Evaluation of breaking dormancy, flowering and productivity of extra-late and ultra-late flowering almond cultivars during cold and warm seasons in South-East of Spain

Abstract

Abstract Flowering time in almond is a complex process involving chilling and heat requirements. After being exposed to periods of low and high temperatures, the buds are able to break their dormancy state and sprout or flower. For suitable flowering, vegetative growth and fruit set, the chilling requirements have to be fully satisfied. In cold areas, where many new almond orchards are being established, late flowering is an indispensable trait for avoiding damage from late frosts. Due to the expansion of almond cultivation, late-flowering cultivars are also being grown in warm areas, although the long-term behaviour of these cultivars in such climates remains uncertain. In this work, we studied the extra-early flowering almond “Desmayo Largueta”, the extra-late “Penta” and the ultra-late “Tardona” for a period of three years, calculating the chilling requirements of reproductive buds for breaking dormancy, the heat requirements for flowering and the productivity in the warm conditions of South-East of Spain. “Tardona”, bred at our centre, CEBAS-CSIC, is the latest flowering almond cultivar released in the world to date. The chilling requirements (CR) of the cultivars were calculated according to the Richardson and Dynamic models, and the heat requirements (HR) were estimated according to the Richardson model. Results showed important differences in CR and HR between almond cultivars and years. Furthermore, the Dynamic model provided more stable CR estimations than the Richardson model over the years under our experimental conditions especially during warmer seasons. Finally, we observed a decrease in productivity in extra-late- and ultra-late-flowering cultivars in a particularly warm season, when chilling requirements were not fulfilled. This effect demonstrates the importance of growing cultivars in climatically suitable areas and the effect of increase of temperature in flowering and productivity of almond.