Identification and characterisation of the Avr effectorgenes in Puccinia horiana

General introduction

Chrysanthemum rust is caused by the fungus Puccinia horiana. Due to the declining availability of approved fungicides, control of this disease must increasingly rely on resistance breeding. Breeders, the best of whom are located in Flanders and the Netherlands, must take into account the presence of various pathotypes within P. horiana. Pathotypes are variants that cause disease in some chrysanthemum cultivars but not in others. This project focuses on identifying the underlying genes of these pathotypes, namely the avirulence effector genes. Their identification will later allow for the rapid characterization of existing and new pathotypes of this fungus, ultimately enabling more targeted and sustainable resistance in the breeding of potted and cut chrysanthemums.

Research approach

The ILVO collection of P. horiana isolates will be expanded with potentially relevant isolates. The pathotype of these isolates will be determined by screening a diverse set of cultivars, including both mums and cut chrysanthemums. Pure DNA will be prepared from collected basidiospores of the relevant isolates, which will then be used to determine the complete genome sequence of the isolates. The study and comparison of these genomes should allow for the identification of candidate effector genes. The most promising candidate effector genes will be characterized.

Relevance/Valorisation

Chrysanthemum rust is the most important disease affecting both mums and cut chrysanthemums. Mums have traditionally been important to Flanders, home to leading breeding companies. Cut chrysanthemums are the second most important cut flower worldwide (after roses, closely followed by carnations), with a market value of approximately €5 billion. Breeding for these plants is primarily located in the Netherlands.

The results will primarily be shared with the leading breeders of mums and cut chrysanthemums in Flanders and the Netherlands. They are uniquely positioned to implement the results directly into their breeding programs. The project includes a doctoral program, which will also allow scientific results to be disseminated through publications. There is a possibility that some of the results can be translated to other fungal rusts, such as the important grain rusts.