Biodynamics and Yeast Biodiversity
Does biodynamic viticulture really make a difference to the vineyard? Over the years I’ve asked this question of several vignerons who have undergone the conversion from organic to biodynamic methods and comments on the apparently increased health of the vines have been common. Reports included more vigorous growth, deeper greener colours, thicker stems and so on (one such report came from Eddy Oosterlinck of Domaine de Juchepie, pictured below); how valid these observations are, made in unblinded fashion, comparing the current season’s growth with the memory of the previous year’s, however, is certainly open to question. And what about the microbial life? It’s easy to look at the rich, grassy and floral carpets seen in the organic or biodynamic vineyard and imagine that the soils are full of healthy and happy organisms, especially when they are compared with the scorched-earth vineyards of some chemically-managed estates. Orange grass never inspires confidence, does it? But is there any evidence to support a conclusion that one vineyard really is more ‘healthy’ than another?
Well, I can’t say I’m particularly well read in this area, but a recent paper published in PLOS ONE, from Setati et al at the Stellenbosch Institute for Wine Biotechnology, seems to throw some light on the matter. Methodologically, it looks like a sound study, although I would suggest that such judgements are really only valid coming from someone with a knowledge of the literature; this knowledge allows you to look at a paper with a more critical eye, rather than just believing, which is a common problem when journalists read research papers I find. With my lack of credentials firmly established and accepted, I still think this is a valid and interesting paper (link at the bottom of the page).
The study involved three vineyards, managed in three fashions: (1) biodynamic, (2) conventional and (3) integrated production. Vineyards (1) and (2) were managed as you would expect, whereas vineyard (3) was a sort of ‘half-way house’ site, where some chemicals were used, but alongside some less conventional methods including cover crops, chicken manure and soil inoculation. Samples of grapes from the three sites were taken to see how the microbial flora living on the fruit differed across the three sites. Samples were taken from numerous spots within each vineyard, and they were analysed using not just cultural methods (i.e. seeing which yeasts and other organisms grew when washings from the samples were plated out on suitable growth media) but also using molecular techniques. These fancy molecular techniques looked at the DNA (well, RNA to be pedantic, but that’s not important right now, and you get the idea) of the ribosome, a structure which not only allows typing of the organism but also allows you to see how closely a group of said organisms are related.
The results were interesting on many levels. Before coming to the biodynamic differences, the authors pointed out that (a) there was some variation within vineyards, from one row to the next, and (b) the modern molecular methods identified more species than the older cultural methods. Both findings are relevant to researchers in the area as it means (a) previous studies where sampling has been limited may be flawed because of the small sampling technique – you need to examine multiple spots within each vineyard to get a true picture, and (b) older studies using cultural and not molecular methods will have presented only a partial picture of the organisms living in the field of study.
These findings are important, but it is the biodynamic differences the team identified that were the most interesting part of the results I think. Firstly, there was certainly more diversity in the organisms identified in the biodynamic vineyard. As an example, one species – Aureobasidium – accounted for 70% of all isolates in the conventional site, 63% in the integrated site, but only 53% in the biodynamic site. Many organisms were only seen in the biodynamic site; admittedly many were seen in the conventional/integrated sites and were not in the biodynamic site, so this doesn’t really prove anything, it is more the overall diversity that is of interest.
Some species identified, such as Sporisorium, which was in the biodynamic vineyard but not the others, have never been picked up in vineyards before; this at first glance seems heart-warming, but we must bear in mind that the new molecular methods might be responsible rather than this being a result of biodynamics. Of greater interest, though, is the fact that several species identified in the biodynamic vineyard but not in the other two are of potential benefit to the vines. Meira geulakonigii and Rhodosporidium diobovatum, both living in the biodynamic vineyard studied, have active biocontrol capabilities. Meira geulakonigii is active against spider mite and rust mite, with the mites suffering 100% mortality when exposed, whereas Rhodosporidium diobovatum is active against Botrytis cinerea, which might be famous and welcome for its effect in Sauternes but in most vineyards would be regarded as a pest, causing harmful grey rot.
Clearly the study only reveals the tip of the iceberg, and there is huge scope for further work here. Nevertheless, even taken in isolation, this study seems important; biodynamics improves microbial diversity, and these more diverse species may be active against pests and rot, and thus be of benefit to the vine. None of this necessarily translates through to increased quality in the final wine though; I suspect research in that area will be fraught with confounding variables (although there should be no shortage of willing test subjects!).
Link to the paper: The Vineyard Yeast Microbiome, a Mixed Model Microbial Map