Rice Genomics and Genetics 2024, Vol.15, No.2, 83-93 http://cropscipublisher.com/index.php/rgg 87 3.3 Advances in genomic technologies and their impact on understanding domestication Recent advances in genomic technologies have significantly enhanced our understanding of rice domestication pathways. The application of genomic sequencing and analysis is crucial for identifying the genome-wide characteristics of rice domestication. For instance, studies on wild rice (Oryza rufipogon) and Asian cultivated rice (Oryza sativa) have elucidated the genetic diversity and evolutionary history of these species, providing insights into the domestication process. One of the key breakthroughs is the use of genome-wide association studies (GWAS) and single nucleotide polymorphism (SNP) combinations. These tools enable researchers to map complex traits and understand the genetic structure of rice. For example, a study utilizing 1 536 SNP sets from 395 diverse rice varieties revealed significant genetic differences between the indica and japonica subspecies, supporting the theory of at least two independent domestication events. Similarly, another GWAS involving 44 100 SNP variations in 413 germplasms discovered numerous common variations affecting various complex traits, highlighting the rich genetic structure of O. sativa (Zhao et al., 2010). Integrated genomic approaches have facilitated the study of hybrid vigor loci in hybrid rice, which are crucial for yield heterosis. These studies have revealed the genomic structure behind rice heterosis, further enhancing rice breeding programs. The use of multi-locus analyses and population genomics has also provided deeper insights into the domestication and evolution of Chinese rice, indicating independent domestication events for the indica and japonica subspecies from different rice populations (Wei et al., 2012). In addition to these advances, biotechnological tools have facilitated the transfer of beneficial genes from wild species into cultivated rice. For example, genes conferring resistance to biotic and abiotic stresses have been successfully introgressed from wild species into rice, demonstrating the potential of wild species as reservoirs of beneficial traits. The introduction of the bacterial blight resistance gene (Xa21) fromO. longistaminata into various rice varieties exemplifies this potential (Zhao et al., 2011). 4 Environmental and Ecological Factors 4.1 Influence of climate and geography on domestication The domestication of rice (Oryza sativa) has been significantly influenced by climatic and geographical factors. Phylogeographic analyses of the wild ancestors of cultivated rice (Oryza rufipogon) indicate that domestication events occurred in different geographical regions. Indica rice is believed to have been domesticated south of the Himalayas, including regions of eastern India, Myanmar, and Thailand, while japonica rice was domesticated in southern China. This geographical distribution underscores the role of regional climates in shaping the pathways of rice domestication. Global climate change, particularly the increase in nighttime temperatures, has also affected rice yields. High nighttime temperature (HNT) stress has been shown to reduce rice yields, with the impact being more pronounced during the rainy season compared to the dry season. This demonstrates that climatic factors continue to influence rice cultivation and productivity (Jia et al., 2017). 4.2 Adaptation of rice to different environments Rice exhibits exceptional adaptability to a wide range of environmental conditions, which is crucial for its extensive cultivation. Genetic analysis of domestication traits in rice has shown that selection for traits such as reduced seed shattering, seed dormancy, and synchronized seed maturation has enabled rice to thrive in diverse agricultural environments. Additionally, adaptation to different thermal conditions, including cold and heat tolerance, is essential for the geographic expansion of rice cultivation (Schaarschmidt et al., 2020). The application of compounds such as gamma-aminobutyric acid (GABA), glutamic acid (Glu), and calcium chloride (CaCl2) has been proven to enhance the cold tolerance of rice seedlings, further demonstrating the species' ability to adapt to various environmental stresses. These adaptations allow rice to be grown in both temperate and tropical regions, making it a versatile crop (Zhu et al., 2007).
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