S16 - Session P3 - The effect of plant growth regulators on the establishment of tissue culture and offshoot date palm (Phoenix dactylifera)

Authors: Peggy Mauk *, Rui Li, Anthony Fortier, Carol Lovatt

Date palm (Phoenix dactylifera) is an important crop in arid/semi-arid regions of the world. Traditionally, date palms are propagated by vegetative offshoots. However, offshoot transplanting success is frequently low (30-50% mortality), resulting in economic loss. Tissue culture (TC) is used for propagation where Fusarium wilt is prevalent. TC-palms are becoming more widely accepted in the U.S. and Mexico; however, growers are concerned that TC-palms are delayed in bearing fruit compared to offshoots. We investigated the efficacy of foliar- and soil-applied plant growth regulators (PGRs) to increase the growth and maturity of TC-palms (Phoenix Agritech) and offshoots in a new orchard at University of California, Riverside, Coachella Valley Agricultural Research Station. Our results showed TC-palms treated with foliar-applied Gibberellic Acid (GA 3 , 25 mg/L) had longer leaves for 1 year. Number of offshoots/mother plant was greater with foliar GA 3 or foliar 6-benzyladenine (6-BA, 25 mg/L) after 16-mo of treatment, with the effect persisting for over 2 years. TC-palms treated with foliar 6-BA and foliar GA 3 had a significantly larger basal circumference after 23 months of treatment, sustained for over 1 year. At year 4, 60% of the TC-palms treated with soil-applied adenosine (ADO, 100 mg/L) produced significantly more fruit compared to only 20% of the untreated TC-palms and 0% of all other treatments. In comparison to offshoots, TC-palm fruit were comparable in quality, morphology, and texture. Offshoots produced at 3-yr and TC-palm at 4-yr. There were no significant differences between treatments for fruit production. Offshoot survival was increased to 100% with soil-applied ADO and coconut water; soil-applied 6-BA had the lowest survival at 40%. Over 3 years, offshoots treated with soil-ADO or foliar-ADO had a 116% increase in fruit weight. Our results indicate PGRs have the potential to increase the maturity and yields for TC-palms and improve transplant survival for offshoots.