M.Sc. Seminar - GPB 582 (0+1)
SYNOPSIS
Harnessing hybrid vigour remains a powerful strategy to boost crop productivity in the face of rising food demands and climate uncertainties.¹ Precise control of pollination is fundamental to hybrid breeding, as it prevents self-pollination, encourages cross pollination, and ensures the genetic purity and vigour of improved crop varieties. Cross pollination mechanisms such as self-incompatibility and male sterility play a crucial role in producing high-yielding, resilient hybrids that contribute to sustainable and secure food systems.
Male sterility is one of the most reliable biological tools for enforcing cross-pollination. Genetic Male Sterility (GMS) offers a simple genetic route for emasculation but faces limitations due to its inheritance, as only about half the progeny are sterile when controlled by dominant or recessive genes, making it inefficient to maintain uniform sterile lines. Removing fertile plants is laborious and costly, while clonal propagation or tissue culture helps only in a few crops like ornamentals. To overcome this, breeders use genetic or cytogenetic methods and transgenic approaches that target pollen development genes for stable sterility. Cytoplasmic Male Sterility (CMS) is maternally inherited and documented in over 150 species. CMS results from mitochondrial DNA rearrangements that generate chimeric open reading frames (ORFs), which disrupt pollen development by altering nuclear–cytoplasmic interactions. Restorer (Rf) genes in the nucleus can counteract these ORFs, enabling controlled fertility restoration when required.² The extensive diversification and proven value of CMS systems make them indispensable tools for stable, large-scale hybrid seed production in a wide range of crops.
Self-incompatibility (SI) is a genetic mechanism in flowering plants that prevents self-fertilization and promotes outcrossing. It is classified into homomorphic and heteromorphic types based on floral morphology, homomorphic SI further divided into gametophytic (GSI) and sporophytic (SSI) systems, depending on whether the pollen’s haploid or diploid genotype determines incompatibility. GSI observed in Solanaceae and Papaveraceae involves style-mediated inhibition, while SSI found in Brassicaceae involves stigma-level rejection. Molecular mechanisms include S-RNase activity in GSI and ligand-receptor interactions in SSI.
The genetic pattern of SI in Oryza longistaminata has been studied using self-pollination and reciprocal cross-pollination. The findings indicated the presence of GSI which is regulated by OISS1, OISP and OISS2 genes expressed in stamens, pistil and in both stamens and pistil, respectively.³
Self-incompatibility and male sterility systems represent cornerstone innovations in plant breeding, offering precise control over fertilization and enabling efficient hybrid seed production. Unravelling the molecular basis of SI has opened new frontiers for its strategic manipulation, while systems such as CMS, CGMS and GMS continue to drive genetic gain and cytoplasmic studies in diverse crops. Emerging transgenic and hormone-inducible sterility technologies, though still evolving, hold immense promise for scalable and cost-effective hybrid breeding. Collectively, these tools not only enhance breeding efficiency and genetic diversity but also highlight the critical role of reproductive biology in advancing sustainable agriculture.
REFERENCES
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BOHRA, A., JHA, U. C., ADHIMOOLAM, P., BISHT, D. AND SINGH, N. P., 2016, Cytoplasmic male sterility (CMS) in hybrid breeding in field crops. Plant Cell Reports., 35(5): 967-993.
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RAO, M. K., DEVI, K. U. AND ARUNDHATI, A., 1990, Applications of genic male sterility in plant breeding. Plant Breed., 105(1): 1-25.
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LIAN, X., ZHANG, S., HUANG, G., HUANG, L., ZHANG, J. AND HU, F., 2021, Confirmation of a Gametophytic Self-Incompatibility in Oryza longistaminata. Front. Plant Sci., 12: 1655.
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