Plant breeding for organic and sustainable, low-input agriculture

Genotypic variation of attack degree (AD%) with downy mildew
(Plasmopara viticola Berk & Curt) in six grape varieties, under chemical and organic
control treatments
Claudiu Bunea, Marin Ardelean,
University of Agricultural Sciences and Veterinary Medicine, Cluj-Napoca, Romania
Six grape varieties (three domestic and three foreign) destined for wine production (Aromat de
Iaşi, Pink Traminer, Italian Riesling, Fetească Regală, Muscat Ottonel, Blasius) were tested in
2006, in Gherla, Cluj county, Romania, concerning their level of attack degree (AD%) with
downy mildew (Plasmopara viticola Berk & Curt) under two types of control treatments:
chemical and organic. Two treatments were applied both in the chemical and organic variants of
control. The chemical treatments consisted in SHAVIT 72 WP, 0.2%, before flowering stage,
and Curzate Manox 0.25% between flowering and green grape berry stages while the organic
treatments consisted in Bordeaux mixture 0.5% + purine of greater nettle 1/20 dilution, before
flowering and Bordeaux mixture 0.75% + soluble sulfur 0,4% between flowering and green
grape berry stages. There resulted a trifactorial experiment (types of treatments, genotype and
number of treatment) with a total number of 24 variants.
Both variety, type of treatment, number of treatments and two simple interactions (type of
treatment × variety and type of treatment × number of treatments) showed significant effects on
AD% level while the triple interaction (type of treatment × variety × number of treatments)
proved nonsignificant. The lowest AD% level was registered in Aromat de Iaşi and Pink
Traminer varieties (AD% = 1.08) while the highest AD% was found in Italian Riesling (3.07%),
the intervarietal coefficient of variability for this character being rather high (32.6). These results
are in total agreement with previous data published by other authors (Husfeld, 1962; Zăvoi,
1979; Deacon & Berry, 1993; Cheregi, 2003) who found an impressing intervarietal variability
of AD% level among different grape varieties, both under natural or/and artificial inoculation
with downy mildew. The general effects of chemical treatments were slightly better than those
of the organic ones as far as the AD% was concerned (1.47% vs. 2.11%), but it must be
emphasized the fact that in the least sensitive varieties (Aromat de Iaşi and Pink Traminer) the
AD% level was, practically, identical both under chemical and organic treatments. These results
are of great interest since such varieties seem to be better adapted to organic control practices of
downy mildew and, conseqeuently, are recommended for organic grapeyards and, on the other
hand, they could prove as valuable genitors in creating new grape varieties adapted to organic
control of downy mildew.
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