Abstract
Thidiazuron [(TDZ)N-phenyl-N′-1,2,3-thidiazol-5-ylurea] at 750 μM was applied to buds of apple trees to determine if it could substitute for the chilling requirement to induce bud break. Shoots of cv. ‘Anna’ (low chill), ‘Delicious’ cv. Redchief (medium chill), and ‘Northern Spy’ (high chill) were untreated, treated with TDZ prior to chilling (before-chill), and treated with TDZ at various intervals after the accumulation of specific amounts of chilling (after-chill). Shoots were stored in a cold room at 4°C. TDZ applied prior to chilling reduced the chill unit (CU) requirement (1 CU = 1 h at 4°C) for the promotion of bud break on 1-year-old shoots of ‘Anna’ and ‘Northern Spy’ and 1- and 2-year-old wood of ‘Delicious.’ TDZ applied after-chill promoted bud break only for ‘Anna’ and buds on 2-year-old wood of ‘Delicious.’ While accumulating CUs, untreated buds or buds treated with TDZ on 1-year ‘Delicious’ and ‘Northern Spy’ did not respond to the cold treatment even after 1848 h of CU accumulation. For all three cultivars, TDZ treatment was more effective in promoting bud break when applied before the initiation of chilling.
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Steffens, G.L., Stutte, G.W. Thidiazuron substitution for chilling requirement in three apple cultivars. J Plant Growth Regul 8, 301–307 (1989). https://doi.org/10.1007/BF02021823
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DOI: https://doi.org/10.1007/BF02021823