Molecular Microbiology Research 2024, Vol.14, No.6, 277-289 http://microbescipublisher.com/index.php/mmr 278 The aim of this review is to explore the genetic diversity of blast resistance in paddy rice and upland rice. By understanding the genetic basis of resistance in these rice types, we aim to identify key resistance genes and quantitative trait loci (QTLs) that can be utilized in breeding programs to develop rice varieties with enhanced resistance to M. oryzae. We also seek to contribute to the broader understanding of plant-pathogen interactions and the molecular mechanisms underlying blast resistance in rice. Ultimately, the synthetic knowledge from this review will support the development of more resilient rice cultivars, ensuring food security and sustainable agricultural practices. 2 Understanding Rice Blast Disease 2.1 Causal agent: Magnaporthe oryzae Rice blast is the world's most serious rice disease affecting the safe production of rice, caused by the infestation of the rice blast fungus. This pathogen has emerged as a model organism for studying plant-pathogen interactions due to its complex infection mechanisms and significant impact on rice yield (Liu et al., 2013). M. oryzae infects rice plants by forming specialized structures called appressoria, which facilitate the penetration of the host plant's surface (Martin-Urdiroz et al., 2016). The fungus then proliferates within the plant tissue, deploying effector proteins that suppress plant immunity and promote fungal growth (Figure 1) (Oliveira-Garcia et al., 2023). 2.2 Symptoms and impact on rice yield The symptoms of rice blast disease include the appearance of lesions on various parts of the rice plant, such as leaves, stems, and panicles. These lesions can be elliptical or diamond-shaped with a grayish center and dark brown margins (Liang et al., 2018). In severe cases, the disease can lead to the complete destruction of the rice crop, significantly reducing yield. The impact of rice blast on yield is profound, as it can cause up to 50% yield loss in susceptible rice varieties under favorable conditions for the pathogen (Chen et al., 2018). The disease not only affects the quantity of the rice produced but also its quality, leading to economic losses for farmers and affecting food security (Liu et al., 2013; Martin-Urdiroz et al., 2016). 2.3 Historical perspective on blast disease management The prevention and control methods of rice blast include the treatment and selection of seeds, the scientific control of cultivation density, the strengthening of water and fertilizer management in the field, the elimination of bacterial sources, the cutting off of transmission routes, the use of chemical agents to prevent and control, etc., but some chemical agents will produce fungicide resistance to pathogens. Therefore, the development of blast-resistant rice varieties has been a cornerstone of disease management. This approach involves the identification and incorporation of resistance genes (R genes) into rice cultivars. Advances in molecular genetics and genomics have facilitated the discovery of numerous resistance genes and quantitative trait loci (QTLs) associated with blast resistance. Genome-wide association studies (GWAS) have identified several loci that contribute to resistance, providing valuable insights for breeding programs. Despite these efforts, the genetic diversity and adaptability of M. oryzae continue to pose significant challenges, necessitating ongoing research and the development of integrated disease management strategies (Figure 2) (Kang et al., 2016; Sheoran et al., 2021; Yan et al., 2022). Understanding the biology and impact of M. oryzae, along with historical and contemporary management practices, is crucial for developing effective strategies to combat rice blast disease and ensure global food security. 3 Genetic Basis of Blast Resistance 3.1 Resistance (R) genes identified in upland and paddy rice Resistance (R) genes play a crucial role in providing rice plants with the ability to resist blast disease caused by the fungus M. oryzae. Over the years, numerous R genes have been identified and characterized. Since the first genetic study for rice blast in 1922, 118 genes have been mapped and 28 genes have been cloned (Ashkani et al., 2016). The Pi2 cluster on chromosome 6 has been reported for the four successfully cloned genes (Pi2, Pi9, Pi-gm and Piz-t) (Meng et al., 2020). Among the 27 mapped genes on chromosome 11, six genes (Pik, Pik-h, Pik-m,
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