Irrigation effect on yield and desirable metabolites of pot marigold ( Calendula officinalis L.) genotypes

Managed irrigation water may induce industrially desirable metabolites in pot marigold. Thus, the effects of three irrigation regimes (35% [I1], 60% [I2], and 85% [I3] depletion of the available soil water) on the yield, irrigation water use efficiency, and secondary metabolite content of nine pot marigold genotypes were examined during 2015 to 2016 and 2016 to 2017 growing seasons in Ahwaz, Iran. Carotenoid, alkaloid, and flavonoid contents as well as antioxidant activity increased under I2 and I3 treatments, while phenol content increased under I2 and reduced under I3 treatments. The Isfahan2 genotype produced the highest flavonoid content under I1 and I2 and the highest phenol content under I1, I2, and I3. The Zen-gold genotype produced the highest flavonoid content under I3. The highest carotenoid content was obtained under I1 and I2, while the highest alkaloid content was detected under I3 in Tehran. The Gitana genotype contained the highest carotenoid content under I3, while Isfahan1 produced the highest alkaloid content under the I1 irrigation regime. Gitana under I2 and Zen-gold under I3 had the highest antioxidant activity. Gitana under I1 and I3 and Candy-man under I2 had the highest extract content. The Candy-man genotype produced the highest petal yield and extract yield under I1, I2, and I3 irrigation regimes. The results from our findings suggest that the production of secondary metabolites in pot marigold was dependent on metabolite, genotype, and irrigation regime. The results also demonstrate that drought had positive effects on measured metabolites, especially under the I2 irrigation regime, but a negative effect on dry petal yield and extract yield. Thus, the number and amount of irrigation could be reduce while metabolite contents increase under selected irrigation regimes and genotypes.