Growth and fruiting of 'Elstar' apple trees in response to prohexadione calcium depending on the rootstock
2004
Basak, A.
Trials were conducted on mature apple trees cv. Elstar grafted on two rootstocks: M26 of moderate vigour and M9 – dwarf. Both groups of trees were treated with prohexadione-Ca (ProCa) in two vegetative seasons: 1998 and 2000. The same program of ProCa use was tested in each experiment. The bioregulator was used in concentrations: 125, 175, 200, and 125 + 75 mg/L. The first spray application was performed soon after bloom, on terminal shoots 5-10 cm long, the second treatment three weeks later. The following observations and measurements were gathered: dynamics of shoot growth, the number and length of all shoots per tree, the tendency to regrowth at the end of summer, the number of spurs, fruit set, yield, fruit size, the effect on red colour, shape of fruits and their “internal” quality (firmness, °Brix), as well as the subsequent effect of ProCa use on bloom intensity and growth of terminal shoots the following year. It was found that there were some significant differences in the response of ‘Elstar’ trees to spraying with ProCa between the trees grafted on M26 rootstock and those on M9. The results of the trials showed that trees on dwarf rootstocks require lower doses of ProCa than those grafted on more vigorous rootstocks. In cases of over dosage some negative effects of ProCa were observed.
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