Effect Of plant growth regulators on De-greening & Cold storage of Tango And Sugar Belle citrus Varieties Daniel Adu Boakye dadu.boakye@ufl.edu

Introduction Tango and sugar belle growers prefer uniform color break or maturation to ensure harvesting of fruits within specific periods with good internal qualities. Gibberellic Acid (GA3) Brassinosteroid (HBr) Abscisic Acid (ABA) These plant growth regulators influence color maturation but no report has been made on their effects on tango and sugar belle. GA3 retards fruit senescence while brassinosteriods increase fruit peel coloration. ABA hastens ripening and chlorophyll breakdown, thus advancing peel coloration or maturation. Influence color break or maturation in citrus.

Objective To assess the effect of plant growth regulators on de-greening and cold storage conditions of Tango and Sugar belle citrus varieties To evaluate the effect of plant growth regulators on internal qualities after de-greening and cold storage Daniel Adu Boakye - dadu.boakye@ufl.edu

Materials and Methods Varieties: Sugar belle and Tango Treatments Used Abscisic acid (ABA), 1 mM Gibberellic Acid (GA3), 20 ppm. Brassinosteriods (HBr), 1 uM Control (water) Samples for cold storage and de-greening were collected from two groves. That is, sugar belle from UF - SWFREC Demonstration groves, Immokalee and tango from Martin’s grove, Labelle Daniel Adu Boakye - dadu.boakye@ufl.edu

Materials and Methods Treatments Application Data Collected Data Analysis Harvested fruits for Cold storage & De-greening Internal qualities Brix Titratable acidity Treatments were applied after harvesting of fruits Color advancement Chroma meter Data Collection Interval Cold storage – 6 days interval De-greened fruits – 2 days (48 hours) Chroma meter was used to measure peel color at initial stage and periodically for fruits that were de-greened and cold room storage. Brix-acid ratio was determined by dividing brix by titratable acidity. Where levels of brix or solid soluble content was determined using refractometer and % titratable acidity (% acid) was evaluated using garner et al., method and with the formula above refractometer 84 o F and 95 % RH with 5 ppm of ethylene (de-greening) 84 o F and 95 % RH with no ethylene (de-greening control) Cold storage at 45 F (7.2 C)

Results The plant growth regulators had slight effect (or no effect) on the peel coloration or maturation by Day 12 particularly as water (control) influenced the peel coloration more than all the PGR. But the mild peel color advancement from Day 0 to Day 6 can be link to loss of the sensible heat due to the cold storage Daniel Adu Boakye - dadu.boakye@ufl.edu

Results In cold storage, the plant growth regulators did not have significant effect on peel color advancement or coloration particularly when compared with water (control). Though there were slight changes in coloration on Brassinosteroid (HBr) and Abscisic acid (ABA) which may be as a results of shedding off the sensible heat. Tango’s response to the PGRs is very low according to this study.

Some photos Sugar belle Tango Control (water) Control (water) Abscisic acid Abscisic acid Comparatively, the control is not different from Abscisic acid (as well as the other growth regulators) especially on day 12. This confirms that these plant growth regulators were not able to advance peel color maturation of sugar belle and tango in cold storage 4c 4d 4c 4d Figures 3-4: Effect of Plant growth regulators on sugar belle and tango fruits before (3a, 3c, 4a & 4c) cold storage and after 12 days (3b, 3d, 4b & 4d) of cold storage Daniel Adu Boakye - dadu.boakye@ufl.edu

Results Peel coloration of tango fruits were not significantly influenced by temperature at 84 F and relative humidity at 95 %. Higher temperature and relative humidity are known to advance maturation in climacteric fruits but they have slight effect on non-climacteric fruits or products since ethylene production is minimal

Results Brassinosteroid (HBr) and GA3 did not make any significant contribution in the peel color advancement when compared with control but comparatively abscisic acid was significant than all the other treatments after 48 hours of de-greening. But when this figure 5a is compared with figure 5b, it can be revealed that addition of ethylene had significant influence in peel coloration or advancement of the fruits, thus when the initial or before de-greening is compared with 48 hours after de-greening

Results The temperature and relative humidity advanced peel coloration but it cannot be fully associated to the plant growth regulators since the control (water) changed or advanced in color more than all the PGRs. Also abscisic acid (ABA) and Brassinosteroid were expected to advance in color more than GA (20 ppm) since ABA is known to advance peel color development and GA (20 ppm) delay senescence or peel coloration.

Results Comparatively, the effect of Plant growth regulators on color break or maturation of sugar belle is mild. The color maturation of the control (water) is similar to all the plant growth regulators especially after 48 hours of de-greening. Effect of de-greening is significant in advancing peel coloration when figure 6a and 6b are compared. Thus, sugar belle advanced in coloration with de-greening than tango which means that sugar response to 5 ppm ethylene, 84 F and 95 % RH treatment more than tango

Some Photos on Sugar belle & Tango Before and after De-greening The figure 7 (a & b) is the control for sugar belle while figure 8 (a & b) is the Brassinosteroid (HBr) for tango Figures 7 & 8: Sugar belle fruits before (1A) de-greening and after (1B) de-greening; 2A- before de-greening of tango and after de-greening Daniel Adu Boakye - dadu.boakye@ufl.edu

Brix-acid ratio of Tango and Sugar belle Results Figure 9a: Sugar belle Initial water HBr (1 µM) GA (20 ppm) ABA (1mM) Cold storage 6.6 10.1 6.2 7.8 6.3 De-greening 5.8 9.4 7.6 9.3 Figure 9b: Tango Initial water HBr (1 µM) GA (20 ppm) ABA (1mM) Cold storage 12.8 10.1 9.8 10 8.7 84 F & 95 % (no ethylene) 11.4 14.5 12 18.3 14.2 Increase in temperature, increased brix-acid ratio either with ethylene or without ethylene when compared with cold storage of all the two varieties irrespective of the plant growth regulator except sugar belle’s control and GA (20 ppm). Brix-acid ratio is very essential since it constitutes a measure of the balance between sugars and acids. It serves as indicator of the palatability of the juice where larger values indicate sweeter taste. (Note: Brix-acid ratio= Brix/Titratable acidity). At an increased temperature irrespective of relative humidity result to increase in brix-acid ratio in the fruits as a result of decrease in titratable acidity or citric acid (Burdon et al., 2006).

De-greening enhanced coloration in sugar belle than in tango. The mild effects of ABA and HBr suggest that plant growth regulators interaction with de- greening might have been impaired There was increase brix-acid ratio either with ethylene (de-greened) or without ethylene when compared with cold storage of all the two varieties except sugar belle’s control and GA (20 ppm) Conclusion