2019 ASHS Annual Conference

We evaluated the effect of several plant growth regulators on cold storage and degreening of the mandarin ‘Tango’ (Citrus reticulata Blanco) and the mandarin hybrid ‘SugarBelle’[‘Clementine’ mandarin (Citrus reticulata) x ‘Minneola’ tangelo (Citrus x Tangelo), ‘Duncan’ grapefruit (Citrus paradisi) x ‘Dancy’ tangerine (Citrus reticulata)] citrus varieties to assess their impact on peel coloration and internal quality after harvest. Fruit from both varieties were harvested at the color break stage and subjected to cold storage at 45 F (7.2 ºC), hormonal treatments and de-greening. Plant growth regulator (PGR) treatments were abscisic acid (ABA) 1 mM, gibberellic acid (GA3) 20 ppm, homobrassinolide (HBr) 1 µM, and water (control). Three replicates of 10 fruit per variety were used for each treatment and condition. Peel color was measured in PGR-treated cold-stored fruit at six days interval (day 0, 6 and 12). After 12 days, a subset of fruits from each PGR treatment was subjected to de-greening (84 o F and 95 % RH) with 5 ppm of ethylene or without ethylene (air). Peel maturation was measured every two days (day 0, end of 48 hrs of de-greening and 48 hrs after de-greening). We also measured total soluble solid content and titratable acidity to determine the SSC/TTA ratio. During cold storage, any of the PGRs assayed did not have significant effect on peel color advancement particularly when compared with water (control) for both varieties. Storage at 84 o F and 95 % RH in air advanced peel coloration in ‘Sugarbelle’ more than in ‘Tango’. De-greening with ethylene significantly advanced peel coloration on ABA-treated fruits of ‘Tango’ as compared to the rest of PGRs after 48 hours of degreening, whereas in ‘Sugarbelle’ ethylene had similar effect on all PGR treatments. The SSC/TTA ratio was increased after storage at 84 o F and 95 % RH irrespective of ethylene or air treatment in both varieties as compared to cold storage except water and GA-treated fruit from ‘SugarBelle’.