Pollen production and flower anomalies in apricot (Prunus armeniaca L.) cultivars

Abnormally developed pistils often occur in different apricot cultivars, as a consequence of physiological-biochemical factors and climatic conditions. Apricot is genetically prone to the formation of a high percentage of flowers morphologically hermaphroditic but physiologically unisexual due to pistil hypotrophy, atrophy and/or necrosis. The number of anthers, the amount of the total and stainable number of pollen grains per anther and per flower and flower (pistil) anomalies have been investigated in apricot (Prunus armeniaca L.) cultivars. Anthers and pollen were investigated for two years, 2004 and 2005, whereas flower bud differentiation and anomalies for three years, 2008, 2009 and 2010.Pistil hypo(a)-trophy anomalies occurred between the Baggiolini stages C and D and appeared to be significantly more frequent on the basal portion of long twigs with respect to either the apical portion or spurs and short twigs. All pollen characteristics taken into account varied significantly among the cultivars. The number of anthers per flower ranged from a maximum of 33.2 ('Rouge de Fournes') to a minimum of 22.6 ('Boccuccia Liscia'); the number of pollen grains per anther ranged from 2369 ('Kioto') to 1267 ('Ninfa'), and the pollen stainability was very high in all the examined cultivars (95.0-98.8%). The mean number of stainable pollen grains per flower was 57,149, ranging from 35,629 ('Boccuccia Liscia') up to 76,728 ('San Castrese'). These results indicate that cultivars both producing the greatest amount of stainable and compatible pollen grains per flower and bearing mainly on spurs or short twigs (lower flower anomalies) should be preferred either when planting new apricot orchards or for breeding programs.