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[Objective] The present paper aimed to explore the pathogenicity and dominant physiological groups and physiological races of Magnaporthe oryzae in Guangxi, analyze avirulence genes, find out the composition and distribution of physiological races and avirulence genes, providing reference for resistance breeding and variety promotion. [Method] Pathogenicity of 128 M. oryzae single spore isolates from 4 rice growing regions of southern Guangxi (Guinan), central Guangxi (Guizhong), northern Guangxi (Guibei) and alpine region were deter- mined by artificial spraying inoculation on the 7 unified identification of varieties in China and 26 near-isogenic lines (NILs) that contained only one resistance gene. (Result) Among the 128 rice blast strains, the proportion of strong pathogenic strains was 60.16%. The 128 M. oryzae strains could be divided into 7 groups and 26 physiological races, and the dominant group was ZB with a frequency of 69.53%. Dominant physiological races were ZB13 and ZB,, whose frequencies were 25.00% and 14.84%. Virulence frequency of the tested isolates ranged from 28.12% to 100.00%. Among them, the virulence frequency of the isolates group to resistance genes Pik, Pikm, Pil and Pi9 was lower, with frequencies of 28. 12%, 28.91%, 35.94% and 37.50%, respectively. Avirulence genes corresponding to the tested resistance genes were detected in the collected rice blast fungi, and 15 avirulence genes were detected in the four regions. Avirulence genes Aur-Pia (1), Aur-Pia(2), Aur-Pii, Aur-Pik, Aur-Pib, Aur-Pit, Aur-Pish (2), Aur-Pi3(1), Aur-Pi5 (1), Aur-Pil2(t) and Avr-Pi19(t) occurred at a frequency less than 20.00%. Most of isolates contained 5, 6, 7, 8, 10 avirulence genes with combination frequency of 19.53%, 11.72%, 11.72%, 15.63% and 10. 16% in the tested strains. [Conclusion] Rice blast fungi in Guangxi from 2021 have strong pathogenicity. The dominant physiological group is ZB and dominant physiological races are ZB13 and ZB9. Avirulence genes Aur-Pia (1), Avr-Pia (2), Aur-Pii, Aur-Pik, Aur-Pib, Aur-Pit, Avr-Pish (2), Aur-Pi3 (1), Aur-Pi5(1), Aur-Pil2(t) and Aur-Pil9(t) occurr at low frequency, which suggests that resistance genes corresponding to the avirulence genes should not be suitable for applying rice breeding and variety distribution in Guangxi. [ABSTRACT FROM AUTHOR]

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