Apricot Floral Biology : The Evolution of Dormancy and the Appearance of Bud Anomalies in Several Italian Genotypes

Apricot (Prunus armeniaca L.) is a fruit species showing several problems related to its floral biology with inconstant and extremely low yield attributed to the lack of climatic adaptation when unsatisfactory cropping cannot be traced to strictly genetic factors. This set of phenomena has been attributed to an unsatisfied chilling requirement and an incomplete overcoming of bud dormancy leading to the appearance of flower bud anomalies. The aims of this study were to characterize a large number of native Italian apricot cultivars through evaluation of their floral biology. In particular, chilling requirement, blooming aptitude and susceptibility to the floral anomalies were estimated. The forcing method was used to determine the chilling requirement of 23 Italian germplasm genotypes and classified them into three types: low (< 1000 CU), medium (1000-1200) and high (> 1200). The first two cultivar types have a shorter endodormancy phase, an earlier beginning of flowering and a good blooming entity. However, these cultivars showed high percentages of early anomalous buds. The third group is composed of cultivars that show a low flowering percentage and high levels of later bud drops. Numerous and diversified 'floral anomalies', such as necrosis and pistil abortion, during bud and flower development from endodormancy to bloom, not strictly related to the chilling requirement, were observed.