Identification and marker-assisted selection of genes for reducing the susceptibility of new winegrape cultivars to fungal pathogens

Summary

Objectives

To identify  new fungal resistance genes and genes associated with open bunches which can be pyramided with the two existing genes for fungal resistance to  provide durable mildew resistance in the vineyard.

Background

Previous work has developed mildew resistance in grapevines through conventional breeding by incorporating genes from other Vitis species into V. vinifera. These new grapevines are currently undergoing field trials. Experience in other crops indicates that once resistant germplasm is used on a large scale there is a real risk of the resistance failing as a result of the emergence of new virulent isolates. One way to keep a step ahead of this is to develop second generation mildew-resistant varieties that contain multiple and additional powdery and downy mildew resistance genes from different sources. This pyramiding of multiple resistance genes significantly increases the durability of resistance genes in the field.

There are no known resistance genes for botrytis bunch rot in any plant. This is because Botrytis colonises already dead tissues (it’s a necrophyte). For grapevines it is known that open clusters reduce susceptibility to bunch rot e.g., tight bunch cv. Zinfandel is very prone to botrytis bunch rot, while the Primitivo clones of Zinfandel with looser bunches are not as prone to bunch rot.

Research approach

The project addresses both mildew resistance and reduced susceptibility to botrytis bunch rot. Genes already known to confer mildew resistance in other Vitis species will be assessed. The micro-vine will be used to move these non-vinifera resistance genes into a vinifera background to produce a second generation of selections to complement those that have already been produced. For botrytis bunch rot, markers associated with open clusters will be identified and mapped over two seasons with existing grapevine populations. These confirmed markers would then be available for breeding in future.

Industry benefit

The knowledge, markers and the new breeding material developed in this project will allow grapevine breeders to reduce bunch rot susceptibility and produce the second generation of mildew resistant grapevine varieties in the future. This will give grape growers and winemakers access to planting material with desirable viticultural properties; and through this, the ability to optimise production efficiency.