The response of grapevines to methanol was investigated at the Orchard Mesa Research Center in Grand Junction, CO. Optimum sublethal methanol dose levels, based on visual assessments, were 90% for leaves and 100% for trunks for 10 cultivars. Total soluble sugars (TSS) of the berries, monitored every week until harvest, showed significant differences with Muscat Blanc during veraison. Berries from the methanol-treated vines had higher TSS (16.4 °Brix) than controls (15 °Brix). However, no significant differences were observed later in the season when approaching fruit maturity. At harvest, data on yields as estimated by cluster weight, berry weight and berry size showed no differences between the two treatments. Methanol did not enhance cold hardiness of bud tissues. measured by differential thermal analysis. It was concluded that, although methanol has been reported to improve several physiological features of C3 crops, our study suggested that it has little or no practical effect on grapes. More data on the determination of sugars in berries by HPLC will be discussed.
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