Genotype and lighting environment impact petal tissue pigmentation in Tagetes tenuifolia

D. Kopsell, C. Belisle, H. Lowery, C. Whitlock, C.E. Sams
The carotenoid molecular structure allows for absorption of short-wave radiation resulting in pigment coloration from yellow to red. In chloroplasts, carotenoids function in a number of essential processes in photosynthesis; whereas in chromoplasts they are used to attract insect pollinators and seed dispersing herbivores. Carotenoids in petal tissues of ornamental specialty crops contribute to aesthetic value. However, carotenoids are extracted from petals of Tagetes species and used as carotenoid sources. Recently, edible flower Tagetes have been promoted as a salad garnish which can contribute valuable anti-oxidant carotenoids to the human diet. The objectives of these studies were to characterize the profiles and concentrations of petal tissue carotenoids among different T. tenuifolia genotypes and to determine the potential to increase carotenoid concentrations through simple LED lighting techniques. 'Lemon Gem', 'Tangerine Gem', and 'Red Gem' edible marigolds were grown in nutrient solution culture in a greenhouse environment at the University of Tennessee. Flowers were harvested after 60 days and measured for carotenoids. 'Red Gem' petals had the highest concentrations of α-carotene, β-carotene, lutein, zeaxanthin, antheraxanthin, violaxanthin, and neoxanthin, followed by 'Tangerine Gem' then 'Lemon Gem'. 'Lemon Gem' and 'Tangerine Gem' were grown in controlled environments at a total light intensity of 250 µmols m-2 s-1 during a 12-h photoperiod. Light quality treatments were established as: 1) fluorescent/incandescent light; 2) 10% blue (447±5 nm)/90% red (627±5 nm) LED light; 3) 20% blue/80% red LED light; and 4) 40% blue/60% red light-emitting diode (LED) light as sole source lighting. Petal carotenoid pigments in both genotypes were much higher under LED light, and were highest under 20% blue light. Both genetics and environmental conditions can be managed to maximize nutritionally important carotenoids in the petal tissues of T. tenuifolia.
Kopsell, D., Belisle, C., Lowery, H., Whitlock, C. and Sams, C.E. (2016). Genotype and lighting environment impact petal tissue pigmentation in Tagetes tenuifolia. Acta Hortic. 1134, 103-110
DOI: 10.17660/ActaHortic.2016.1134.14
α-carotene, β-carotene, blue light, light-emitting diode, LED, lutein

Acta Horticulturae