Inheritance of Blast Resistance of a U. S. Rice Variety, Dawn

A gene analysis of a U. S. variety Dawn with blast resistance was carried out in a combination with a search for a method to identify genes included in a given foreign variety at an early stage in the use of the variety to breeding for disease resistance. For gene analysis, the mutant method was com-bined with the frequency distribution curvemethod. Three known genes, Pi-a, Pi-i and Pi-k, and additional unknown gene (s) which was not allelic to Pi-z, Pi-zt and Pi-ta were found in Dawn. In this analysis, distribution curve of the frequency of lines plotted on the number of intermediate and susceptible plants per F3 line of the cross Dawn×Shin 2 was used more effciently than the curve on the number of susceptible plants per line.