The aim of this project is to breed second generation mildew-resistant scions combining powdery mildew and downy mildew resistance genes from different wild genotypes to further enhance the durability of these new selections in the vineyard.
Through earlier Wine Australia projects, new sources of genetic resistance were identified to both powdery and downy mildew from wild Chinese Vitis species and these have been introgressed into a V. vinifera microvine background in preparation for crossing with selected elite first generation selections to produce second generation disease-resistant varieties combining resistance loci from two different genetic sources.
The project will carry out crosses between V. vinifera microvine progeny containing new resistance loci for powdery and downy mildew with selected first-generation disease-resistant progeny containing Run1 and Rpv1. The resultant seed will be screened at the seedling stage, using DNA markers, to identify progeny that will produce perfect flowers (fruit) and that carry two powdery mildew and two downy mildew resistance loci. These plants will be transferred to the field and screened over many seasons for vine performance including yield and fruit (wine) quality.
The next stage will develop microvine breeding lines containing two powdery mildew and two downy mildew resistance genes in the homozygous state that can be used for the future generation of third generation scions in which disease-resistance traits are combined with desirable consumer traits (project CSA 1701-1.2). Having all four resistance loci in the homozygous state in one of the parental lines will ensure that all progeny generated using this parent will contain all four resistance loci and allow us to undertake selection for progeny containing desirable consumer traits.
The tools and genetic resources generated from this project will form the foundation of future germplasm improvement for the Australian wine sector over the next 20–30 years.