Hybrid vigour and hybrid mimics in rice
- Publication Type:
- Thesis
- Issue Date:
- 2020
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Hybrid vigour, or Heterosis, is the phenomenon when the hybrid offspring has qualities in growth, survival and fitness superior to its parents. Heterosis has been applied in agriculture for decades, especially in the production of maize and rice, but the molecular mechanism of heterosis is not clear. The hybrid rice industry needs to produce fresh hybrid seeds for every planting, and farmers cannot reserve seeds for the next sowing. Previous studies indicated that heterosis could be associated with altered gene expression at early developmental stages, especially genes related to photosynthetic pathways. Hybrid mimics are stable F1-like lines, developed through recurrent pure breeding from F2 plants. Hybrid mimic lines have been developed in 𝘈𝘳𝘢𝘣𝘪𝘥𝘰𝘱𝘴𝘪𝘴. The hybrid mimics in 𝘈𝘳𝘢𝘣𝘪𝘥𝘰𝘱𝘴𝘪𝘴 have similar biomass as the F1 and are larger than the parents, and the increased biomass could be stably inherited to offspring. The objectives of this project were to develop hybrid mimic lines in rice and to investigate the relationship between heterosis at early developmental stages and photosynthesis.
In my program, two Chinese hybrid mimic lines were developed in cooperation with scientists from Sichuan Agriculture University. An Australian hybrid underwent recurrent selection for an F1 like phenotype to the F4 generation, results are promising, and hybrid mimics can likely be developed at the F5/F6 generation. The hybrid mimics enable farmers to reserve seeds for planting high yielding lines, avoiding purchasing hybrid seeds each planting season. The three hybrid lines all had biomass heterosis at the early seedling development stage. The early heterosis was associated with early expression of photosynthesis-related genes in hybrids and hybrid mimics. Physiological evidence that an earlier commencement of photosynthesis in hybrids than parents was collected in the Australian hybrids. The results suggested that the earlier photosynthesis in hybrids contribute to the establishment of early heterosis. The molecular mechanism resulting in the earlier photosynthesis process in hybrids may be the key to understanding the secret of hybrid vigour. Hybrid Mimics give a greater continuity to superior hybrids and should increase global food supply.
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