Dr. M. Andrew Walke, geneticist and professor at the Viticulture and Enology Department of the University of California Davis, manages one of the most outstanding laboratories in the world specialized in the study of the genetics applied to the different diseases that affect the grapevine.
How the knowledge of the grapevine has evolved in the last years and what role has played on it the molecular techniques?
The sequencing of two forms of the Pinot noir genome has opened up many new approaches to answering genetic questions. As sequences are discovered in other species or cultivars they can be compared to the Pinot sequence and the sequences of other plant species so that guesses or approximations as to what the unknown sequences might control can be tested. It will also lead to advances in understanding and improving fruit characters such as aroma and flavor.
In many viticultural areas there is a trend for the recuperation of local varieties in order to make wine specific from the area. What is your opinion about this trend? Do you think consumers are “bored” about globalized grapes?
I am happy to see an interest in local / regional varieties and wines. I think it’s a shame for the wine industry to be dominated by a small set of “international varieties”
Sometimes we read that there are thousands of grape varieties. According to your studies what number of cultivated viniferas and wild (V. vinifera ssp. sylvestris) varieties may exist to know the genetic diversity of this species?
There are thousands of cultivated forms of vinifera (although many of what we once considered to be distinct varieties are in fact synonyms of clonal types). There remains a very rich diversity of varieties and an increasing interest in utilizing them. The issue of wild sylvestris populations is very interesting since many of these forms are feral cultivated types and seedlings. There are populations across Europe, North Africa and the Middle East but all are at risk from agricultural development, diseases and pests.
Is there some way to preserve the genetic variability? How many varieties can be disappeared?
The cultivars need to be preserved in repositories at several locations - both regional and national. Their genetic diversity is being studied but they also need to be preserved and have their viticultural attributes characterized.
The molecular studies and grapevine sequencing, do you think are crucial to establish future directions towards the study of resistances to diseases? Do you think we have to consider GMO to control classical diseases like downy mildew or powdery mildew?
Advances in molecular genetics have allowed the use of molecular breeding based on the DNA markers associated with traits such as disease and pest resistance. This allows the screening of seedlings at a very young age and identifying those with the traits of interest so that time, effort and space can be allocated only to individuals with those traits (which greatly expedites breeding progress. These markers are based on genetic mapping studies. These mapping efforts also identify the genes responsible for these traits (first as statistical associations and later as physical locations I the genome). Once the genes are located they can be extracted and engineered into grape varieties. We can control mildew diseases with classical breeding in association with DNA marker-assisted selection and do so at a relatively rapid pace. The acceptance of these new hybrid varieties will depend upon public demands on the use of fungicides and/or their restriction. GM approaches can also be approached but will be complicated by what are usually very complex interactions among genes and their expression and public willingness to accept GM grape varieties.
In some countries there is a drop in wine consumption. Do you think we can put into value some local or traditional varieties? How we can use their maximum potential?
The local/traditional varieties have historical and enological value. They must be preserved but may or may not play a large role in grape improvement. I think these issues are more socioeconomic rather than viticultural or genetic.
Your research is more into grapes with low input of pesticides. In how many years do you think it will be available for commercial use?
My set of new rootstocks with very broad and durable nematode resistance (also phylloxera resistant) are available now. We have advanced selections of Pierce’s disease resistant grapes that are 94% vinifera and could be commercialized now, although the seeds of the 97% vinifera are the ones we are moving towards commercializing. We are also moving ahead on powdery mildew resistant varieties that will be introgressed into the Pierce’s disease resistant selections. I hope these wine grapes will be in commercial trials within 5 years, but adoption will depend on the intensity of disease and public interest.