ISHS Acta Horticulturae 367: VI International Symposium on Pear Growing
DORMANCY OF ‘PACKHAM'S TRIUMPH’ AND ‘WINTER NELIS’ PEAR BUDS IN RELATION WITH WINTER CHILLING, HYDROGEN CYANAMIDE AND THIOUREA. |
| Authors: | G. F. Gil, M. Lyon |
| Keywords: | Pyrus communis, budbreak, chemicals, rest |
| Abstract:
The control of dormancy and bud break is important for growing pears under low chilling conditions and also to advance bloom time of the cv. ‘Winter Nelis’ used to pollenize the earlier flowering cv. ‘Packham's Triumph’ in Chile. Cuttings were obtained at different times from trees subjected to winter climate in the field and forced to grow at 20°C in a chamber with or without bud treatment with hydrogen cyanamide or thiourea at 1% or 2%. ‘Winter Nelis’ showed lower field chilling requirement (i.e. 795 hrs. vs. 868 hrs. for 90% bud break), specially for low percentages of bud break, and lower heat requirement for bud break after longer cold exposure. Hydrogen cyanamide at 1% or 2% induced 50% of potential bud break in ‘Packham's Triumph’ previously exposed to 78% and in ‘Winter Nelis’ to 30–60% of their chilling requirements but the process took twice as long than normal. Hydrogen cyanamide at 2% was inhibitory after more than necessary chilling. Thiourea at 2% was less effective and at 1% was ineffective. Bud break of ‘Winter Nelis’ can be regulated and timed by treatment with hydrogen cyanamide according with the amount of chilling received by buds while that of ‘Packham's Triumph’ can be advanced but with less flexibility. Cuttings receiving chilling in coldroom had lower percentages of bud break but behaved as those chilled in the field in response to cyanamide or thiourea. | |
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