Effects of exogenous abscisic acid application on carotenoids and fruit quality in 'Micro-tina' tomatoes
Barickman, T. C., C. E. Sams, and D. A. Kopsell.  2012.  Proceedings of the Plant Growth Regulation Society of America 2011 Annual Meeting, pp. 42-43, Chicago, IL.

Tomatoes (Lycopersicon esculentum Mill.) are one of the most widely consumed vegetables and are a staple of many people worldwide. Tomato fruit are studied extensively as models for fruit development and ripening research. 'Micro-Tina' tomatoes are a red fruited, dwarfed cultivar with a compact growth habit, making it excellent for physiological and biochemical greenhouse research. Abscisic acid (ABA) is known for its regulatory role in plant growth and development, seed dormancy, and stress conditions. Recent studies have shown a pattern of change in late stages of fruit development induced by increasing concentrations of ABA. Changes in ABA concentrations, along with increasing activity of ethylene and other fruit ripening enzymes, increase tomato phytonutrient content and fruit quality by increasing soluble sugars and carotenoids in the developing fruit. Carotenoids are lipid soluble pigments found in many specialty crops that can provide health benefits such as reducing cancers, cardiovascular disease and certain eye diseases when regularly consumed in the diet. Therefore, our objective was to study the effects of exogenous ABA on tomato phytonutrients and fruit quality. ‘Micro-Tina’ tomatoes were grown in 10 L reservoirs filled with a complete nutrient solution, and ABA was added to the solution just before flower initiation. Abscisic Acid was applied in concentrations of 0.0 (Control), 0.4, 2.0, 10.0, 50.0 mg ABA/L. Fruit was harvested, graded and analyzed for yield, mineral nutrients, soluble sugars, and carotenoid pigments. Total yield and weight of red ripe fruit decreased with increasing concentrations of ABA. There were no statistically significant changes in mineral nutrient concentrations with increasing concentrations of ABA. However, there was a significant increase in total soluble sugars in ABA treatments 0.4, 2.0 and 10.0 mg ABA/L, with an average increase of 15% when compared to the control treatment. Soluble sugars were affected significantly at the 50.0 mg ABA/L with a 20% decrease. Lycopene was significantly affected at 0.4 mg ABA/L with a 33% increase in concentration. Lutein was increased with increasing concentrations of ABA in the nutrient solutions by an average of 20% when compared with the control treatment. Therefore, this study shows exogenous ABA applications up to 10.0 mg ABA/L significantly increase phytonutrient concentrations and fruit quality in red ripe tomatoes.