Blossom dates for 41 peaches and nectarines accesses from the Active Gene Bank (BAG) of stone fruits were evaluated at Capão Bonito (SP), Brazil. Observations of flowering date (70% of opened flowers) were taken and compared to the chilling hour's requirement (NHF) considering 7.2 and 13ºC. The NHF was estimated using multiple regression equations based on maximum and minimum temperature. The accesses from the BAG were separated by cluster analysis into four groups for peaches and three for nectarines by cluster analysis. The following peaches accesses: IAC 2485-6, IAC 680-13 and Régis and for nectarine: IAC N 785- 9 showed flowering date before July 10th with NHF less than 40 and 500, below 7.2 and 13ºC, respectively. The peach cultivars Eldorado, Diamante, Arlequim, Bolão, and Marli showed blossom dates after August 1st, requiring more than 70 and 650 NHF bellow 7.2 and 13ºC, respectively. The main peach cultivars for São Paulo State like: Aurora-1, Douradão and Dourado-1, flowered from July 11 to 20 with NHF from 41 to 50 bellow 7.2ºC and from 501 to 560 bellow 13ºC.
Prunus persica; endodormancy; stone fruit
