PHENOTYPIC DIVERSITY IN Calendula officinalis L. REGARDING PLANT GROWTH, PHOTOSYNTHETIC TRAITS, FLOWER YIELD, AND OIL CONTENT

Abstract

Pot marigold (Calendula officinalis L.) is an annual herb-shrub distributed worldwide. It possesses multiple therapeutic applications as an antimicrobial, antioxidant, antiviral, anti-inflammatory, anti-cancer, and cosmetic agent. Despite its importance, its physiological traits, including photosynthetic parameters, plant growth kinetics, and oil content variation among phenotypes, remain unknown. Five contrasting phenotypes (S1 to S5), derived from a single variety, were characterized. Physiological variables evaluated included plant growth kinetics, growth rate indexes, A-C_i response curves, flower and oil yield, and oil chemical composition across eight harvesting dates. Phenotype S1 yielded the highest biomass because of its extended acceleration and deceleration growth stages during a longer period. Phenotype S1 also produced higher yields of harvested flowers and essential oil. Phenotype S2 also showed a high content of essential oils. This phenotypic diversity found in a single variety of pot marigold could be used for breeding this crop; for example, the crossing of S1 x S2 may produce F1 progenies with improved growth rates, flower yields, photosynthetic rates, and essential oil yield. Besides, phenotype S1 could be used directly for commercial planting.