IMPACT OF SEASONAL CLIMATE VARIABILITY ON THE PHENOLOGY OF PEAR (Pyrus communis L.) CV. WILLIAMS FROM RÍO NEGROARGENTINA

Abstract

Interannual variability in timing of bloom in pear (Pyrus communis L.) affects crop yield. Air temperature is the main regulator of the phenological development of deciduous fruit trees and causes the interannual variability of flowering date for the pear tree. Bloom occurring 10 days earlier
or later than normal has a high impact on fruit quality and yield. The objective of this work was to evaluate bioclimatic indices that allow predicting the flowering time of pear trees. Temperature records of the 1971-2016 series were analyzed, using daily maximum and minimum values and the
full flowering dates of the same period. The assessed indexes allowed for a proper estimation of full flowering date of pear tree cv. Williams. The greatest probability of occurrence of full bloom, earlier 10 days than average, occurs with an optimal accumulation of chilling hours and an accumulation of
heat units that reaches 70% of the total requirement before September 11. On the contrary, the highest probability of occurrence of blooms with a delay greater than 10 days with respect to the average, occurs with a deficit of chilling hours and a deficit in the accumulation of heat units, covering 50%
of the total heat requirement after September 11. The bioclimatic indices used are efficiently adapted to the temperature conditions of the study area and satisfactorily represent the ecophysiological response of pear.