STUDIES ON APPLE FRUIT ABSCISSION AND GROWTH AS AFFECTED BY CYTOKININS

Thinning trials were conducted for two years (1998-1999) on trees of Gala-derived cultivars (‘Mondial Gala’ and ‘Galaxy’), using NAA and CPPU. In both cultivars CPPU, alone or in combination with NAA, has proven rather successful, always increasing fruit size.
In both years and for both active ingredients the most effective concentration was 10 ppm, at various stages of fruit ontogeny.
These applications resulted in reduced crop density (fruit number per trunk cross sectional area, TCSA) and always increased fruit size compared to hand-thinned controls.
CPPU was also tested as a promoter of fruit growth, applied after trees had been thinned to optimum fruit load.
Twenty ppm a.i., applied when the king fruit reached 20 mm diameter, increased fruit size, improving yield per tree.
Earlier modelling work on fruit growth has led to the hypothesis whether CPPU’s mode of action might be via a cell division stimulation, resulting in greater numbers of cells in the cortical parenchyma of the treated fruits.
To test this hypothesis, cell counts were taken on fruit from the 1999 trial.

VII International Symposium on Orchard and Plantation Systems

G. Costa, L. Corelli-Grappadelli, F. Bucchi

Apple, fruit growth, modelling, chemical thinning, fruit quality, stereology

https://doi.org/10.17660/ActaHortic.2001.557.31