Effects of Preharvest Weather Conditions on Firmness of 'McIntosh' Apples at Harvest Time

Apple fruit firmness is one of the main attributes indicating fruit quality at harvest. It is affected by numerous factors during the entire growing season. The effects of weather conditions during apple development are often mentioned as a result of their impact on attributes linked to fruit firmness: fruit size, calcium concentration, water content, etc. In this study, the effects of weather conditions on 'McIntosh' apple (Malts x domestica Borkh. cv. McIntosh) firmness at harvest time were analyzed. Fruit were harvested at nine sites in Quebec and Ontario over 15 years (1996-2011). For each case, weather parameters were analyzed from full bloom until harvest, either in monthly subperiods from May until September or in terms of days from full bloom (DFB) until harvest. Regression results highlighted the negative effect of lower air temperature conditions from 31 to 60 DFB, higher air temperature conditions and precipitations from 61 to 90 DFB, and higher temperature conditions from 91 DFB until harvest on 'McIntosh' apple firmness level at harvest. Precipitation from 61 to 90 DFB alone explained 39% of 'McIntosh' apple firmness variation at harvest time. The prediction of apple firmness at harvest time could be helpful for producers to adjust their marketing and storage strategies according to apple quality level.