Effects Of Different Crop Loads On Physiological, Yield And Fruit Quality Of 'Joya (Tm)' Apple Trees: High Crop Load Decreases Maximum Daily Trunk Diameter And Does Not Affect Stem Water Potential

This study aimed to evaluate the effects of different crop load levels on apple trees' yield and physiological characteristics, emphasizing the relationship between stem water potential and crop load and the link between trunk diameter growth and crop load. It was conducted in 2014 at Station Experimentale Fruits et Legumes (SUDEXPE-CEHM) in Southern France. The 'Joya (TM)' apple on Pajam-1 rootstock was used as the plant material. Trees were subjected to hand thinning to obtain four final crop load levels as high (100%; 10 fruit/cm(2) of branch cross-sectional area (BCSA)), medium-high (75%; 7.5 fruit/cm(2) of BCSA), medium-low (50%; 5 fruit/cm(2) of BCSA) and low (25%; 2.5 fruit/cm(2) of BCSA). The four crop load levels were set up in a randomized block design with four replications, and each plot was formed of five uniform trees. Stem water potential was weakly affected by crop load but was mainly driven by vapor pressure deficit. The maximum daily trunk diameter, by and large, reduced while crop load level increased. The increase in crop load level was negatively related to fruit size, acidity and soluble solids content. Crop load did not affect bitter pit incidence. However, in parallel to the increasing crop load level, cumulative yield, yield efficiency and water productivity increased.