Effect of Dwarfing Rootstocks on Low Temperature Tolerance of ‘Golden Delicious’ Apple Trees During Winter 2008-2009

Abstract

Winter injury can significantly reduce apple production, particularly in areas subjected to dramatic freeze-thaw cycles. The responses of ‘Golden Delicious’ apple trees on 11 rootstocks, during freeze-thaw cycling that occurred during the winter of 2008-2009 in Georgia, were investigated in an orchard trial of apple [ Malus× sylvestris(L.) var. domestica(Borkh.) Mansf.] dwarf rootstocks that had been established at the Georgia Mountain Research and Education Center in Blairsville, GA in 2003 with the Gibson strain of ‘Golden Delicious’ as the scion. It was one location of the larger 2003 NC-140 Dwarf Apple Rootstock Trial. The four rootstocks Malling 26 EMLA (M.26 EMLA), Budagovski 9 (B.9), M.9 Pajam 2, and M.9 NAKBT337 (M.9 T337) were included as industry standards. The remaining seven rootstocks in the planting were B.62396, CG.3041 [Geneva®41], CG.5935 [Geneva®935], G.16, J-T-EH, Pi Au56-83 and Pi Au51-4. Vertical splitting of the bark on the lower trunk was observed in spring 2009 after a series of freeze-thaw cycles during winter 2008-2009. There were significant rootstock effects on the incidence and severity of visible trunk injury, tree vigor during 2009 and yield in 2008 and 2009. G.16 and B.9 had a lower incidence of visible trunk injury compared to M.26 and M.9 Pajam 2. Visible trunk injury was more severe on M.9 Pajam 2 and M.9 T337 than CG.5935, G.16, and Pi Au 51-4. Surviving tree yields in 2009, expressed as a percentage of yield in the previous year (relative yield), ranged from 18% (Pi Au 56-83) to 92% (G.16). The only rootstocks to yield greater than 50% of the previous year's yield in 2009 were B.62396 (60%), J-T-EH (63%), B.9 (69%), and G.16 (92%). Tree survival was lowest in M.26 (13%) and M.9 Pajam 2 (12%) and highest in G.16 (100%).