Chilling accumulation, dormancy release temperature, and the role of leaves in olive reproductive budburst: Evaluation using shoot explants

Effects of various winter chilling regimes on flowering quality indicatorsof Greek olive cultivars

“…Growing olive plants constantly over 16 °C in a greenhouse results in a complete absence of inflorescence in other cultivars (Hackett and Hartman 1967). A reduced number of flowers per inflorescence and a reduced percentage of perfect flowers due to chilling deficit observed in the present work are in agreement with previous studies in other olive cultivars, e.g., absence or asynchronous flowering in new olive growing areas (Castillo-Llanque et al 2014, Aybar et al 2015 as well as a reduced number of inflorescence and an increased ovary abortion (Deng et al 1988) may be related to chilling accumulation deficit of the grown cultivars as reported in Ramos et al (2018). However, during springtime, when CR fulfillment has been completed and inflorescence approach anthesis, low-temperature incidents may have negative impacts on flowering and fruit set of olive (Koubouris et al 2010a).…”

“…There seems to be differentiation among treatments achieved by our experimental design. Also, the temperature fluctuation inside the greenhouse followed the trend of ambient conditions observed outdoors providing a more realistic environment for chilling accumulation studies compared to studies at growth chambers where the temperature is set to be almost stable throughout the day (Ramos et al 2018). When even a higher accuracy in environmental conditions is desired, the suggested strategy is to employ open-top chambers with artificial temperature control as successfully tested by Benlloch-Gonzalez et al (2018).…”

“…When even a higher accuracy in environmental conditions is desired, the suggested strategy is to employ open-top chambers with artificial temperature control as successfully tested by Benlloch-Gonzalez et al (2018). Another available method for chilling accumulation studies would be sampling explants and forcing them in growth chambers under the desired temperature regimes (Ramos et al 2018). In any case, it should be noted that variation of day/night temperatures plays a role in chilling accumulation efficiency since maintaining plants in a constant temperature of 7 °C results in minimal flowering (Denney and McEachern 1983).…”

“…Plants often employ a physiological mechanism called dormancy (expressed as vegetative growth arrest and often leaf dehiscence) to survive during the cold winter period and avoid frost damage (Ramos et al 2018). However, low winter temperatures (e.g., above 1.5 °C and below 16 -19 °C), may have beneficial effects on plant biological cycle (Cesaraccio et al 2004).…”

“…Similarly, some olive cultivars, such as Sevillano and Ascolana are considered to have a very high CR (Kailis and Harris 2007), whereas in North African countries, local olive cultivars grow and produce sufficient yields under hot environmental conditions (Acila et al 2017). There is also a debate on the efficiency of different temperatures for chilling accumulation and break of dormancy, e.g., 7 ο C was initially considered as optimal (Hartman and Porlingis 1957), but a higher temperature of 12.5 ο C was suggested more recently (Ramos et al 2018).…”