Relationships between apple tree rootstock, crop-load, plant nutritional status and yield

- Yield, fruit weight were crop-load, while metabolite changes were rootstock dependent.
- Mineral sufficiency was dependent on both rootstock and crop-load.
- Super-dwarfing P 22 rootstock resulted in the smallest yield and fruits.

Impact of the choice of rootstock and crop-load on apple tree nutritional status and yield relationships between biochemical parameters were analysed. Apple cultivar 'Ligol' was grafted onto semi-dwarfing rootstock M.26; dwarfing rootstocks M.9, P 67 and B.396; and super-dwarfing rootstock P 22. Crop-load was adjusted to 60, 105 or 150 inflorescences per tree. Flower buds were removed at the pink bud stage. Super-dwarfing P 22 rootstock under intensive crop-load (150 inflorescences per tree) resulted in N deficiency in the leaves, which caused an accumulation of leaf sugars. Leaf elements were influenced by rootstock and crop-load. With the dwarfing rootstocks P 67 and B.396, a significantly larger leaf area and a decrease in photosynthetic pigment and leaf carbohydrate content were observed. Apple tree yield was directly correlated with the crop- load and the number of fruits, independent of the rootstock onto which they were grafted. Average fruit weight, independent of rootstock, was inversely related to crop- load. Generally, yield, fruit weight were crop-load, while metabolite changes were rootstock dependent. Mineral sufficiency was dependent on rootstock and crop-load. Super-dwarfing P 22 rootstock resulted in the smallest yield and fruits.