Relationships among the rootstock and morphogenetic behaviour of apple tree in aspect for fruit quality

The relationships among rootstock and some physiological (yield, fruit quality) and physical (endogenous hormones, leaf mineral composition) indices and their effect on fruit quality were evaluated. The commercial important apple cultivar ‘Ligol’ was grafted on semi-dwarf rootstock M.26, dwarf rootstock M.9, and super-dwarf rootstock P 22. Crop load was adjusted to 60, 105 and 150 inflorescences tree^‑1. Crop load and the rootstock influenced apple yield, fruit weight, most of fruit quality and maturity parameters as well as nutrient status of ‘Ligol’ apple tree. Higher crop load guaranteed higher yields, but smaller fruits. Better fruit colour and faster maturation was achieved at low crop load. P 22 rootstock had negative effect on fruit weight, but the apples on this rootstock were more firm and ripen faster. The concentration of tested hormones and total leaf nutrients were significantly higher in apple trees grafted on M.9 rootstock, but mineral status did not depend on the crop load. Generally, reduced apple tree vigor resulted in significant increase of N, K, and Fe. Observed hormonal changes showed that IAA and ABA can be control factors of ripening as sharp increase of both hormones accumulation occurred and followed with relevant fruit quality indices – significant increase of IAA concentration in trees grafted on M.9 rootstock lead to slower ripening; significant increase of ABA concentration and the fastest ripening was found in ‘Ligol’ apple trees with the lowest crop load.