In Laos, 92 races of rice blast disease were identified; each race can cause the disease in rice. Worldwide, only 23 resistance genes have been identified and available for use. In Laos, only one resistance gene (Piz) with resistance to Lao blast isolates has been identified, and it is believed that this gene may be broken down by rice blast isolates in the future. A study was therefore undertaken to identify potential rice blast resistance genes in Lao traditional rice varieties which have been 
conserved in the Lao national genebank. From among 211 Lao traditional rice varieties, 10 varieties were identified as having resistance to Lao blast isolates, indicating that these varieties carry resistance genes. These 10 varieties might therefore be potentially promoted in rice growing areas where rice blast disease is a chronic production constraint, especially in the wet-season cropping environment. The 10 varieties might also potentially be used for the identification of novel genes carrying resistance to rice blast. The resistant traditional varieties were originally collected from the same areas where rice blast is a chronic problem. It would appear that genes carrying resistance to rice blast coevolved with the development of the disease. Varieties collected from areas where rice blast disease was not present, were always susceptible to the disease. Four resistance genes were identified: Pita2 gene which was found in IRBLta2-Re and IRBLta2-Pi; Pi9 gene found in IRBL9-W; Pish gene found in IRBLsh-S; and Piz gene which was found in IRBLz-Fu. These genes were identified as having greatest resistance to Lao blast isolates, and will therefore be used in the Lao breeding program to develope multiline resistance to 
blast in the future.

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