Rice Genomics and Genetics 2024, Vol.15, No.6, 309-319 http://cropscipublisher.com/index.php/rgg 310 2 Genetic Diversity in Rice 2.1 Overview of genetic resources in rice Rice (Oryza sativa L.) is a staple food crop with a rich genetic diversity, encompassing both cultivated and wild varieties. The genetic resources of rice include traditional landraces, modern cultivars, and wild relatives such as O. rufipogon and O. nivara, which are crucial for breeding programs due to their inherent traits like disease resistance and drought tolerance (Sangeetha et al., 2020). The domestication and subsequent diversification of rice have led to the development of various subgroups, including indica, aus, and basmati, each adapted to different ecological niches (Figure 1) (Zhou et al., 2022). The genetic diversity within these groups is essential for the continued improvement and adaptation of rice to changing environmental conditions. Figure 1 Subgroup differentiation of Oryza sativa in the evolution process. The japonica rice (circle in the center) was domesticated first from Oryza rufipogon, then divided northward as temperate japonica, and south ward as tropical japonica. The indica was descent from hybridization between japonica and local wild populations or proto-indica. The aus was derived from the hybridization between indica and local wild populations, while the basmatic was derived from hybridization between japonica andaus. Weedy rice strains de-domesticated from and coexisted with cultivated subgroups, and frequently crossed with wild populations (if present) or landraces during their evolution process (Adopted from Zhou et al., 2022) 2.2 Importance of genetic diversity in breeding Genetic diversity is a cornerstone of successful breeding programs as it provides the raw material for selection and improvement of desirable traits. High genetic variability among rice genotypes allows breeders to select for traits such as yield, disease resistance, and stress tolerance (Nie et al., 2022). For instance, the utilization of genetic diversity has led to the development of new restorer lines and hybrid varieties that exhibit improved agronomic performance (Awad-Allah et al., 2022). Moreover, the introgression of beneficial alleles from wild relatives into cultivated varieties has been instrumental in enhancing traits like pest resistance and environmental adaptability. The conservation and exploitation of genetic diversity are thus critical for the sustainability and resilience of rice production systems.
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