Rice Genomics and Genetics 2024, Vol.15, No.3, 106-120 http://cropscipublisher.com/index.php/rgg 107 This study aims to study strategies for improving rice by utilizing the genetic resources of wild and cultivated Oryza species. The research emphasizes the importance of genetic diversity in rice improvement and the role of wild Oryza species as reservoirs of beneficial alleles. It highlights the use of biotechnological tools and methods to harness the genetic traits of wild species and discusses case studies of successfully incorporating wild rice genes into cultivated rice. Additionally, the study identifies the challenges of integrating wild genetic resources into breeding programs and outlines future research and development directions. By addressing these objectives, the study underscores the significance of wild Oryza species in rice improvement and offers valuable insights for sustainable agricultural practices to enhance rice productivity and resilience. 2 Genetic Resources in the Oryza Genus 2.1WildOryza species The genus Oryza includes a diverse range of species, serving as a vital genetic reservoir for rice improvement. It is primarily divided into wild and cultivated rice, both of which make significant contributions to rice breeding programs. Wild Oryza species exhibit significant genetic diversity and are distributed across various ecological niches worldwide. The genus includes 27 species, which have evolved over 15 million years, resulting in a wide range of adaptive traits (Mussurova et al., 2020). These species are found in diverse environments, from tropical to subtropical regions, and possess different genome types, such as AA, BB, CC, and others (Ricachenevsky and Sperotto, 2016). This extensive diversity makes wild Oryza species a rich source of genetic variation for improving cultivated rice. Wild Oryza species harbor numerous traits of interest that can be harnessed for rice improvement. For instance, Oryza longistaminata, a perennial wild rice, possesses traits such as rhizomatousness, disease resistance, and drought tolerance, which are valuable for enhancing the resilience of cultivated rice (He et al., 2014). Additionally, Oryza rufipogon, the closest wild relative of cultivated rice, has been shown to contain alleles that improve yield and other agronomic traits (Li et al., 2020). These wild species also exhibit traits related to metal tolerance and nutrient accumulation, which are crucial for improving the nutritional quality and stress tolerance of rice (Ricachenevsky and Sperotto, 2016). 2.2 CultivatedOryza species The domestication of rice began approximately 10 000 years ago, involving the selection of specific traits from wild ancestors to develop cultivated varieties. Oryza sativa, the most widely cultivated rice species, was domesticated fromOryza rufipogon (Ricachenevsky and Sperotto, 2016). The domestication process involved the selection of traits such as reduced seed shattering, increased grain size, and improved yield (Eizenga et al., 2017). Advances in genomics have provided insights into the genetic changes that occurred during domestication, revealing the loss of genetic diversity in cultivated rice compared to its wild relatives (Wambetugu et al., 2019). There are two major subspecies of cultivated rice: Oryza sativa ssp. japonica and Oryza sativa ssp. indica. Japonica varieties, such as Dianjingyou 1 and Yundao 1, are typically grown in temperate regions, while indica varieties, such as RD23, are more common in tropical areas (Zhang et al., 2022). Additionally, African rice (Oryza glaberrima) is another cultivated species that has been utilized for its resistance to biotic and abiotic stresses (Wambetugu et al., 2019). These cultivated varieties have been the focus of breeding programs aimed at improving yield, disease resistance, and other agronomic traits through the introgression of beneficial alleles from wild species (Zhang et al., 2021; Zhang et al., 2022). The genetic resources within the Oryza genus, encompassing both wild and cultivated species, offer a wealth of traits that can be leveraged for rice improvement. By utilizing the genetic diversity present in wild species and the advanced genomic tools available for cultivated varieties, breeders can develop rice cultivars with enhanced yield, resilience, and nutritional quality.
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