Renewed interest in breeding disease-resistant vines

A collaborative project under way in Riverina began in South Australia half a decade ago and has roots dating back to 19th century France. But for Dr Mark Thomas, it represents the way of the future.

With CSIRO colleagues, he has bred around 8000 new grape varieties over the past 5 or 6 years, all of them hybrids of European (vinifera) and American species, to identify those that are resistant to the diseases that plague so many vineyards, powdery mildew and downy mildew.

That’s what they did with great success in France in the late 1800s, to the extent that by the 1950s nearly half of all French vineyards were planted to clever new French hybrids resistant to phylloxera and mildews. However, wine politics and economics then intervened through appellation (AOC) regulations, first introduced in 1935 and that limited the use of hybrids, and the sector returned to old varieties on rootstocks that had to be sprayed regularly.

But things are changing again. Whether motivated by a desire to cut costs, be kinder to the environment or both, most wine producing nations are looking to again breed disease-resistant varieties. However, there are two big differences between then and now.

The first is the advent of DNA technology, which allowed Dr Thomas to quickly assess the potential of his 8000 varieties and cull them back to a more workable 1200 for testing in the field. ‘What we did in the glass house was get a lot of crosses, germinate the seed and at the three-leaf stage of the seedling extract DNA from a leaf’, he said. ‘Using DNA markers we were able to say if a seedling was resistant and whether it would have white berries or red.’

The second change is a greater focus on breeding with material that had been through many rounds of breeding back to vinifera. ‘Our work is focused on trying to do a lot of back crossing to vinifera so that essentially what we end up putting into the field has over 90 per cent vinifera DNA. If you look at it, you can’t distinguish it from a normal vinifera vine. The idea is to do the breeding and the DNA marker work so that we end up with essentially a vinifera vine with a little bit of DNA that contains the resistance genes.’

The next step was to identify the 40 mildew-resistant selections with the greatest potential (20 reds and 20 whites) from the 1200 and to start to test not only how they perform in different regions, but also what sort of wine they produce.

The first move away from the Barossa was to the National Wine and Grape Industry Centre (NWGIC) in Wagga Wagga, where CSIRO and the NSW Department of Primary Industries set up an evaluation and demonstration site in 2014. Vine growth, berry parameters and water-use efficiency are being closely monitored and the first white wines will be produced from the fruit in the NWGIC experimental winery in the coming vintage.

Progress to date will be reported at a seminar and field day looking at major grape diseases to be held at the NWGIC on Wednesday 16 November. [For information and registration contact rharrington@csu.edu.au]

‘We really want to engage with local growers and winemakers and to get them involved with tasting and evaluating the wines that these varieties can produce in their region’, Dr Thomas said.

‘There’s a lot of interest in the project, but proving that it works and can save money is only the first step. For the sector there is the issue of how long it would take to start growing and using these varieties, what they would call them and how they would be marketed.’ An initial adoption pathway might be in blends to provide better colour or flavour to existing variety labels or non-variety labels.

The CSIRO already plans to set up a second trial site on its own vineyards in Irymple and Dr Thomas hopes to establish at least one other in the near future, ideally in a cool climate region. His ultimate aim is for regional trials to become the norm for wine grapes, as they are for many other crops. ‘In any other crop the breeding will be done at one site and then new selections will go to regional sites for evaluation. That is how we need to approach things.’

‘We are breeding new varieties and we think that’s the best thing for the sector if they’ve got a problem with disease, or nematodes, or salt, or simply are trying to improve wine quality’, he said. ‘Breeding can make the big step changes rather than the smaller incremental changes that are possible with management improvements.’