Objective In order to address the challenges posed by bacterial blight to the safety of rice production and to clarify the status of bacterial blight resistance genes in 72 rice germplasm materials.

Method The total DNA of 72 rice germplasm materials from the sea rice germplasm repository of Guangdong Ocean University was extracted. Use specific molecular marker techniques to conduct PCR and agarose gel electrophoresis for detection and analysis of the 8 known bacterial blight resistance genes (Xa1, Xa5, Xa7, Xa13, Xa21, Xa23, Xa26, Xa27). And the electrophoresis data were subjected to cluster analysis using the software NTsyspc 2.10e.

Result The 72 rice germplasm materials were all found to possess resistance genes against bacterial blight, and each of the materials carried at least 2 such resistance genes simultaneously. Among them, the germplasm materials R1141 and D2 simultaneously carry five resistance genes, namely Xa1, Xa5, Xa7, Xa23, and Xa26. There were 53 samples carrying all three resistance genes simultaneously, accounting for 73.61%. A total of 51 germplasm materials carried the same resistance gene combination, namely Xa1, Xa5, and Xa26. Xa1, Xa26, and Xa5 were detected with the highest frequencies, which were 98.61%, 93.06%, and 91.67% respectively. Cluster analysis divided 72 rice germplasm materials into 3 major categories: The Ⅰ category included 64 materials, all of which carried both the Xa1 and Xa26 resistance genes simultaneously; the Ⅱ category included 5 materials, all of which carried both the Xa1 and Xa5 resistance genes simultaneously; the Ⅲ category included 3 materials, all of which carried the Xa1, Xa7, Xa23, and Xa26 resistance genes simultaneously.

Conclusion The homogenization of bacterial blight resistance genes in rice germplasm materials is severe, and the polymorphism is relatively low. The proportion of materials carrying Xa1, Xa5 and Xa26 simultaneously is as high as 71%. However, there are only two germplasm materials carrying five resistance genes simultaneously, which can be used as source parents of disease-resistant genes and their innovative utilization should be strengthened. At the same time, efforts should be made to strengthen the protection of wild rice resources and local rice varieties resistant to bacterial blight, to preserve the diversity of rice germplasm, to discover more new genes for resistance to bacterial blight, and to widely utilize them in hybrid breeding to broaden the genetic background of rice resistance to bacterial blight, and to select more new materials that combine different combinations of disease-resistant genes.