Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/20/2001
Publication Date: 4/1/2002
Citation: Magee, J.B., Smith, B.J., Rimando, A.M. 2002. Resveratrol content of muscadine berries is affected by disease control spray program. Hortscience. 37:358-361
Interpretive Summary: Muscadine grapes are enjoying a resurgence of grower and consumer interest because recent research has shown they contain resveratrol, a plant component which may prove beneficial in nutritional and chemopreventative treatment of cardiovascular disease and cancer. While control of muscadine diseases is necessary for maximum yield and highest berry quality, muscadines produce resveratrol in response to disease challenge or other stress. The objectives of the study were to evaluate the effects of a systematic fungicide spray program on foliage and berry diseases and to study the relationship between disease incidence and resveratrol content of the berries. Fungicides applied to five cultivars at 10- to 20-day intervals from early bloom until just before harvest significantly reduced all fungal foliage and berry diseases. Sprayed berries had lower disease scores, fewer inedibles and more symptom-free berries than the unsprayed controls, indicating higher fresh-market quality. These results are important to the grower because they show that the season- long fungicide spray program used will yield a higher quality muscadine. Resveratrol levels, a desirable attribute, varied by cultivar but, overall, were lower in sprayed berries. The relationships between specific berry diseases and resveratrol content were not established, results important to research workers studying resistance to muscadine diseases and the affects of cultural practices on resveratrol production.
Technical Abstract: Control of muscadine diseases is necessary to minimize yield loss and is especially important for highest quality fresh-market berries. In a systematic disease control spray program, four fungicides registered for use on grapes were applied sequentially at 10 to 20 day intervals from early bloom until just before harvest to five muscadine cultivars. The objectives of the study were to determine the effects of the spray schedule on foliage and berry diseases and to study the relationship between disease incidence and resveratrol content of the berries. Foliar diseases were rated visually twice during the season, and berry disease ratings were made at harvest. All fungal foliage and berry diseases were significantly reduced by fungicide treatments. Resveratrol was determined separately on berry skins, seed and pulp/juice by GC/MS. Overall, resveratrol levels in berry skins from unsprayed vines were much higher than those of sprayed vines. Concentrations varied by cultivar and within cultivar by treatment. The relationship between resveratrol concentration in skins and total disease score or scores of specific diseases was not established. Seed resveratrol concentrations differed by cultivar but were not affected by the fungicide treatments. Resveratrol concentration of seed was lower than that of skins. Accumulation of resveratrol in juice/pulp was much lower than in skins and seeds.