Articles
INFLUENCE OF CHILLING ACCUMULATION TIME ON “FLOWER BUD ABORTION” OCCURRENCE IN JAPANESE PEAR GROWN UNDER MILD WINTER CONDITIONS
Article number
872_6
Pages
69 – 76
Language
English
Abstract
Mild and high temperature fluctuation during the autumn-winter season in Southern Brazil triggered a phenomenon called flower bud abortion, which reduces the number of flowers and result in low Japanese pear production.
The main objective of this work was to study the effects of insufficient chilling at different times of dormancy in Japanese pear potted plants and their relation to the flower bud abortion phenomenon.
For this purpose, two Housui and Kousui cultivars, which had different performance under insufficient chilling accumulation, were used.
For the determination of the dormancy overcoming, two classic models were used: amount of chilling hours (CH) below 7.2°C during endodormancy phase and the growth degree hours (GDH) during heating accumulation on ecodormancy phase; another model, called developmental stage index (DVI), was used for both phases of dormancy.
The flower bud abortion was observed in all treatments, and its incidence was higher in Housui than in Kousui. With delaying chilling treatment, the occurrence of the phenomenon increased.
Compared to the first year of experiment (2005-06), the second year (2006-07) had higher average temperatures during period of chilling accumulation in all treatments, and this was reflected on DVI progression and duration in both stages of dormancy: the time necessary to accumulate 600CH and GDH necessary for flowering increased in all treatments during the second year of the experiment.
These results suggested that the temperature range at the initial phase of dormancy affects on flower bud abortion occurrence, chilling requirement and duration of dormancy more in Housui than in Kousui.
The main objective of this work was to study the effects of insufficient chilling at different times of dormancy in Japanese pear potted plants and their relation to the flower bud abortion phenomenon.
For this purpose, two Housui and Kousui cultivars, which had different performance under insufficient chilling accumulation, were used.
For the determination of the dormancy overcoming, two classic models were used: amount of chilling hours (CH) below 7.2°C during endodormancy phase and the growth degree hours (GDH) during heating accumulation on ecodormancy phase; another model, called developmental stage index (DVI), was used for both phases of dormancy.
The flower bud abortion was observed in all treatments, and its incidence was higher in Housui than in Kousui. With delaying chilling treatment, the occurrence of the phenomenon increased.
Compared to the first year of experiment (2005-06), the second year (2006-07) had higher average temperatures during period of chilling accumulation in all treatments, and this was reflected on DVI progression and duration in both stages of dormancy: the time necessary to accumulate 600CH and GDH necessary for flowering increased in all treatments during the second year of the experiment.
These results suggested that the temperature range at the initial phase of dormancy affects on flower bud abortion occurrence, chilling requirement and duration of dormancy more in Housui than in Kousui.
Authors
R.R. Yamamoto, Y. Sekozawa, S. Sugaya, H. Gemma
Keywords
budbreak, chilling requirements, dormancy, DVI model, primordia necrosis, Pyrus pyrifolia
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