Optimizing Storage and In vitro Germination of Date Palm (Phoenix dactylifera) Pollen

Iran is one of the main date (Phoenix dactylifera) producing countries in the world. however, little information is available on the pollen viability and favorable storage conditions of Iranian male date cultivars. This study was conducted to estimate the best in vitro pollen germination of three male date palm cultivars, 'Ghanami', 'Samsmavi' and 'Gheibani' using various doses of boric acid (0, 50, 100 and 200 mg L-1), calcium nitrate (0, 200 and 300 mg L-1) and sucrose (15% and 25% (w/v)) in a Modified Brebaker and Kwack (MBK) medium. The results showed that the best germination was achieved with 50 mg L-1 boric acid, 200 mg L-1 calcium nitrate and 15% (w/v) sucrose. Once the optimal in vitro germination medium had been established, pollen viability (% germination) of these three cultivars stored for up to 200 days at room temperature (dark and light), in a refrigerator (4 degrees C), freezer (-20 degrees C) and in liquid nitrogen (-196 degrees C) was compared. For all the tested cultivars, germination declined as storage temperature increased and, by 200 days, the highest survival rate was obtained with cryostored pollen. Long-term storage of date pollen using an ultra-low temperature (-196 degrees C) can be used without any deteriorating effect on pollen viability, while room temperature storage significantly reduced pollen germination.