Endodormancy in Apple

Management Techniques in Southern Uruguay

Abstract

Chemical rest breaking agents to compensate chilling requirements in apple (Malus domestica Borkh) are widely used in Uruguay (34º 37’ SL). This study evaluated the response to the application of rest breaking products in two varieties (Red Chief and Granny Smith), in three moments (AT), during 2005 and 2006. Treatments were evaluated in a factorial arrangement with two factors, product and moment. Products evaluated were: Hydrogen Cyanamide (2.5%), mineral paraffinic oil (3%), refined paraffinic mineral oil (2%) and a mixture of Hydrogen Cyanamide (0.75%) and paraffinic mineral oil (2%). The first application was performed at 250 CU (UTAH model) (during the first 15 days of August), and the following the first and third week of September. Beginning of the endodormancy release was determined when 50% of leaf fell, and completion was defined when 50% of one year old buds sprouted in a grow chamber. Budbreak percentage under field conditions was evaluated weekly, and new shoot length was quantified. At harvest, flesh firmness, soluble solids and starch content were measured. For most cases, ‘AT x product’ interaction and ‘product’ effect on budbreak percentage were not significant, while ‘AT’ effect was significant. Chemical products applied at the second and third AT significantly increased budbreak percentage with respect to control, while products applied first triggered earlier budbreak.