Effect of Pollen Treatments on Fruit Yield and Gene Expression in Offshoot and Tissue Culture Date Palms (Phoenix dactylifera L. cv. Barhi)

Abstract

The low performance of date palm cv. Barhi resulting from tissue culturing is one of the main challenges in the production of these plants. On the other hand, the final yield of the plant depends on various metabolic and biochemical factors which are caused by gene expression. The plant reacts to environmental factors to survive in different growth and environmental conditions through gene expression. This experiment was conducted to investigate the relationship between the expression of certain genes before and up to two weeks after pollination with the yield of off-shoot and tissue culture of Phoenix dactylifera L. cv. Barhi (10-year-old). Off-shoot and tissue-culture date palms were pollinated with Red Ghanami pollen, Green Ghanami pollen, and Green Ghanami + Red Ghanami pollen (50:50) based on a factorial design in randomized complete blocks with three replications. To this end, the relative expression levels of Histone acetyltransferase HAC1-like (LOC103717600) (HAC 1), Arginine N-methyltransferase 6.1 (LOC103716582) (ANM), TIME FOR COFFEE-like (LOC103716450) (TFC), Homeobox-leucine zipper protein HOX9-like (LOC103703962) (HOX 9), MADS-box transcription factor 2-like (LOC103702602) (GLO 1), and MADS-box transcription factor 16 (LOC103701267) (DEF 1) genes were examined using qRT-PCR method in 3 times: (1) Before pollination, (2) 1 week after pollination, and (3) 2 weeks after pollination. The fruit yield was measured at 180 days after pollination (the end of the experiment). The results showed that the tissue culture palms had lower yield but higher relative genes expression in all pollen treatments compared to off-shoot palms. Off-shoot date palm pollinated with Red Ghanami pollen (5.93 tons/ha) showed the highest yield while the lowest yield was recorded in tissue culture date palm pollinated with Green Ghanami pollen (2.09 tons/ha). The relative expression of the six studied genes significantly increased in all treatments two weeks after pollination. Two weeks after all investigated treatments, the GLO gene had the highest expression, while the HAC gene showed the lowest relative expression. The relationship between the yield and the genes expression in the three studied times showed that the HOX gene had no considerable effect on flowering and yield. The ANM and TFC genes expression before pollination exhibited a positive relationship, whereas the expression of HAC, DEF, and GLO genes had a negative relationship with 1 week after pollination. Two weeks after pollination, the expression of the ANM gene revealed a significant positive relationship with the final yield of the date palm. Moreover, the correlation results showed the prominent role of the genes in different stages of growth and yield of date palms by influencing the expression of each other. In general, it is possible to improve the yield of the tissue culture date palm by affecting the expression of the genes in specific stages based on their function.