Ogura’s Parental Medium: A Vital Tool in Plant Tissue Culture
In the realm of plant tissue culture, selecting the appropriate medium is crucial for successful growth and development of plant tissues or cells under sterile, in vitro conditions. One such specialized medium commonly used in research and in breeding programs is Ogura’s Parental Medium (OPM). This medium has gained recognition for its pivotal role, particularly in the field of cytoplasmic male sterility (CMS) studies, hybrid breeding, and somatic embryo development.
In this post, we’ll dive deeper into the specifics of Ogura’s Parental Medium, explore its composition, and understand its key applications in modern plant tissue culture.
What is Ogura’s Parental Medium?
Ogura’s Parental Medium (OPM) is a specially formulated medium primarily used for the in vitro culture of Brassica species, which include economically important crops such as cabbage, broccoli, turnip, and canola (oilseed rape). Named after the Japanese botanist H. Ogura, who extensively worked on cytoplasmic male sterility (CMS) genetics in these crops, the medium helps facilitate the growth and regeneration of explants—such as somatic embryos, callus cultures, and isolated protoplasts.
In plant breeding, Ogura’s Medium is frequently used for embryo rescue and facilitating somatic hybridization processes, enabling the transfer of important agronomic traits, such as cytoplasmic male sterility, from one species to another. CMS is a trait that is of great importance in hybrid seed production, as it allows for the generation of hybrid seeds without the need for manual emasculation (removal of male parts) of flowers during cross-pollination.
Ogura’s Parental Medium can support the development of complex plant structures from undifferentiated cells, making it a prerequisite for plant biotechnological approaches.
Formulation of Ogura’s Parental Medium (Per Litre)
The recipe for Ogura’s Parental Medium is designed to meet the nutritional needs of the plant tissues and provide them with an environment conducive to growth and differentiation. Below is the list of standard chemicals and nutrients needed to make 1 liter of Ogura’s Medium:
Macronutrients:
- NH₄NO₃ (Ammonium Nitrate): 1650 mg
- KNO₃ (Potassium Nitrate): 1900 mg
- CaCl₂ · 2H₂O (Calcium chloride dihydrate): 440 mg
- MgSO₄ · 7H₂O (Magnesium sulfate heptahydrate): 370 mg
- KH₂PO₄ (Potassium dihydrogen phosphate): 170 mg
Micronutrients:
- FeSO₄ · 7H₂O (Ferrous sulfate heptahydrate): 27.8 mg
- Na₂EDTA (Disodium ethylenediaminetetraacetate): 37.3 mg
- KI (Potassium iodide): 0.75 mg
- H₃BO₃ (Boric acid): 6.2 mg
- MnSO₄ · H₂O (Manganese sulfate monohydrate): 22.3 mg
- ZnSO₄ · 7H₂O (Zinc sulfate heptahydrate): 8.6 mg
- Na₂MoO₄ · 2H₂O (Sodium molybdate dihydrate): 0.25 mg
- CuSO₄ · 5H₂O (Copper sulfate pentahydrate): 0.025 mg
- CoCl₂ · 6H₂O (Cobalt chloride hexahydrate): 0.025 mg
Vitamins:
- Thiamine-HCl (Vitamin B1): 0.1 mg
- Pyridoxine-HCl (Vitamin B6): 0.5 mg
- Nicotinic Acid: 0.5 mg
- Glycine: 2 mg
- Myo-Inositol: 100 mg
Amino Acid:
- L-Glutamine: This is sometimes added to assist the growth of protoplast cultures at approximately 50 mg/L.
Growth Regulators (Cytokinins + Auxins):
- 6-Benzylaminopurine (BAP / BA): 0.1–1 mg (varies based on explant type)
- Naphthaleneacetic Acid (NAA): 0.01–0.1 mg
- Indole-3-acetic Acid (IAA): 0–1 mg (optional, depending on the protocol)
- 2,4-Dichlorophenoxyacetic Acid (2,4-D): 0.5–1 mg (used in some protocols for callogenesis)
Other Supplements:
- Sucrose: 30 g (as a carbon source)
- Agar: 7-8 g (if solid medium is desired), or you can use gellan gum for a higher clarity medium.
pH Adjustment:
- The pH of the medium should be adjusted to 5.8 before autoclaving at 121°C for 20 minutes to sterilize it.
Applications of Ogura’s Parental Medium
Somatic Embryogenesis and Protoplast Culture:
Ogura’s Parental Medium is excellent for promoting somatic embryogenesis—a process where plants can be regenerated from non-reproductive tissues. Protoplast (cell without cell walls) cultures and regenerations are also supported by this medium due to the balanced nutrient concentrations.
Cytoplasmic Male Sterility (CMS) Studies:
CMS is an essential trait in Brassica hybrid breeding, as it eliminates the tedious manual process of emasculating flowers to create hybrids. Ogura’s medium is particularly valuable for the Ogura CMS system, which is used to produce CMS hybrids in Brassicaceae crops.
Embryo Rescue:
When embryos from interspecific crosses are aborted due to incompatibilities, Ogura’s Parental Medium can be used as the growth medium for rescuing these embryos and allowing them to mature into viable plants.
- Regeneration from Explants & Callus Induction:
This medium provides the essential nutrients for tissue explants (such as leaf discs, stem segments, or root tissues) to generate undifferentiated callus tissue. The mode of growth can then be directed towards plantlet regeneration using appropriate growth regulators that are added.
Conclusion
Ogura’s Parental Medium (OPM) provides an essential basis for studying the regeneration and manipulation of Brassicaceae species and is invaluable in hybrid seed production programs that leverage cytoplasmic male sterility. The medium’s optimized formulation for Brassica crops ensures a suitable environment for protoplast culture, embryo rescue, and in vitro regeneration, making it a key tool in modern plant biotechnology.
Whether you are working on fundamental plant research, crop improvement, or commercial hybrid seed production, having the right tools, such as Ogura’s Parental Medium, can make a world of difference in achieving desirable outcomes.
References:
- Ogura H. Studies on the male sterility in Brassica crops and its application in hybrid breeding. (Original work on CMS system).
- Standard plant tissue culture manuals and protocols for Brassica explants.