BUD DORMANCY INTENSITY IN PEACH TREE CULTIVARS BY BIOLOGICAL AND TETRAZOLIUM TEST

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, Chiripa, 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: Chiripa, 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.