Objective In order to determine the resistance characteristics and distribution of rice blast disease in rice landraces from Bulang minority in Yunnan.

Method Seedling-stage resistance evaluation and molecular characterization were conducted on 78 rice landraces using 31 functional markers targeting 24 blast resistance genes and 10 blast fungal strains.

Result Inoculation assays revealed that the 78 rice landraces exhibited resistance levels ranging from 40% to 100%, with an average resistance rate of 93.6%. Notably, 55 accessions (70.5%) demonstrated complete resistance (100%). Regional resistance patterns were observed as follows: Menghai County (99.00%) > Mojiang County (89.09%) > Shuangjiang County (80.59%). The resultes of Pathogen Virulence Profiling showed strains 08-16-6a-1 and HN-09-1c-7 displayed the highest virulence against Bulang landraces (11.54% susceptibility), where Menghai accessions being most susceptible to strains HN-09-1c-7 and 08-20-1a-1 (4.00% susceptibility), Mojiang landraces showed 36.36% susceptibility to strain 08-20-1a-1, Shuangjiang resources exhibited the highest susceptibility (52.94%) to strain 08-16-6a-1. Functional gene analysis revealed the presence of six blast resistance genes (Pi9, Pi5, Pita, Pikh, Pid2, and Pikm) in the Bulang rice landraces, with allele frequencies ranging from 73.08% to 84.62%. The Pid2 exhibited the highest overall frequency, while Pi9 showed the lowest. Regional variations were observed: In Menghai County, Pita and Pid2 predominated (84.62%), contrasting with the reduced prevalence of Pi9 (73.08%). Mojiang County displayed elevated frequencies of Pid2, Pi5, and Pi9 (84.62%), whereas Pita was least frequent (73.08%). In Shuangjiang County, Pid2, Pita, Pikm, Pikh, and Pi9 were dominant (84.62%), while Pi5 occurred at the lowest frequency (73.08%). Regression analysis demonstrated no significant correlations (P > 0.05) between these six genes and seedling-stage leaf blast resistance. Gene combinations accounted for 1.8% to 25.8% of resistance variability, with the Pid2+Pi5+Pikm+Pikh quartet showing the lowest explanatory power (1.8%) and the six-gene combination exhibiting the highest contribution (25.8%). However, no statistically significant synergistic effects were observed among the combined genes.

Conclusion The Bulang rice landraces of Yunnan possess robust and broad-spectrum blast resistance, predominantly mediated by the Pid2 gene. Thirty-eight accessions with complete resistance (100%) to 10 strains and co-occurrence of Pid2 and Pi9 alleles were identified. These accessions represent valuable genetic resources for diversifying the genetic basis of blast resistance in modern rice breeding programs.