High temperatures and time to budbreak in low chill apricot ‘Palsteyn’. Towards a better understanding of chill and heat requirements fulfilment |
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| Authors: | José A Campoy David Ruiz Nigel Cook Laura Allderman José Egea |
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| Institution: | 1. Department of Plant Breeding, CEBAS-CSIC, Campus Universitario de Espinardo, Murcia E-30100, P.O. Box 164, Spain;2. Deciduous Fruit Producers Trust Research (fruitgroscience), P.O. Box 12789, Die Boord 7613, Stellenbosch, South Africa;3. ARC Infruitec-Nietvoorbij, Fruit, Wine and Vine Research Institute of the Agricultural Research Council, Private Bag X5013, Stellenbosch 7599, South Africa |
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| Abstract: | The efficiency of different temperature cycles in inducing budburst of one-year-old shoots of the apricot cultivar ‘Palsteyn’ from dormancy was evaluated. Three replications of shoots were collected during two consecutive years from adult trees, following the accumulation of different amounts of chilling in the field. Thereafter, shoots were exposed to different temperature cycles in growth chambers, for 60 days. The temperature treatments included a continuous temperature of 5 °C; daily temperature cycles of 19/5 h at 5/15 °C, at 5/20 °C, and at 5/25 °C; and the same temperature cycles for the remainder of the 60-day period, after pretreatment at 5 °C for 30 or 45 days. After the temperature treatments, shoots were forced at 25 °C until budburst. The mean time to budburst (MTB) (in days) of lateral vegetative, terminal vegetative and reproductive buds was evaluated. The efficiency of the different treatments was greatly influenced by the date on which shoots were cut. High temperatures had a more positive effect on the reduction of MTB when chilling accumulation had occurred in the field instead of the growth chamber. After partial chilling accumulation in the field, high temperatures (25 °C) combined with low temperatures are more efficient than cycles of moderate temperatures (15 or 20 °C) to induce an earlier budburst. In view of these results, a parallel accumulation of both chilling and heat requirements after partial chilling accumulation is suggested. The application of these results could assist in the development of more accurate models for the prediction of the overcoming of dormancy and blooming. |
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| Keywords: | CR chilling requirements CU chill units GDH growing degree hours MTB mean time to budbreak |
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