Chilling requirement was investigated in six peach [Prunus persica (L.) Batsch] cultivars observing plants in containers, with one or two years, artificially chilled by 150, 300, 450, and 600 hours at 2ºC, and in excised shoots that were periodically taken from the orchard during the rest period. Chilling requirement of 'Precocinho' is 300 hours at 2ºC (around 150 chilling units - CU - using Utah Model) or around 200 hours under 12ºC; 'Riograndense' and 'Eldorado' have 450 chilling hours at 2ºC (225 CU) or 365 chilling hours under 12ºC; 'BR-1' is 450 chilling requirement at 2ºC (225 CU) or 418 chilling hours under 12 ºC; and 'Planalto' and 'Della Nona' are over 600 chilling hours at 2ºC (>300 CU). It was not possible to estimate chilling requirement in 'Della Nona' using temperatures under 12 ºC.
Prunus persica; endodormancy; adaptation
