not known. There are key agrochemicals, such as metalaxyl (the key control measure for downy mildew) for which field resistance is readily observed but the genetic cause (and therefore a genetic test for resistance) is unavailable.

Research approach

This project aims to use genome sequencing technology to determine the genetic basis for resistance of Plasmopara viticola (downy mildew) to metalaxyl, providing the means to design a simple genetic test for the presence of field resistance.

The AWRI will be responsible for isolating and obtaining genomic DNA from phenotyped downy mildew isolates so that whole genome sequencing and assembly may be performed.  Genome sequencing approaches and metagenomics will be explored for subsequent population analysis of trunk disease isolates, in collaboration with the SARDI-led project, ‘Grapevine trunk disease management for vineyard longevity in diverse climates in Australia’.

Sector benefits

The new knowledge generated, and tools developed, will improve grapegrowers’ ability to manage one of the most economically important diseases in Australian viticulture, powdery mildew, caused by Erysiphe necator.