Effects of Pollination Interventions, Plant Age and Source on Hormonal Patterns and Fruit Set of Date Palm (Phoenix dactylifera L.)

Abstract

Date palm is widely propagated through conventional offshoots. It is also produced through a tissue culture technique due to the limited number of offshoots produced throughout the course of a palm’s life. Being dioecious, it is a cross-pollinated tree that can be naturally or artificially pollinated. Tissue-cultured plants often have abnormal epigenetic or genetic changes that affect specific phenotypic characteristics. The growth of parthenocarpic fruits in date palms is mostly induced by hormonal imbalances in certain tissues. The major hormones in parthenocarpic fruits are auxins (IAA), gibberellins (GA3), and abscisic acid (ABA). Parthenocarpic, or abnormal fruit development, is an undesirable trait for date palm growers since it drastically reduces farm income. The current study was therefore conducted over two seasons to confirm previous observations and included conventional offshoot-derived trees (CO) and tissue culture-derived ones (TC) of the cultivar Barhee. According to the observed ratio of the fruiting abnormalities, two date palm tree ages were selected, i.e., 6 and 13 years. Two pollination interventions were used: pollination of naturally open female spathes (NOP) and pollination of forced open female spathes (FOP). Plant hormones, IAA, GA3, and ABA were identified just before pollination and at specific intervals after pollination for up to 85 days. The ratio of the abnormal fruit set was identified 5 days after pollination. Significant differences were observed in hormonal levels between tree ages as well as between tree propagation sources. Young TC trees (6-year-old) had high abnormal fruit sets compared to CO date palm trees that were the same age. During the early fruit growth and development phases, CO date palms had much higher amounts of IAA and GA3 than TC date palms. However, ABA concentrations were surprisingly higher in the TC trees during the early fruit growth stages, while it immediately decreased after pollination in the CO date palms. The ratio of abnormal fruits was significantly reduced in the 13-year-old TC date palms, and no differences were observed compared to the CO ones. The levels of IAA, GA3, and ABA hormones in both young and old date palms derived through CO or TC followed similar patterns. The critical observations regarding the ABA pattern in the old TC date palms (13-year-old) gradually dropped after pollination, which was identical to the CO ones, whereas it was the opposite in the young 6-year-old TC date palm plants.

Study of Changes in the Chemical Composition of Date Palm Fruits (Phoenix dactylifera L.) Derived from Tissue Culture Under the Influence of Different Pollen Treatments

“…And that this difference in the effect of the pollen variety on the rate of falling in the fruits is due to several factors, including compatibility with a certain type of pollen over the other, or the genetic factor that plays a major role in the effect. Or it is a result of increasing levels of plant hormones in female flowers at the second date (after Three days from the blooming of the pollen) [26]. This difference between pollen varieties in affecting the percentage of chives in the fruits may be due to the difference in their content of plant hormones, and this was confirmed by most of the research [27].…”

Applications of AI and IoT for Advancing Date Palm Cultivation in Saudi Arabia

“…Date production and trading help local economies and serve as a source of revenue for farmers and exporters. Over the past few decades, Saudi Arabia's agricultural sector, particularly the date palm sector, has experienced tremendous growth and support [39][40][41][42][43].…”

Effect of period of receptivity and air temperature on parthenocarpic phenomenon of ‘Assiane’ date palm cultivar (Phoenix dactylifera L.)

“…Environmental conditions can have a significant impact on the pollination and fertilization processes. Optimal temperature is essential for different stages of sexual reproduction in flowering plants, such as pollen formation, pollen transfer, the readiness of stigmas for pollen, pollen germination, the growth of pollen tubes, double fertilization, and seed development (Hedhly et al, 2003(Hedhly et al, , 2005Snider and Oosterhuis, 2011;Zulkarnain et al, 2019;Ali-Dinar et al, 2021;Alla et al, 2022). Any form of stress during these stages can result in sterility and, ultimately, reduce crop yields.…”