Effects of Exogenous Abscisic Acid On Carotenoids and Fruit Quality in 'micro-Tina' Tomatoes

Tomatoes (Lycopersicon esculentum Mill.) are one of the most widely consumed vegetables.  Tomatoes are studied extensively as models for fruit development and ripening research.  'Micro-Tina' tomatoes are a red fruited, dwarf cultivar with a compact growth habit, and may serve as a model crop for physiological and biochemical research.  Abscisic acid (ABA) plays regulatory roles in plant growth and development, in seed dormancy, and plant stress.  Recent studies have revealed physiological impacts in late stages of fruit development induced by increasing concentrations of ABA.  Changes in ABA concentration, along with increased ethylene activity improve fruit quality by increasing soluble sugars and carotenoids in the developing fruit.  Our objective was to study the effects of exogenous ABA on tomato phytonutrients and fruit quality.  ‘Micro-Tina’ tomatoes were grown in nutrient solution and ABA was applied to the solution just before flower initiation at concentrations of 0.0 (control), 0.4, 2.0, 10.0, or 50.0 mg ABA/L.  Fruit was harvested, graded and analyzed for mineral nutrients, soluble sugars, and carotenoid pigments.  There was no significant change in mineral nutrients with increasing concentrations of ABA.  However, there was a significant increase (P ≥ 0.05) in total soluble sugars.  Soluble sugars ranged from 57.03 to 101.28 mg/g dry weight (DW) and responded quadratically to increasing ABA treatments.  Fructose also followed a quadratic fit (P ≥ 0.05) to the data, and ranged from 37.76 to 50.08 mg/g DW.  Abscisic acid did not influence concentration of fruit tissue beta-carotene [0.53 mg/100 grams fresh weight (gfw)] or lutein (0.37 mg/100 gfw).  However, fruit tissue lycopene significantly increased (P ≥ 0.05) with ABA treatment concentrations, ranging from   9.18 to 14.75 mg/100 gfw.  As a result, this study shows exogenous ABA applications can significant increase fruit quality parameters in tomatoes.