Return Bloom on 'Golden Delicious' Apple Trees as Affected by Previous Season's Crop Density on Three Rootstocks at 11 Locations

Abstract

'Golden Delicious' apple trees [ Malusx domestica(Borkh.) Mansf] on three dwarfing rootstocks (M.9 NA-KBT337, G.16 and M.26 EMLA) were grown at 11 locations and crop densities were adjusted to various crop densities, ranging from 3.0 to 14.0 fruit/cm ²of trunk cross-section area, to determine if rootstock influenced the relationship between crop density and return bloom. Depending on the location, data were available for one to six years. In total there were 36 location-year combinations. Analysis of covariance was used to evaluate the separate and the interactive effects of previous season's crop density and rootstock on flower density expressed as flowers/cm ²branch cross-sectional area. Flower density was negatively related to the previous season's crop density in a linear manner 43% of the time and rootstock significantly affected flower density 32% of the time. Since there was never an interaction between rootstock and previous season's crop density, the two factors affected flower density independently. Rootstock sometimes influenced flower density in seasons following both low and high crop densities, but the level of flower density was not consistently associated with any rootstock.