Cytoplasmic Male Sterility

Elakkuvan S.

19 May 202303:15

Summary

TLDRThe 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.

Outlines

00:00

🌱 Cytoplasmic Male Sterility in Plant Hybridization

This paragraph delves into the concept of cytoplasmic male sterility (CMS), a vital technique in plant hybridization programs. CMS is controlled by plasmogenes in the mitochondria or chloroplasts, preventing self-pollination and encouraging cross-pollination. The paragraph explains that CMS is not governed by classical Mendelian inheritance but follows a non-Mendelian or cytoplasmic inheritance pattern, as it is inherited maternally through the female gamete. The script also highlights that CMS has been identified in over 150 plant species, including common crops like beans, beets, carrots, and wheat. The paragraph discusses the practical application of CMS in crops where vegetative parts are economically valuable, but notes its limitation in seed-based crops due to the inheritance of male sterility by the offspring. It outlines the process of transferring CMS through hybridization by crossing a line with male sterilized cytoplasm with one having male fertile cytoplasm and non-restora genes. The resulting F1 plants are male sterile, and the process of maintaining CMS through backcrossing and using isogenic lines is described.

Mindmap

Keywords

💡Cytoplasmic Male Sterility (CMS)

Cytoplasmic Male Sterility is a genetic condition in plants where the male reproductive parts are non-functional. This is crucial to the video's theme as it is the main subject being discussed. CMS is controlled by genes in the cytoplasm, specifically in the mitochondria or plastids, which is a departure from the usual nuclear genetic control. The script mentions that CMS prevents self-pollination and encourages cross-pollination, which is vital for hybridization programs.

💡Plasmogenes

Plasmogenes refer to genetic elements within the cytoplasm, particularly in the mitochondria or plastids, that are responsible for CMS. The term is central to understanding how CMS is inherited and functions, as it is these genes that dictate the sterile phenotype. The script indicates that CMS is governed by these plasmogenes, setting the foundation for the discussion on CMS.

💡Hybridization Program

A hybridization program is a systematic approach to breeding plants to combine desirable traits from different parent plants. The video's theme revolves around the use of CMS in such programs. CMS is an essential technique in these programs because it eliminates the need for emasculation, a process where the male reproductive parts are removed to prevent self-pollination, thus facilitating controlled cross-pollination.

💡Self-Pollination

Self-pollination is the process where a plant's male and female reproductive organs are pollinated by the same plant. The script mentions that CMS prevents self-pollination, which is significant because it ensures that the plant can only be cross-pollinated, leading to the desired hybrid offspring in a controlled breeding program.

💡Cross-Pollination

Cross-pollination is the transfer of pollen from the male reproductive organ of one plant to the female reproductive organ of another plant. The video discusses how CMS promotes cross-pollination, which is essential for creating hybrids with specific, combined traits from different parent plants.

💡Normal Cytoplasm

Normal cytoplasm refers to the cellular material of plants that does not contain the genes responsible for CMS. The script distinguishes between normal cytoplasm and sterile cytoplasm, with the former producing male fertile plants. Understanding this concept is important as it contrasts with sterile cytoplasm and explains the inheritance of CMS.

💡Sterile Cytoplasm

Sterile cytoplasm contains the genetic factors that result in male sterility. The script explains that plants with sterile cytoplasm produce male sterile plants, which is a key concept in the video as it directly relates to the CMS trait and its inheritance.

💡Non-Mendelian Inheritance

Non-Mendelian inheritance refers to genetic patterns that do not follow the traditional rules of inheritance established by Gregor Mendel. The video script states that the inheritance of CMS does not follow classical Mendelian inheritance rules, which are based on the transmission of genetic traits from both parents. This is significant because it highlights the unique mode of inheritance associated with cytoplasmic traits.

💡Isagenic Lines

Isagenic lines are genetically identical lines of plants that differ in only one trait. In the context of the video, isagenic lines differ only in their male sterility cytoplasm. The script mentions that CMS is maintained by crossing a male sterile A-line with an isagenic male fertility line, which is crucial for the breeding program to maintain the desired CMS trait.

💡Male Sterile A-Line

The male sterile A-line is a specific type of plant line that carries the cytoplasmic factors responsible for male sterility. The video script explains that this line is used in hybridization programs to transfer CMS to the female parent by crossing with a male fertile line. Understanding the role of the A-line is important for grasping the process of creating and maintaining CMS in plants.

💡Male Fertile C-Line

The male fertile C-line is a plant line that is used to provide functional pollen for fertilization in a hybridization program. The script mentions that a hybrid is produced by crossing a male sterile A-line with a male fertile C-line, resulting in a male sterile hybrid. This concept is key to understanding how CMS is utilized in controlled breeding to produce specific hybrid plants.

Highlights

Cytoplasmic male sterility is an essential technique in hybridization programs.

It is governed by plasmogenes located in mitochondria or pleuroplast.

Prevents self-pollination and promotes cross-pollination.

Eliminates the need for emasculation in hybridization.

Reported in over 150 plant species including common crops.

There are two types of cytoplasm: normal and sterile.

Normal cytoplasm produces male fertile plants.

Sterile cytoplasm produces male sterile plants.

Inheritance is through the female parent due to cytoplasmic contribution.

Does not follow classical Mendelian inheritance rules.

Inheritance is described as non-Mendelian or cytoplasmic.

Useful in crops where vegetative parts have economic value.

Not suitable for crops where seed is a valuable component.

Transferred to female parent by crossing with male sterile cytoplasm.

F1 generation is backcrossed for six to seven generations.

A and B lines are isagenic, differing only in male sterility.

Maintained by crossing male sterile A line with male fertility B line.

Hybrid is produced by crossing male sterile A line with male fertile C line.

Hybrid offspring are always male sterile.