Development of a model to estimate the chilling requirement of oriental pear by standardizing dormancy depth

Abstract

The objective of this study was to develop a model to estimate the chilling requirements of 10 oriental pear cultivars by standardizing dormancy depth. The dormancy depth of these cultivars was standardized to a range of 0–100 by setting the lowest bud burst rate during endodormancy as 0 and the bud burst rate immediately after the completion of endodormancy as 100. The endodormancy period was divided into periods. Stage I represented continuously increasing dormancy depth until the deepest dormancy was reached. Stage II represented the period of decreasing dormancy depth following the deepest dormancy; this stage included the breaking of dormancy. In addition, the 10 studied cultivars were classified into three types according to their dormancy depth changing pattern: stage I drop type, stage II leap-up type, and stage I·II symmetric type. A chilling accumulation model was derived based on both the endodormancy period and the dormancy depth of each cultivar. The results showed that − 1.9 to 12.0 °C was an effective range for chilling accumulation and that 2.1–4.0 °C was the most effective range for chilling accumulation. The results also revealed that negative accumulation, the reverse reaction of chilling accumulation, occurred under high-temperature conditions (above 14 °C). The results of the model verification process confirmed that the high-temperature conditions (above 14 °C) exhibited negative accumulation values due to an inverse relationship with dormancy depth during endodormancy stage I and that the chilling accumulation for the actual dormancy break mostly occurred during endodormancy stage II. © 2019, Korean Society for Horticultural Science.