minimum number hours that resulted in normal bloom was termed the “chilling requirement” for the cultivar. Originally cultivar chilling requirement was determined by forcing twigs at intervals during the winter and noting if 50% budbreak occurred in 3
economic fruit tree; its fruit is consumed as a preserve and a drink in China ( Shi et al., 2009 ). The cultivars of japanese apricot in Taiwan have the lowest chilling requirements in the world ( Ou and Chen, 2003 ). Owing to being greatly restricted by
usually influenced by chilling in winter ( Fuchigami et al., 1982 ; Perry, 1971 ; Wareing, 1956 ). Temperature and duration of chilling are key components of satisfying chilling requirements which are critical to promote vegetative growth and budbreak
chilling requirements are not satisfied adequately, the vegetative and reproductive growth of the cultivar will be affected negatively ( Black, 1952 ; Coville, 1920 ; Ruck, 1975 ; Samish, 1954 ; Weldon, 1934 ). On the contrary, in the case of a cultivar
Chilling requirements of 44 genotypes of Corylus avellana L. were estimated by cutting shoots in the field at weekly intervals and forcing them in a warm greenhouse for four weeks. The chilling requirements of catkins, female flowers, and leaf buds were assumed to have been met when development occurred on more than half of the respective plant parts. Chilling requirements were lowest for catkins and highest for leaf buds, and ranged from <100 to 860 hours for catkins, 290-1550 hours for female flowers, and 365-1395 hours for leaf buds. The lowest chilling requirements were observed for the leading cultivars of Turkey and southern Italy. The yellow-leafed ornamental C. avellana var. aure a had very high chilling requirements for all plant parts.
of growth inhibition of kiwi is apparently in the bud scales because their removal was shown to promote budbreak ( Lionakis and Schwabe, 1984 ). Very little is known concerning the chilling requirement of different kiwi species and cultivars
family are insensitive to photoperiod for dormancy induction ( Heide and Prestrud 2005 ). After a period of chilling, endodormancy is broken and the plant is ready to initiate budbreak. It has been well documented that chilling requirements vary between
deciduous fruit trees in the subtropical environments, including pomegranate, require specific chilling units to break endodormancy before active vegetative growth in the spring. Therefore, planting cultivars with different chilling requirements, in distinct
Abstract
Chilling requirements for 3 pecan cultivars are reported for the first time. Stem cuttings with 4 buds of ‘Desirable’, ‘Mahan’, and ‘Stuart’ pecan (Carya illinoensis (Wang.) K. Koch) were forced in a greenhouse after each 100 hours of field chilling below 7.2°C during the 1969-70, 1970-71 and 1971-72 dormant seasons and bud break measured 21 days later. A chilling requirement of 500 hours was determined for ‘Desirable’ and ‘Mahan’, and 600 hours for Stuart.
The chilling requirements of the University of Arkansas blackberry cultivars Apache, Ouachita, and Prime-Jim*, and the primocane-fruiting selections APF-25, APF-27, APF-40, APF-42, APF-44, APF-46, APF-52, and APF-53 were investigated using stem cuttings from field-grown plants. A biophenometer was used to measure chilling (hours below 7 °C) in the field and 12-node cuttings of lateral shoots were taken from the cultivars every 100 hours up to 1000 hours below 7 °C. However, only 500 chilling hours had occurred at the time of this writing, and the response of budbreak to higher chilling levels could not be reported. The cuttings were placed in a mistchamber in the greenhouse with a daylength of 16 hours and air temperature of 26–29 °C. Percent budbreak was measured weekly. The cultivar × chilling interaction was significant (P = 0.05). `Apache' and `Ouachita' showed little or no budbreak up to 500 h, indicating a higher chilling requirement. The chilling requirement of Prime-Jim was determined to be between 300 h and 400 h, and that of the APF selections appeared to be between 300 h and 500 h. The chilling requirement of APF-53 could not be determined since budbreak was consistent at all levels of chilling up to 500 h. In general, the primocane-fruiting genotypes appeared to require less chilling than floricane-fruiting `Apache' and `Ouachita', and they would therefore be more suitable for low-chill locations.