Influence of weather conditions and rootstock genotypes on flower bud biology and xylem vessel differentiation in apricot

Abstract: The aim of this research was to study the involvement of weather conditions and the influence of two Prunus rootstocks (Myrabolan 29/C and apricot Seedling) on flower bud biology of Pisana (Prunus armeniaca L.), one of the most appreciated Italian apricot cultivar, grown in a Mediterranean agro-climatic environment. Anatomical investigations on xylem differentiation within flower buds and biological observations on flowering as well as fruiting were carried out over two consecutive growth seasons. These years were characterized by different weather conditions due to temperatures and rainfall events which influenced the chilling accumulation, blooming time and xylogenesis process. The onset of xylogenesis within flower buds was conditioned by summer temperatures and water availability. The two rootstocks commonly used in apricot, Myrabolan 29/C and apricot Seedling, did not affect the flowering and fruit-set rate of the grafted cultivar. Nevertheless, differences in progressive differentiation of the secondary thickness of procambial cells in xylem vessels were observed.