Field Crop 2024, Vol.7, No.6, 317-324 http://cropscipublisher.com/index.php/fc 318 traits such as the number of grains per panicle, grain weight, and tillers per plant (Li et al., 2024). Recent studies have identified numerous genes associated with these yield components, including those involved in the initiation and development of tillers and panicles (Xing and Zhang, 2010). Meta-QTL analyses have further refined the identification of stable genomic regions and candidate genes, such as those encoding cytochrome P450 and zinc finger proteins, which are crucial for grain yield regulation (Aloryi et al., 2022). 2.2 Advances in genetic engineering and genome editing for yield improvement Advancements in genetic engineering, particularly the use of CRISPR/Cas9, have enabled precise editing of yield-related genes in rice (Wang, 2024). This technology has been used to create mutants with enhanced yield traits by targeting genes like Grain number 1a (Gn1a) and DENSE AND ERECT PANICLE1 (DEP1), resulting in superior yield alleles (Huang et al., 2018). Additionally, CRISPR/Cas9 has been employed to edit genes in the cytochrome P450 family, leading to increased grain size and improved aroma without affecting other agronomic traits (Usman et al., 2020). These innovations highlight the potential of genome editing to significantly boost rice yield. 2.3 Challenges in translating genetic insights into practical applications Despite the progress in identifying yield-related genes and developing genetic engineering techniques, several challenges remain in translating these insights into practical applications. One major challenge is the complex interaction between genetic and environmental factors that influence yield traits, making it difficult to predict the performance of genetically modified varieties under diverse conditions (Figure 1) (Nutan et al., 2020). Additionally, the polygenic nature of yield traits means that minor-effect loci, which are difficult to identify and manipulate, play a significant role in yield outcomes (Su et al., 2021). Furthermore, ensuring the stable inheritance and expression of edited traits across generations remains a technical hurdle. These challenges necessitate continued research and development to effectively harness genetic insights for rice yield improvement. Figure 1 Schematic representation of factors determining crop yield in rice (Adopted from Nutan et al., 2020) Image caption: The three major factors and their components are listed, and cross-talk between them is indicated by the arrows. The inhibitory effect of environmental stress on yield is also indicated (Adopted from Nutan et al., 2020) 3 Agronomic Practices for High Yield 3.1 Optimized nutrient management strategies Optimized nutrient management is crucial for achieving high rice yields. Studies have shown that a balanced application of organic and inorganic fertilizers can significantly enhance rice productivity. For instance, a combination of 75% nitrogen through urea and 25% through vermicompost, along with micronutrients like ZnSO4 and FeSO4, has been found to maximize growth and yield. Additionally, site-specific nitrogen management and the timing of nitrogen application, particularly before panicle primordia formation, are critical for increasing spikelet numbers and overall grain yield (Bhuiyan et al., 2020). Adjusting nitrogen management to reduce late-stage applications can also improve rice quality and nitrogen use efficiency (Cheng et al., 2021).
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