Floral biology of wild marigold (Tagetes minuta L.) and its relation to essential oil composition.

• Eleven floral developmental stages of Tagetes minuta L. (Wild Marigold) were identified each having distinct characteristic feature. • The floral biology of wild marigold suggests often cross pollinated breeding behaviour. • Significant variations in essential oil composition at each floral development stages were recorded. The (Z)-β-ocimene content was highest in inflorescence, while dihydrotagetone content was highest in foliage. • Study of pollination behavior of wild marigold is critical to decide the breeding strategies required for its improvement. Wild marigold (Tagetes minuta L.) is being commercially cultivated due to high demand of its essential oil in flavor and perfumery industry. Present study investigates pollination behavior, mechanism of pollination and floral developmental of wild marigold in to 11 stages each having distinct characteristic feature as observed by visual and light microscopy. Pollen production starts from stage-2, shape of pollen is spherical tricolpate and size varies from 0.025 - 0.031 mm. However, highest pollen availability and viability is observed at stage-6. Bilobed stigma protrude from the flowers at stage-7 indicating protandry. High bee activity is evident under open field conditions suggesting entomophilous mechanism of pollination. Based on viable seed formation and per cent germination, open field conditions are most suitable for good seed set as these conditions favor cross pollination. Despite poor seed set in self-pollinated condition germination percentage was not affected significantly. Floral biology of wild marigold suggests often cross pollinated breeding behaviour. Gas Chromatography - Mass spectrometry results showed significant variation in essential oil composition at foliage and inflorescence. The (Z)-β-ocimene (52.01 %) content was highest in inflorescence while dihydrotagetone (84.85 %) content was highest in foliage. Knowledge of pollination behavior of wild marigold is critical to decide the breeding strategies required for its improvement. [ABSTRACT FROM AUTHOR]