Marigold (Calendula officinalisL.) is a small perennial herbaceous cultivated plant of the Asteraceae family. Its inflorecences are big capitulums used for medicinal or culinary purposes. This species has shown genetic diversity in its chemical composition. The yellow and orange color of the flowers come from flavonoid and carotenoid pigments. In México there are not studies of the variation in carotenoid content in marigold flowers related to the harvesting dates and genotypes (1), when submitted to periodic capitulum harvests during the growing season. In this study we determined the total carotenoid concentration in floral capitulums of six selected genotypes of marigold, each harvested through ten successive cuts. Capitulums were collected every week for 10 weeks, and dried at 40 °C for 48h, and then milled to fine powder. The quantification of total carotenoids was done by spectrometry. The absorbance data were converted to concentrations (in mg/100 mg of dry weight), through the equation: β-carotene (mg/100 mL)= 0.216 x A663 -1.220 x A645 – 0.304 x A505 + 0.452 x A453.Significant differences (P < 0.05) were found among genotypes and harvesting dates, and also in the interaction, in the concentration of total carotenoids in capitulums. Genotypes M5 and M3 contained the highest concentration of carotenoids, in the average of ten harvesting dates, whereas those of least concentration were M4 and M6. The optimal dates of harvest which rendered the highest concentration of carotenoids, in the average of six genotypes, were F1, F3, F4, F7 and F9. Regarding the magnitude of effects, the genetic factor was 10 times higher than the harvesting date, thus evidencing the importance of the genetic variation.
Reference: [1] Kishimoto S., M. Takashi, S. Katsuhiko, O. Akemi. 2005. Bioscience biotechnology and biochemistry. 69: 2122 – 2128.
