The Influence of Temperature on Pollen Germination and Pollen Tube Growth in Eight Date Palm Cultivars

Failure of pollination in date palms usually happens when temperature drops during the flowering season, causing a reduction in the fruit set and yield. Screening low temperature-tolerant date palm cultivars are needed in order to stabilize yield in such conditions. The present study was conducted to ascertain the impacts of varying temperatures, from 10 to 35 °C at 5 °C intervals, on the pollen germination and tube growth of eight date palm cultivars known as; Bouhlesse 1 (B1), Deglet-Baida 1 (DB1), Deglet-Nour 1 (DN1), Ghars 1 (GH1), Ghars 2 (GH2), Halwaya 1 (HL1), Moch-Deglet 1 (MD1) and Moch-Deglet2 (MD2). The studied cultivars belong to three flowering periods; precocious, medium and late period. Pollen germination and pollen tube growth were influenced by temperature across all cultivars. Nevertheless, the flowering periods did not have any significant impact on pollen germination and pollen tube length. In all cultivars, the optimal temperatures for pollen germination, above 90%, were found between 15 and 30 °C. The optimum temperature, according to the pollen tube growth, was recorded at 20 °C for DN1, H1, MD1 and MD2 and at 25 °C for B1, DB1, G1 and G2, respectively. The lowest rates of pollen germination and pollen tube growth were recorded at 10 °C, with the exception of MD2, G1, and H1, where the pollen germination rate approached 80%. Therefore, these cultivars could be used for pollination of date palm female during cold flowering seasons.