Breeding for durable resistance is an objective of most plant breeding programmes. In apple, scab is a major disease worldwide and the Venturia inaequalis-Malus pathosystem provides a good model system to study the durability of resistance. The biology and adaptation rate of the pathogen pose a moderate to high risk (Linde and MacDonald, 2002) to apple breeding programmes achieving durable resistance. A number of virulent Venturia inaequalis pathotypes have been identified since resistance breeding started in earnest over 60 years ago, but the knowledge about their emergence and distribution in the pathogen population at large remains anecdotal to date. Such information is of critical importance in order to breed new cultivars with durable resistances. This project aims to introduce the monitoring of Venturia inaequaliss virulences in different populations on a regular basis as is commonly done for the major diseases, such as rusts, in the cereals (Mesterházy et al. 2000). The findings of this research will assist breeders in determining which (combinations of) scab resistance genes to employ in breeding strategies based on gene pyramiding.

There are two basic requirements to successfully reach this goal:

1. Co-ordinate the systematic collection of data on the distributions of virulent Venturia inaequalis populations CLICK

A set of differential hosts has been identified for the monitoring of Venturia inaequalis populations in the orchard. The set will be extended as new gene-for-gene relationships are defined and appropriate hosts have been identified.

2. An effective nomenclature system based on well-defined host-pathogen interactions in the Venturia inaequalis-Malus pathosystem CLICK

The current nomenclature system has proved to be unsuitable for the naming of Venturia inaequalis races. It therefore was modified to provide the flexibility required to accommodate the many and variable combinations expected in the highly heterogeneous populations of the apple scab fungus. The basic premise of the new system is that a specific number is assigned to each single gene-for-gene relationship.

Initiator and coordinator of the part of the project "monitoring of Venturia inaequalis virulences"project:
Dr. Andrea Patocchi, Agroscope (Switzerland) [right in picture]

Initiator and coordinator of the part of the project "Nomenclature of Venturia inaequalis races":
Dr. Vincent Bus, Plant & Food Research (New Zealand) [left in picture]

last update: 11th March 2024