Researchers are one step closer to discovering the nation’s top mildew resistant vines.
After five seasons – and an original field of 1200 downy and powdery mildew resistant vines – a CSIRO team has narrowed the field to 20 red and 20 white berried ‘superior’ vines that are capable of fostering a range of wine styles and flavour and aroma profiles.
Now, a series of regional field trials will be conducted to evaluate these selections and determine the best performing vines under a range of Australian viticultural climate conditions.
‘Put simply, we are seeking superior vines that not only produce unique wines with robust flavour styles – but, because they need less spraying, are more environmentally friendly and also have lower input costs’, said lead researcher, CSIRO’s Mark Thomas.
Dr Thomas said there was a global movement towards reducing chemicals applied to crops, including grapevines, and research groups in the European Union, Chile and United States of America were already breeding new mildew resistant grapevine varieties.
‘It’s important that Australia keeps up with this research too.’
To this end, Dr Thomas’ recently completed project – supported by Wine Australia – was Australia’s first large-scale screening of mildew resistant vines.
The 1200 young seedlings were screened in a glasshouse using unique DNA markers developed by the research team. The technique enabled rapid breeding and evaluation of plants at the screening stage, to select for those seedlings with disease resistance, desired berry colour and muscat flavour, before planting in the field.
Only individuals that had the desired combination of traits were planted in the field for evaluation of plant performance (e.g. yield) and wine quality.
Small-scale winemaking methods were then developed for single vines of both red and white berry selections and the wines were screened using wine chemistry and a sensory panel of winemakers and researchers.
Dr Thomas said red wines favoured by the panel had high colour and a diversity of flavours that ranged from those commonly associated with Cabernet Sauvignon to Shiraz.
‘The highly coloured wines had red flesh parentage, and these were found to also have high antioxidant potential’, he said.
The white wines most favoured by the sensory panel were aromatic and floral and an examination of the parentage of these selections showed that they had a Muscat or Riesling parent.
Lower alcohol wines were also made from selected red and white berried vines by harvesting early at low sugar levels. The objective was to see if it was possible to make attractive lower alcohol styles without the need for additional manipulations in the winery. The sensory results indicated that the reds showed the most promise.
Dr Thomas said the next phase of the research was to develop the second generation of mildew resistant vines that have additional genes for both downy and powdery mildew resistance – allowing them to produce vines that have stronger and more durable resistance.
Four regional field sites that cover the main climates where grapes are grown (cool to warm irrigated) have been established in the Barossa Valley, Irymple, Riverina, and Orange.
Dr Thomas said the research was not only important for growers, but for the wine sector as a whole.
‘Adoption of new varieties that have resistance to downy and powdery mildews will not only reduce management input costs for growers through reduced spraying during the season, but they will be more environmentally friendly.’
The final report from the initial project can be found here.
Dr Mark Thomas' recently completed project was Australia's first large-scale screening of mildew resistant vines.