Effect of the Accumulated Effective Chilling Hours at the Pruning Time on Budbreak Table Grape on Dessertic Condition

Abstract

The grape crop is important in Sonora State, Mexico, even though the grape growers have some problems that put in risk its continuity. To decide the moment of pruning time is one of the important decisions that the grower must done, because that depends partly the moment and the magnitude the budbreak appeared. The objective of this study was to determine the pruning time using the Effective Chilling Hours (ECH) obtained from the climatologic station. In a commercial lot of the Superior Seedless variety, we studied the effects of pruning at different times depending on the accumulation of ECH (150, 200, 250, 350, and 400). The ECH was calculated by adding the hours that the temperature stayed in following rank 0 °C < X < 10 °C, reducing the hours when the temperature was greater or equal to 25 °C. The data used to calculate this were obtained from the two climatologic stations near the lot in study. The effect in the budbreak was studied in canes and spurs. The results obtained in this study show that the final budbreak in canes as in spurs were not affected by the treatments in study and it was 76.5% and 81.8% for canes and spurs respectively. There is a direct relation (R2 = 0.94) between the ECH at pruning time and the percentage of early budbreak in the canes—from 5.6% (150 ECH) to 54.1% (400 ECH). Whereas in spurs, the early budbreak was favored when pruning is done after at least 200 ECH.