Abstract
ABSTRACT Temperate climate fruit trees often exhibit uneven budding and flowering, due to the low number of chilling hours that determine the occurrence of dormancy and its depth. The objective of this study was to determine the depth of bud dormancy in peach tree cultivars and evaluate the efficiency of the tetrazolium test for dormancy and comparing with biological test. Branches of the cultivars Aurora 1, Chimarrita, Chiripá, Coral, Eldorado, Granada, Leonense, Maciel, Marli, Premier, and Vanguard were collected between May and August 2008 at two locations: Curitiba and Lapa. The evaluation of dormancy was performed using a biological test of single node cuttings through the parameters: average time for bud burst, velocity of bud burst, final rate of bud burst and rate of vigorous bud burst. For the tetrazolium test, 300 mg of buds was used and the color intensity readings were obtained using a spectrophotometer. The peach tree cultivars evaluated differ in the intensity of dormancy in late fall. The most intense endodormancy cultivars found were: Chiripá, Leonense and Eldorado cultivars, and the weaker cultivars found were: Aurora 1 and Maciel. The tetrazolium test was efficient at estimating the intensity of dormancy in peach trees when the occurrence of cold was suitable for installation endodormancy. At a location with the lowest occurrence of cold (Curitiba), the tetrazolium test did not simulated successfully the biological test results.
Highlights
Dormancy is an important physiological condition in the adaptation of temperate climate fruit trees to environmental conditions
Significant differences were found between peach cultivars for most of the variables analyzed by the biological test and by the tetrazolium test, except for rate of vigorous bud burst (RVB), which exhibited no difference among the cultivars evaluated at the two locations (Table 1)
According to Carvalho and Zanette (2004) a better way to assess the capacity of bud development is to use the variable rate of vigorous bud burst (RVB), which measures the percentage of cuttings with buds that evolved from Green Tip stage to Open Leaves stage
Summary
Dormancy is an important physiological condition in the adaptation of temperate climate fruit trees to environmental conditions. This phenomenon is characterized by the acquisition of cold resistance and growth control (LANG et al, 1987), in which the metabolic activities of the plant continue, at reduced rates (PETRI et al, 2006). Ecodormancy occurs after the overcoming of endodormancy and is characterized by the prevention of bud sprouts due to environmental conditions that limit plant growth, such as the lack of water or temperature extremes (LANG et al, 1987). After the suspension of the limiting factors on the plant, bud sprouting occurs
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