Association of Reproductive Phenology with Air Temperature in Almond (Prunus dulcis [Mill.] DA Webb) Cultivars Under Northwestern Himalayan Conditions

Knowledge of variability in phenological traits is of utmost importance in breeding new almond cultivars in the context of impending climate change. The Northwestern Himalayan region is characterized by extreme winters, and phenological studies of fruit crops in relation to environmental variables in this region are scant. Flowering time being an important trait governing agricultural productivity, the objectives of this study were the evaluation of local and exotic almond cultivars for blooming initiation and other associated parameters. This study also aimed at deciphering the association between bloom dates in almonds and prevailing temperatures. Field phenological observations were performed during seven growing seasons (2012-2018) in Kashmir. Phenological traits like endodormancy breaking were estimated using the correlation model. The heat requirements for blooming were estimated using the growing degree days (GDD) method. The association between average temperatures and days to flowering was studied using partial least squares (PLS) regression. Local cultivars 'Makhdoom' and 'Shalimar' were earliest to bloom within 80 days, while the exotic cultivars were late bloomers, requiring 87 days. Cultivars 'Makhdoom', 'Shalimar', 'Drake' and 'Pranyaj' broke their endodormancy on the same date, i.e. December 26, although another group including 'Waris', 'California Paper Shell' and 'Merced' exhibited endo- to ecodormancy transition on January 21. In general, Himalayan-origin almond cultivars revealed low heat requirements for flowering compared to the exotic ones. PLS regression analysis identified four major periods in which average temperatures successfully explained variation in days to blooming in almonds. In conclusion, a phenological prediction model is presented here that explains variation in blooming dates in almond cultivars as a function of average temperatures. This model addresses the almond cultivars growing in the Himalayan region and is expected to be of great practical utility to the farming community to efficiently plan their orchard management practices.