Effects of Dormex (Hydrogen Cyanamide) on the performance of three seedless table grape cultivars grown under greenhouse or open - field conditions

ArticleGreenhouse cultivation of table grapes is still limited to some experimental trials at Lebanese coast. One major constraint facing this type of cultivation is the lack of enough chilling hours causing irregular bud - break and yield reductions. Dormex, with Hydrogen Cyanamide as active ingredient, is an effective mean for dormancy release adopted in warm winter regions. The work investigated separate and combined effects of two factors: greenhouse cultivation and Dormex application on vine buds (following win ter pruning) on three - year old seedless cultivars (ARRA15, ARRA18, and ARRA19). Control consisted of non - treated plants grown in open - field. Results showed that Dormex application under greenhouse induced budburst uniformity, increased budburst percent (by 60%), number of flowers and fruits per shoot (by 83%) and vine productivity (by 90%) in all cultivars compared to control. Bud formation was increased under greenhouse and was reduced by Dormex treatment. Under greenhouse, elongation of current season sho ots was delayed and shoot length was reduced in treated plants, harvest was earlier by 7, 14, and 30 days in non - treated plants of ARRA18, ARRA19 and ARRA15 respectively and full fruit set (100%) occurred for all plants. Dry weight of shoots was improved b y Dormex application in both cultivation systems. All ARRA cultivars responded similarly to experimental factors except ARRA 19 under greenhouse where shoot length was enhanced in all plants while bud formation only in treated plants. Finally, treating vin e by Dormex under greenhouse was found as efficient tool to improve bud break and advance harvest under the specific Lebanese coastal conditions