Influence of pollen source on fruit production of date palm (Phoenix dactylifera L.) cv. Barhi in humid coastal regions of southern Iran

• Pollen source can improve date production of cv. Barhi in humid coastal regions.
• The highest yielding pollen sources were M07, M08, M09 and M10.
• Pollen source of M05 produced the highest percentages (64%) of khalal.
• M1 and M07 are recommended for late maturity and Jervis No. 1 for early maturity.
• The highest TSS was obtained with pollens from M1, M10, M11 and M12.

Pollen can directly affect fruit development of date palm (Phoenix dactylifera L.) through the process known as ‘metaxenia’. The influence of 12 pollen sources (10 local selections: M1, M2, M05–M09, M10–M12 and 2 internationally recognized cultivars: Fard No. 4 and Jervis No. 1) on fruit set, marketable yield, fruit and seed traits, and time of fruit maturity of cv. Barhi was investigated in the humid coastal region of southern Iran during 2009–2010. The M10 pollen produced the highest fruit set at both kimri (unripe) and rutab (ripe, soft) harvest (71%, 50.5%), while the lowest fruit set was obtained with M05, Fard No. 4 and Jervis No. 1 (<54%, <38.3%). The highest marketable yield of 58.4 kg tree−1, with 24.7% culled fruit, was achieved with M10. Marketable yield and fruit set were correlated (r = 0.688). M07 produced the lowest (19%) and M06 produced the highest (35%) percentage of culled fruit. The proportion of different fruit types at harvest was dependent on the pollen source; khalal (full-size, not ripe) (49.3–64%), rutab (19.8–29.5%), and tamar (ripe, sun-dried) (15.8–27.3%). Jervis No. 1 gave the earliest and M05, M07 and M1 the latest fruit maturity. The highest fruit size and weight (16 g) was obtained with Fard No. 4 and lowest (12.85 g) with M12. Total soluble solids (43.7–47.6%) differed between pollen sources while titrable acidity, reducing and total sugar, moisture content of fruit, and fruit dry matter did not. It is concluded that the pollen source has the potential to modify and improve date production but the responses vary between years and studies. Overall, M10 is the most suitable pollen source for humid coastal region having high fruit set, satisfactory marketable yield and a low percentage of culled fruits.