18th Nov 2021
Introduction to Marigolds
Diwali, a popular Hindu festival (mostly celebrated in India), has just passed by and the fragrance of marigold flowers has left its essence in the air.
Marigold is popularly used in India, to make rangolis during the Diwali festival and decorate houses during the marriage, rituals, or any other festival. Its utility is not only limited to decorations but is also used in traditional medicinal approaches to treat certain diseases or ailments.
Marigolds are rich in antioxidants, vitamin C, and antioxidants and hone some medicinal properties, such as anti-inflammatory, anti-cancer properties, and anti-spasmodic.
Marigolds are known for their fragrant scent and vibrant colors. They are popular in commercial space for their cut flowers and are known as the “herb of the sun”.
Scientifically, marigolds are called Tagetes, having different species in the family of Asteraceae. Tagetes genus has plant diversity ranging from annual, perennial, and herbaceous plants. They are native to America from the southwestern United States into South America.
There are 50 species of marigolds, but the most frequently grown ones, which regularly can be seen in garden spaces are:
- Tagetes erecta (African marigolds, American marigolds, or Mexican marigolds): It’s a herbaceous annual or perennial plant that grows to a height of 20-90 cm. It’s predominantly grown in America, Africa, and Mexico. They can thrive well under drought-like conditions.
- Tagetes patula (French marigolds): It’s native to Mexico and Guatemala. It’s an annual plant that grows to a height of 0.5 m (1.6 ft) and 0.3 m (1.0 ft) wide. They are smaller, bushier, and more compact than African marigolds. They grow well and survive in rainy seasons.
- Tagetes tenuifolia (signet marigolds): Its predominantly grown in Mexico, Peru, Columbia, and Central America. It’s an annual herb that grows to a height of 50 cm. It grows well in hot and dry conditions.
- Calendula officinalis (pot marigolds or English marigolds): Its native to southern Europe but also grown in southern England and other temperate regions of the world. It’s a perennial herbaceous plant that grows to a height of 80 cm. It’s not a true marigold but matches similar in appearance to marigold plants.
Cultivation and Care of Marigolds
Different species of marigolds support different seasons for their growth, which starts from spring to midsummer. The seeds are sowed when the soil is warm. The sprouting starts in a week and in 8 weeks the plant starts blooming.
Marigolds prefer warm weather. In shady, wet, moist, and cool areas, they become prone to powdery mildew and might not bloom well. Some marigolds can be easily grown using seeds, while, some are a tough nut. They require to be grown using young plants.
When the plants are established, it’s time to care and groom the plants for their better and bushier growth. You can prevent the singling of plants, by pinching off the upper part of the stem and removing the deadheads (faded flowers). Strictly avoid overwatering the plants, as it can cause their death.
Techniques to Propagate Marigolds
Marigolds have several applications:
- Use of cut flowers in decoration and rituals
- As an ingredient in traditional medicines
- For nematode control
- To add variety to the landscape
Conventionally, marigolds are grown either using herbaceous shoot-tip cutting or seeds. However, for rapid propagation and producing true-to-type plants, tissue culture is the most preferable technique. Further, they are also used to improve the quality of planting materials, and for safe and long-term maintenance of the germplasm of the plant.
In tissue culture, the explants that have been tested for the production of the plants include immature un-pollinated disc florets, proliferated adult plants and, leaf callus and suspension culture.
Tissue Culture of Marigold
The procedure to tissue culture marigold is taken from the study of Verma, Manjusha & Majumder, Jayoti & Singh, Dr. shiv & PRASAD, K & Kanwar, Paramjeet Singh. (2015). In vitro morphogenesis in marigold using shoot tip as explant. Indian Journal of Horticulture. 71. 82-86.
- Cut the shoot tip and in aseptic conditions, culture it on Murashige and Skoog (MS) medium.
- Surface sterilize the explant using carbendazim (0.1%), 8-hydroxy quinoline citrate (200 mg/l), and Indofil (0.1%) for 45 min, on a horizontal shaker (120 rpm).
- Then, treat the explants using mercuric chloride solution for 1-3 min.
- Wash the explants, three times, with sterilized distilled water.
- Inoculate a single shoot in each test tube having 7-8 ml MS media, supplemented with 30% sucrose and various combinations of BAP (1.0 mg/l) and GA3 (0.5 mg/l).
- Incubate the cultures in a growth chamber (25° ± 1°C) under cool white fluorescent lamps providing the light intensity of 47 μmol m-2s-1. The photoperiod was adjusted to a 16/8 h light and dark cycle.
- After the shoots are germinated, transfer them onto a fresh medium supplemented with BAP (2.0 mg/l), NAA (0.1 mg/l), and 30% sugar with 8.0 g/l agar.
- When after a few weeks micro shoots are developed, transfer them on a half-strength MS medium supplemented with 1.0 mg/l NAA and 1.0 mg/l IBA with 0.7% agar.
- Adjust the pH of the media to 5.8 and autoclave at 121 degrees celsius for 20 minutes.
- Maintain the cultures at 25 ± 1°C air temperature in a culture room with a 16-h photoperiod under the illumination of 20 μmol m-2s-1 photosynthetic photon flux density provided by cool-white fluorescent light.
- After 2-3 weeks, transfer the plants to glass jars, containing a mixture of sterile peat, vermiculite, and perlite (2:1:1), for root hardening.
- Then, gradually acclimatize the plants by loosening the cap of the cup and then eventually removing it.
- Transfer the plant to a plastic pot with potting mixture and keep it in the glasshouse at room temperature (25 to 30°C) under natural illumination at a photon flux density of 330 to 350 μmol m-2s-1.
- After 3-4 weeks, plants will be ready to transfer to normal condition.
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Tissue culture is a meticulous process. It requires high-grade equipment, chemicals, and equipment to perform the experiment. Here, PCT helps you to procure all your tissue culture requirements at an affordable cost. In the PCT store, you will get MS media, agar, gellan gum, plant growth regulators, culture vessels, and BiocouplerTM temporary immersion bioreactor.
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At PCT, you also get professional consulting services to get instant answers to your tissue culture queries. For Cannabis culturists, consulting services are available for both, on-site and off-site consultation.
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- Verma, Manjusha & Majumder, Jayoti & Singh, Dr. shiv & PRASAD, K & Kanwar, Paramjeet Singh. (2015). In vitro morphogenesis in marigold using shoot tip as explant. Indian Journal of Horticulture. 71. 82-86
- Misra, Pratibha & Datta, Subodh Kumar Datta. (1999). In vitro propagation of white marigold (Tagetes erecta L.) through shoot tip proliferation. Current science. 77. 1138-1140.
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