Cytoplasmic Male Sterility

Summary

The video script delves into the concept of cytoplasmic male sterility (CMS), a vital technique in hybridization programs. CMS is controlled by plasmogenes in the cell's mitochondria or plastids, preventing self-pollination and encouraging cross-pollination, thereby eliminating the need for manual emasculation. It has been observed in over 150 plant species, including beans, beets, carrots, and wheat. CMS involves two types of cytoplasm: normal and sterile, with the latter producing male sterile plants. Inheritance of CMS is non-Mendelian, as it is passed down through the female parent's cytoplasm. It is applicable in crops where vegetative parts are valuable but not in seed-focused crops due to the inheritance of sterility. CMS can be introduced into a plant line through hybridization with a male sterile line carrying the CMS factors. The process involves backcrossing and maintaining the trait by crossing a male sterile line with an isogenic male fertility line. The resulting hybrid is always male sterile, ensuring the CMS trait's continuation.

Takeaways

• 🌱 Cytoplasmic male sterility (CMS) is a genetic trait found in the mitochondria or chloroplasts of plant cells that prevents self-pollination and encourages cross-pollination.
• 📈 CMS is a crucial technique in hybridization programs, eliminating the need for emasculation, a process where the male parts of a flower are removed to prevent self-fertilization.
• 🌾 Over 150 plant species, including common crops like beans, beets, carrots, onions, and wheat, have been reported to exhibit CMS.
• 🔬 There are two types of cytoplasm in CMS: normal cytoplasm, which produces male-fertile plants, and sterile cytoplasm, which results in male-sterile plants.
• 👩‍👧‍👦 Male sterility is inherited maternally because the female gamete contributes cytoplasm to the zygote, leading to a non-Mendelian inheritance pattern.
• 🚫 CMS cannot be used in crops where the seed is the valuable component, as the hybrid offspring would inherit the male sterile cytoplasm.
• 🌿 CMS can be utilized in crops where the vegetative parts have economic value, such as in certain types of plants where the leaves or stems are harvested.
• 🔄 The process of transferring CMS involves crossing a line with male-sterile cytoplasm and non-restorative genes with a line that has male-fertile cytoplasm and non-restorative genes.
• 🔄 The F1 generation resulting from the initial cross is then backcrossed for several generations to stabilize the desired traits.
• 🌟 Isogenic lines differing only in male sterility cytoplasm are used to maintain CMS, where the male-sterile line carries the factors for CMS and the male-fertile line provides functional pollen.
• 💫 The final hybrid is produced by crossing a male-sterile line with a male-fertile line, ensuring that the hybrid remains male sterile.

Q & A

What is cytoplasmic male sterility?

Cytoplasmic male sterility is a genetic condition governed by plasmogenes located in mitochondria or chloroplasts of the cell, which prevents self-pollination and promotes cross-pollination in plants.

Why is cytoplasmic male sterility important in hybridization programs?

It is important because it eliminates the need for emasculation, a process where the male reproductive parts of a plant are removed to prevent self-pollination, thus facilitating controlled cross-pollination.

How many plant species have been reported to exhibit cytoplasmic male sterility?

Cytoplasmic male sterility has been reported in over 150 plant species, including common crops like beans, beets, carrots, and wheat.

What are the two types of cytoplasm associated with cytoplasmic male sterility?

There are two types of cytoplasm: normal cytoplasm, which produces male fertile plants, and sterile cytoplasm, which produces male sterile plants.

How is male sterility inherited in plants with cytoplasmic male sterility?

Male sterility is inherited through the female parent because the female gamete contributes cytoplasm to the zygote, which contains the cytoplasmic factors responsible for male sterility.

Why doesn't the inheritance pattern of cytoplasmic male sterility follow Mendelian inheritance rules?

The inheritance pattern does not follow Mendelian rules because it is based on the transmission of genetic traits from the female parent only, rather than both parents as in classical Mendelian inheritance.

In what types of crops can cytoplasmic male sterility be utilized?

Cytoplasmic male sterility can be used in crops where the vegetative parts have economic value, but it cannot be used in crops where the seed is the valuable component, as the hybrid offspring would inherit male sterility.

How is cytoplasmic male sterility transferred to the female parent in a hybridization program?

It is transferred by crossing a line with male sterilized cytoplasm and non-restora genes with a male fertile line with normal cytoplasm and non-restora genes, followed by backcrossing for several generations.

What are isagenic lines in the context of maintaining cytoplasmic male sterility?

Isagenic lines are genetically identical lines that differ only in male sterility. They are used to maintain cytoplasmic male sterility by crossing a male sterile A line with an isagenic male fertile B line.

How is a hybrid produced using cytoplasmic male sterility?

A hybrid is produced by crossing a male sterile A line with a male fertile C-line. The resulting hybrid is always male sterile due to the presence of the male sterile cytoplasm.