Climatic seasonality influences the development of pollen grains and fruiting in Annona squamosa

Abstract

Artificial pollination is key in the commercial production of the sugar apple (Annona squamosa). The influence of the marked climatic seasonality typical of the semi-arid regions, characterized by two seasons (dry and rainy) where this crop is grown on pollen grain development and performance and, consequently, productivity is unclear. To assess whether pre- and post-pollination events are sensitive to seasonal variations, the anther structure, the pollen grain ultrastructure and germination, the in vitro growth of the pollen tube and the fruit set of the species were investigated in the dry and rainy seasons in central Brazil. Floral bud development time and thermal requirement were, 22 days and 360.8 degree-days in the dry season and 34 days and 622.2 degree-days in the rainy season, respectively. Anther development was slower in the rainy season, but the anatomy was not affected. Pollen grains showed greater mucilage content, reserve accumulation, in vitro germination and pollen tube length in the rainy season. Although seasonality did not influence the efficiency of artificial pollination, its effects on microsporogenesis and microgametogenesis, promote higher fruit quality in the rainy season.