Assessment of in Vitro Pollen Germination and Pollen Tube Growth of Annona Cherimola Mill

Yield in cherimoya (Annona cherimola Mill.) is affected by various factors reducing fertilization and fruit production such as: the protogynous dichogamy of the flowers, deficient natural pollination, and low pollen quality. The objective of this study was to determine in vitro the differences in pollen quality of nine ecotypes and one cultivar of A. cherimola from pollen samples collected at the female and male phenological stages of flowering. The percentage of pollen germination and the length of pollen tubes was evaluated in vitro at 2 and 24 hours after incubation at 21°C, in two phenological stages of the flowers during bloom in 2018 and 2019 seasons. The germination medium contained: 10% sucrose, 1% agar, 0.005% boric acid, and 0.025% calcium nitrate. Fabulosa and Austro ecotypes and the Fino de Jete cultivar had the highest pollen germination in the male phenological stage, after 2 and 24 hours in both seasons. Fabulosa had the highest percentage of germination in the female stage in both seasons. The ideal phenological stage for pollen collection was at anther dehiscence. Austro and Fabulosa ecotypes had the longest pollen tubes after 2 and 24 hours, in both phenological stages for both seasons. Fabulosa and Austro ecotypes, and Fino de Jete cultivar, showed promising pollen characteristics for hand pollination of cherimoya.