Identification of Apple Tree Varieties with Greater Adaptation to Freezing Stress
Principal Investigator: Renae Moran (UMaine, Highmoor Farm/School of Food and Agriculture)
Partners: Bryan Peterson (UMaine, School of Food and Agriculture)
Abstract: Cold temperature (freezing) injury occurs throughout temperate climates in which fruit crops are grown and causes extensive losses for fruit growers. Damage from freezing temperatures impacts the industry through reduced yield and fruit quality, greater susceptibility to canker diseases and insect pests, and high costs of tree replacement. Through this project, we will increase the survival of trees in apple orchards and profitability for apple growers as they adopt improved rootstocks. We will measure cold temperature tolerance in several important new rootstock varieties, G.214, G.4011, G.4814, G.935, V.6, G.41 and M.9. Trees for this project will be grown and acclimated to cold at Highmoor Farm, Monmouth, and lab work will be conducted at the University of Maine, Orono. Using a controlled programmable freezer, freezing tolerance to temperatures of 0 to -40C will be measured in 2-year-old shoot pieces during two periods of the season. Hardiness will be evaluated from early September to early December at 14-day intervals or until maximum hardiness occurs to determine which varieties are the first to become hardy. The rate and degree of hardiness loss will be evaluated in mid-March in shoot pieces held at 20C for 0, 2 and 4 days. The student will be asked to present results of the fall hardiness measurements at the Maine Ag. Trades Show in Jan. 2018 or at the University of Maine Research Expo in 2018. These results will directly inform growers who are selecting new rootstocks for apple production in Maine’s climate.