Fan leaf virus is spread by nematodes and stunts the growth of the vines, seriously affecting yield. The virus is spread by a specific nematode and, with the demise of soil sterilants in the wine grape industry, populations have been building up significantly in areas where continual wine grape production takes place. 

Pierce Disease (PD) is a type of Xylella affecting wine grapes. It’s had a presence in the Balearics for some time and has now made it to mainland Europe.

Fortunately, Dr Andy Walker at the University of California, Davis, had the foresight to predict these problems and channelled some of his plant breeding efforts accordingly.

GPG represents UC Davis for both the rootstocks and the PD resistant wine grape varieties so with that in mind, Claire Donkin and Rupert Hargreaves visited with some vineyards and grapevine nurseries along with Guillaume Mercier from Mercier’s Nursery in France.

The visit to the Ojai Vineyard owned by Adam Tolmach in Southern California proved extremely beneficial, as all were able to see the vine production and learn of the different growing techniques and experiences per variety plus of course, trying the wines. Here, they tried 3 out of the 5 new varieties, namely Paseante Noir, Caminante Blanc and Ambulo Blanc.

The Paseante Noir was extremely impressive.  It is deep red in colour with great floral qualities in the aroma. The alcohol content was 13%, impressive to be on the lighter side of the alcohol range for a dark/deep red wine. The vines were extremely high yielding too which is encouraging.

Caminante Blanc produced an aromatic white wine being comparable to Sauvignon Blanc with a hint of Gewurtraminer. Once again, it has large yields and produced a wine with 12% alcohol content.

Ambulo Blanc has a Chardonnay/Sauvignon Blanc flavour profile. At this particular vineyard, they had a smaller area of this grape variety and were using it successfully in blends.

Visits were also made to leading grape vine nurseries Wonderful and Sunridge. As we all know, there is no substitute to visiting likeminded companies and getting grower to grower discussions taking place to achieve common goals. These visits proved hugely beneficial to all parties to understand and debate the best techniques to improve callusing and grafting of the GRN rootstocks.

The timing of the trip was important to make sure that GPG and our nursery partners are moving as fast as we can to have enough plant material being tested in advance of the 2 potential devastating problems affecting the wine industry. The first trials of the GRNs have now been planted in the Champagne region of France so we will soon have indications on their ability to control the nematodes and also their adaptability to the limestone soils.

The highlight of the trip over and above the practical knowledge discussed and shared, was the Paseante Noir. We feel this variety has a place in the wine industry almost irrespective of the fact that it happens to be PD resistant too.

The next 2 years will be hugely exciting for Claire and the team to trial and test these further with Mercier and Provedo in Spain.