The effect of pollen storage temperatures on pollen viability, fruit set and fruit quality of six date palm cultivars

Asynchronous maturation of male and female flowers in date palm trees is frequently occurs, making pollen storage operation necessary to ensure pollination. The aim of this study was to investigate the effect of pollen storage temperatures on pollen viability, fruit set and fruit quality of six date palm male cultivars. Pollen grains of six date palm cultivars namely 'Bouhlesse', 'Deglat Beida', 'Deglet Nour', 'Ghars', 'Halwaya' and 'Moch Deglat' were stored at room temperature (24 ± 2 °C), 4 °C or −20 °C. In vitro pollen germination and pollen tube growth were examined after 0, 1, 3 and 13 months of storage. Influence of pollen storage on fruit set and fruit quality were also analyzed. Storage temperature, storage duration, cultivar and interaction between all variables had highly significant effect on pollen viability and pollen tube length (p < 0.0001). High values of pollen germination (up to 87%) and pollen tube length were recorded in fresh pollen (at 0 months of storage). For all cultivars, pollen stored at room temperature lost the most of their viability between the 2 or 3 months of storage. However, pollen viability was extended over time when pollen was stored under low temperature, with a storage temperature of −20 °C preferable to 4 °C. Fruit and pulp weight decreased slightly but significantly in most cultivars as a result of pollen storage temperature, although fruit set was not affected. The pollen of 'Deglet Nour' showed high pollen viability after 1 year of storage at −20 °C (∼89%) and may be used as good cultivar for storage.