Background/context:

Members of the genus Phytophthora infect a wide range of plants and cause extensive economic losses and environmental damage worldwide. The range of fungicides that target Phytophthora (members of the Oomycetes, and thus not true fungi) is limited, and the effectiveness of both plant resistance and the fungicides currently in use can be lost rapidly as the pathogen evolves. 

Avirulence genes are believed to encode proteins that are important for pathogen growth and infection. However, resistant plants are able to recognise the direct or indirect products of these avirulence genes and rapidly mount a defence response. An understanding of the nature of avirulence proteins and their functional domains will be a major breakthrough which will allow identification of plant receptors responsible for pathogen detection and development of novel strategies for durable disease resistance.

 Aim:

The goal of this sub-project was to identify and characterise Phytophthora genes responsible for pathogen avirulence and pathogenicity with a view to providing knowledge basic to the development of improved control measures.

Major Outcomes:

Over 200 genes expressed in zoospores of Phytophthora nicotianae have been isolated and partially sequenced. A selection of these genes likely to be important for pathogenicity have been characterised in detail, including localisation and transformation studies to determine gene function and role in infection. 

It is disappointing to report that we have been unable to identify and confirm the gene(s) that control the Avr4/6 phenotype in thePhytophthora sojae genome, despite some exciting initial results. Stable transformation of P. sojae is highly erratic worldwide, and we are collaborating with Prof. Brett Tyler whose group has recently been successful with this technique, and we will continue to test selected candidate genes in his laboratory.

For more information contact:

Prof Adrienne Hardham
Australian National University
Phone: +61 (0)2 6125 4168
Email: Adrienne.Hardham@anu.edu.au

or

A/Prof Don Maclean
The University of Queensland
Phone: +61 (0)7 3365 2387
Email: d.maclean@uq.edu.au