|
Download PDF
Chapter List
Hybrid Breeding – Chapter List
- Fundamentals of Heterosis
- Evolutionary and Genetic Basis of Heterosis
- Genetic Theories of Heterosis
- Biometrical Basis and Estimation of Heterosis
- Inbreeding and Inbreeding Depression
- Genetic Distance and Prediction of Heterosis
- Heterotic Pools and Parental Improvement
- Male Sterility in Hybrid Breeding
- Self-Incompatibility and Hybrid Development
- Hybrid Seed Production Systems
- Commercial Exploitation and Maintenance Breeding
- Fixation of Heterosis
- Apomixis and Organellar Heterosis
- Hybrid Breeding in Major Field Crops
- Hybrid Breeding in Oilseed Crops
PDF Preview {Click on Me}
Syllabus
Content: Historical aspect of heterosis, nomenclature and definitions of heterosis; Heterosis in natural population and inbred population; Evolutionary aspects – Genetic consequences of selfing, sibbing and crossing in self-and cross-pollinated and asexually propagated crops; Pre-Mendelian and Post-Mendelian ideas – Evolutionary concepts of heterosis; Genetic theories of heterosis – Physiological, Biochemical and molecular factors underlining heterosis; theories and their estimation; Biometrical basis of heterosis. Prediction of heterosis from various crosses, inbreeding depression, coefficient of inbreeding and its estimation, residual heterosis in F2 and segregating populations, importance of inbreeding in exploitation of heterosis – case studies.; Relationship between genetic distance and expression of heterosis, case studies; Divergence and genetic distance analyses, morphological and molecular genetic distance in predicting heterosis; Development of heterotic pools in germplasm/ genetic stocks and inbreeds, their improvement for increasing heterosis. Male sterility and use in heterosis breeding; Male sterile line creation and diversification in self-pollinated, cross pollinated and asexually propagated crops; Creation of male sterility through genetic engineering and its exploitation in heterosis; Maintenance, transfer and restoration of different types of male sterility; Use of self-incompatibility in development of hybrids. Hybrid seed production system: 3-line, 2-line and 1-line system; Development of inbreeds and parental lines- A, B and R lines – functional male sterility; Commercial exploitation of heterosis, maintenance breeding of parental lines in hybrids; Fixation of heterosis in self, cross and often cross pollinated crops, asexually/ clonally propagated crops, problems and prospects; Apomixis in fixing heterosis-concept of single line hybrid; Organellar heterosis and complementation. Hybrid breeding in wheat, rice, cotton, maize, pearl millet, sorghum and rapeseedmustard, sunflower, safflower and castor oilseed crops and pigeonpea.
Frequently Asked Questions.
Frequently Asked Questions (FAQs) on Hybrid Breeding
1. What is hybrid breeding?
Hybrid breeding is a plant breeding approach in which genetically diverse parents are crossed to produce F1 hybrids that exploit heterosis or hybrid vigour for improved yield, quality, resistance and adaptability.
2. What is heterosis?
Heterosis, or hybrid vigour, refers to the superior performance of an F1 hybrid compared with its parents for one or more desirable traits.
3. Who coined the term heterosis?
The term heterosis was coined by George H. Shull in 1914 to describe the phenomenon of increased vigour associated with hybridization.
4. What are the major types of heterosis?
The major types are mid-parent heterosis, heterobeltiosis and standard heterosis. They compare the F1 with the parental mean, better parent and standard check, respectively.
5. What is inbreeding depression?
Inbreeding depression is the reduction in vigour, fertility, yield or other fitness-related traits caused by increased homozygosity resulting from mating between related individuals or repeated self-pollination.
6. What is the relationship between inbreeding and heterosis?
Inbreeding increases homozygosity and may expose deleterious recessive alleles, causing inbreeding depression. Crossing genetically diverse inbred lines restores heterozygosity and can produce heterosis in the F1.
7. What are the major genetic theories of heterosis?
The major theories include the dominance hypothesis, overdominance hypothesis and epistasis hypothesis. Pseudo-overdominance is also used to explain heterosis caused by linked genes with complementary effects.
8. What is the dominance hypothesis of heterosis?
The dominance hypothesis proposes that favourable dominant alleles from one parent mask deleterious recessive alleles from the other parent, resulting in improved performance of the heterozygote.
9. What is the overdominance hypothesis?
The overdominance hypothesis proposes that the heterozygous genotype at a locus can perform better than either corresponding homozygote. In simplified form, Aa > AA or aa for the relevant trait.
10. What is genetic distance in hybrid breeding?
Genetic distance is a measure of genetic divergence between two genotypes or populations. It can be estimated using morphological, biochemical or molecular data and may help in selecting diverse parents for hybrid breeding.
11. Does greater genetic distance always result in higher heterosis?
No. Genetic distance may be associated with heterosis, but the relationship is not always strong or linear. Combining ability, gene action, heterotic group membership and specific parental interactions also influence hybrid performance.
12. What are heterotic groups?
Heterotic groups are groups of genetically related breeding materials that show predictable and complementary hybrid performance when crossed with members of another heterotic group.
13. What is male sterility?
Male sterility is the inability of a plant to produce functional or viable pollen while retaining female reproductive function. It is widely used to facilitate hybrid seed production by preventing self-pollination.
14. What are the major types of male sterility used in hybrid breeding?
Major types include genetic male sterility (GMS), cytoplasmic male sterility (CMS), cytoplasmic-genetic male sterility (CGMS), environment-sensitive male sterility (EGMS), chemical male sterility and functional male sterility.
15. What are A, B and R lines in hybrid breeding?
In the three-line CMS system, the A line is male sterile, the B line is the maintainer used to maintain the A line, and the R line is the restorer that restores fertility in the F1 hybrid.
16. What is the three-line system of hybrid seed production?
The three-line system uses A, B and R lines. The A line is maintained through A × B and commercial hybrid seed is produced through A × R. The B and R lines are generally maintained separately.
17. What is the two-line system of hybrid seed production?
The two-line system uses an environment-sensitive male-sterile line, such as a photoperiod-sensitive or thermo-sensitive genic male-sterile line. The same female line can be maintained under fertile conditions and used for hybrid seed production under sterile conditions.
18. What is apomixis and why is it important in hybrid breeding?
Apomixis is a form of asexual seed reproduction in which the normal sexual process is bypassed. It is important because it has the potential to maintain the genetic constitution and heterosis of a superior hybrid across generations.
19. Which crops are important examples of commercial hybrid breeding?
Important examples include maize, rice, pearl millet, sorghum, cotton, sunflower, rapeseed–mustard, safflower and castor. The hybrid breeding system differs according to the reproductive biology of each crop.
20. What is the main objective of hybrid breeding?
The main objective of hybrid breeding is to exploit heterosis by combining desirable genes from genetically diverse parents to develop superior F1 hybrids with high yield, quality, resistance, adaptability and stability.
Complete Tutorial Of How to Download
Video:- Scroll down past the product specifications.
- Tap Download Icon or scroll down to the countdown box.
- Wait for the "Starting Download in 10 seconds..." countdown to finish.
- You will be redirected to the Link2Unlock page.
- Tap the red 🔔 Subscribe button.
- YouTube will open to the @AgriXCulture channel. Tap Subscribe.
- Return to your browser tab.
- The button will update to Complete and show Unlock Progress 1 / 1.
- The Download now button will become active.
- Tap the blue Download now button.
- Select your Google Account and tap OK.
- The file will open in Google Drive.
- Tap the top-right menu (⋮) and choose Download for offline access.
The information and educational content published on Agrobotany is provided for general educational and informational purposes only. Our aim is to help students, educators, and agriculture learners understand various concepts in agriculture and related subjects in a simple and accessible manner.
While we make reasonable efforts to ensure that the information provided on this website is accurate, clear, and useful, Agrobotany does not guarantee that all information is complete, current, or error-free. Syllabi, recommendations, agricultural practices, scientific information, government policies, examination patterns, and institutional requirements may change from time to time.
Students are advised to verify important academic, examination, regulatory, agricultural, or technical information with official sources such as ICAR, agricultural universities, government departments, examination authorities, textbooks, and other recognized institutions before relying on it for academic or professional purposes.
The content available on Agrobotany should not be considered a substitute for official textbooks, university study material, professional advice, laboratory guidance, or instructions issued by competent authorities.
Agrobotany shall not be held responsible for any loss, damage, academic outcome, or other consequence arising from the use of or reliance upon information published on this website.
Some content may be simplified for easier understanding and learning. Therefore, examples, explanations, calculations, terminology, and descriptions may not always represent every possible academic or practical situation.
Copyright and ContentAll original website materials, including written content, graphics, designs, and other resources, are intended for educational purposes. Unauthorized reproduction, redistribution, or commercial use of copyrighted material is prohibited. Where third-party materials or references are used, reasonable efforts are made to acknowledge their respective sources and rights holders.
By using Agrobotany, you acknowledge and agree that you use the information provided on this website at your own discretion and responsibility.
Last Updated: August 2026
