A System of Defined Phenological Stages for Cold Tolerance and Development of Floricane Inflorescences of Primocane-Fruiting Blackberries

Abstract

Phenological development charts for flower buds are commonly used for many fruit crops and phenology is linked to pest development and cold hardiness. However, no phenological development chart had been developed for blackberry ( Rubusspp.). Observations were made of the floricanes of primocane-fruiting blackberry genotypes, including cultivars ‘Prime-Jan’® and ‘Prime-Jim’®, under high tunnels and ambient conditions in 2008 and 2009. Seven chronologically consistent stages were selected. The usefulness of these stages in predicting resistance to spring freezes and frosts was observed in a spring freeze (-5 °C) in 2008. Buds were selected and phenological stage and the presence or absence of necrosis were recorded. Phenological stage had a significant effect on bud mortality. Bud mortality increased greatly between the stage where the inflorescence was in a tight cluster and the stage where the pedicels had elongated.