heterosis_vegetables_presenhhtation.pptx

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1. Heterosis Breeding in Vegetables Types, mechanisms, and facilitating mechanisms (male sterility, self-incompatibility, sex form) Prepared with diagrams and recent literature references

2. Outline Introduction to heterosis and importance in vegetable breeding Types of heterosis (mid-parent, better-parent, commercial heterosis) Genetic models: dominance, overdominance, epistasis Molecular and epigenetic basis of heterosis Facilitating mechanisms: male sterility, self-incompatibility, sex forms Practical breeding systems and examples in vegetables Case studies and recent research highlights (2021-2025) References

3. Introduction Heterosis (hybrid vigor): superior performance of F1 over parents Key trait targets in vegetables: yield, uniformity, disease resistance, quality Widely used in vegetables: tomato, cabbage, cucumber, pepper, onion

4. Types of Heterosis Mid-parent heterosis (MPH): F1 vs mean of parents Better-parent (heterobeltiosis): F1 vs superior parent Commercial heterosis: economic advantage in production

5. Measuring Heterosis Mid-parent heterosis (%) = ((F1 - MP)/MP) * 100 Heterobeltiosis (%) = ((F1 - BP)/BP) * 100 Statistical designs: RCBD, LsD trials for hybrid evaluation

6. Genetic Models Explaining Heterosis Dominance hypothesis: masking of deleterious recessives by dominant alleles Overdominance hypothesis: heterozygote advantage at specific loci Epistasis: favorable interactions between loci in hybrids

7. Genetic Models (schematic) Conceptual overlap: dominance, overdominance and epistasis contribute together Recent reviews integrate genomic and epigenetic evidence for mixed models.

8. Molecular Basis — Gene Expression Additive and non-additive gene expression patterns in hybrids Expression complementation: hybrid recovers beneficial expression levels Role of regulatory networks and transcription factors

9. Epigenetic Contributions DNA methylation and histone modifications alter gene expression in hybrids Small RNAs (siRNA, miRNA) can mediate parental allele expression biases Recent studies show RNA methylation and miRNA involvement (referenced)

10. Proteome & Metabolome Protein expression and metabolic pathways often show hybrid-specific profiles Metabolite complementation can improve growth and stress tolerance

11. Illustration — Yield Advantage Synthetic example showing F1 out-yielding both parents Actual vegetable trials commonly report 20-60% yield advantage depending on crop

12. Facilitating Mechanisms Male sterility systems (CMS, GMS, CGMS) enable efficient hybrid seed production Self-incompatibility systems promote outcrossing and hybrid seed set Sex form manipulation (gynoecy, monoecy, dioecy) used in some vegetables

13. Male Sterility — Types Cytoplasmic Male Sterility (CMS) — maternally inherited Genic Male Sterility (GMS) — nuclear genes control sterility Cytoplasmic-genic Male Sterility (CGMS) — interaction of cms and nuclear restorer

14. Hybrid seed production — using male sterility Stepwise: create/identify sterile line, cross with restorer/maintainer, produce F1 seed Widely used in crops like cabbage, onion, and some solanaceous vegetables

15. Male Sterility — Molecular Basis & Examples CMS often involves chimeric mitochondrial genes causing pollen abortion (e.g., orf variants) Restorer-of-fertility (Rf) nuclear genes counteract CMS; example: cabbage Ms-cd1 study (2023) GMS examples: tomato and cucumber recessive/sporophytic male sterility genes used in breeding

16. Self-Incompatibility (SI) Systems Sporophytic SI (SSI): common in Brassicaceae (e.g., some Brassica species) Gametophytic SI (GSI): common in Solanaceae and Rosaceae (S-RNase based) SI prevents selfing — useful for hybrid seed production but complicates seed set control

17. Self-Incompatibility Concept Pollen-pistil recognition by S-alleles leads to rejection of self pollen Breeders manipulate SI via S-allele management, bud pollination, or SI breakdown

18. Sex Forms and Breeding Gynoecy (female-only flowers), monoecy, dioecy — important in cucurbits (e.g., cucumber, melon) Gynoecious lines used to produce hybrids with higher fruit set and yield Sex form genes (e.g., CsACS2 in cucumber) are targets for manipulation

19. Example: Tomato Hybrid tomato: vigor for yield, uniformity, disease resistance Male sterility systems and grafting used in tomato hybrid production Molecular markers and genomic selection accelerate hybrid parent development

20. Example: Cabbage & Brassica CMS widely used in Brassica oleracea and B. rapa hybrids Ms-cd1 dominant male-sterile gene cloned in cabbage (2023) — useful for hybrid systems Restorer lines and maintainer lines are integral to CGMS systems

21. Example: Cucurbits Gynoecious lines (female-rich) used to boost hybrid seed and commercial fruit yield SI and sex form manipulation important in cucumber breeding Parthenocarpy and seedless varieties also exploited in some cucurbits

22. Example: Onion CMS and GMS systems used for hybrid onion seed production High heterosis reported for bulb yield and bolting resistance

23. Strategies to Exploit Heterosis Develop diverse heterotic groups and testers Use CMS/GMS systems for scalable hybrid seed production Apply genomics tools: GWAS, genomic selection, transcriptomics to predict heterosis

24. Predicting Heterosis — Tools Genomic prediction (GS) models trained on hybrid performance Transcriptome-based biomarkers and parental distance metrics can improve prediction Integrating epigenetic and metabolomic markers is an emerging approach

25. Recent Research Highlights (selected) Yu et al., 2021 — molecular basis of heterosis in vegetables (Hortic Res). Li et al., 2024 — molecular mechanisms of heterosis review (PMC). Cheng et al., 2023 — genic male and female sterility in vegetable crops (Hortic Res).

26. More Recent References (selected) Murase et al., 2024 — molecular mechanisms of self-incompatibility (PMC). Gu et al., 2024 — heterosis genetic dissection (Plant Physiology review). Singh et al., 2023 — genetic mechanisms for hybrid breeding in vegetables (PMC).

27. Practical Recommendations Characterize germplasm to form heterotic groups Adopt male sterility systems where possible to scale seed production Use marker-assisted selection for restorer/sterile loci and integrate GS for performance

28. Challenges & Limitations SI and CMS systems can have instability or environmental sensitivity Maintaining uniformity and seed production cost in vegetables Regulatory and seed-market constraints for hybrid adoption in some regions

29. References (selected) Yu, D. et al. 2021. Molecular basis of heterosis and related breeding strategies (Hortic Res). Li, Z. et al. 2024. Molecular mechanisms of heterosis and its applications (PMC). Cheng, Z. et al. 2023. Genic male and female sterility in vegetable crops (Hortic Res). Murase, K. et al. 2024. Molecular mechanisms of self-incompatibility (PMC). Gu, Z. et al. 2024. Unlocking the mystery of heterosis (Plant Physiol review). Singh, H. et al. 2023. Genetic mechanisms for hybrid breeding in vegetable crops (PMC).

30. Acknowledgements & Contact Presentation generated with programmatic diagrams and literature synthesis (2021-2025). For full PDFs and raw images listed in references, see the cited papers (links provided in the chat response). Contact: Mohit — for modifications, images, or localisation to specific vegetable crops.