Breeding wine grapes resistant to powdery and downy mildew
Du Plessis, H J
Vermeulen, A K
Daniels, E A
Van Schalkwyk, D
High production costs and a market increasingly driven by environmentally friendly production will lead to changes in grape cultivars planted in future. Though preventative spray programmes are effective to combat fungal diseases, they contribute to high production costs. An EU survey (2003) showed fungicide use in viticulture is considerably higher than in other crops. At the time more than 55% of plant protection products used in the EU were fungicides and about 70% of those fungicides were applied in viticulture, while grapevine accounted for only about 8% of the total crop production area. Eibach & Töpfer (2004) also estimated that total production costs (for wine grapes) in Germany could be decreased by up to 15,4% when a highly resistant cultivar was sprayed only twice a season instead of the normal regime of ten fungicide sprays. For a cultivar with medium resistance the costs could be lowered by up to 7,7% by using six sprays instead of ten. It is clear that growing cultivars resistant / tolerant to fungi can make a contribution in lowering production costs and may also address some concerns about fungicide residues in wine.
The aim ultimately is to breed new, high yielding cultivars, that will produce high quality wine, having resistance to downy and powdery mildew under local conditions. This will capitalise on the progress made at Agriculture Research Council (ARC) to breed disease resistant table grapes. Breeding for Botrytis tolerance will not be included in the initial stages of the project, but the potential of including it will be investigated.
Other aspects of relevance in the Western Cape, are the higher temperatures and lower rainfall foreseen in global warming models for this region and an increasing pressure on water supply for human consumption as opposed to agricultural use. Commercial cultivars adapted to warm climates, will be included in crosses to address the higher temperatures. However, rootstocks will be more appropriate to address drought resistance; for the moment breeding of new drought resistant rootstocks is not included in the spectrum of this project but will be considered in the future. The University of California Davis is driving a strong rootstock breeding programme and one of their focus points is drought resistance. Their breeding lines include plants collected in Arizona, Texas and California and Agricultural Research Council do not have access to these. It is also proposed that this project (should it be funded by industry) be used to secure Thrip funding for a separate project on drought resistance in collaboration with the University of Stellenbosch. Technology and or results of such a study could be incorporated in a breeding programme, should it be feasible.
1. Burger, P. 2014. Progress with breeding of downy and powdery mildew resistance. Presentation at the Winetech Pest and Disease Workshop. 23 September, Stellenbosch, South Africa.
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