Abstract: A study on the interacion of 125 main millet varieties(strains) and 117 isolates of piricularia setariae based on the theory and method of interorganismal genetics was made from 1983 to 1985. It was found that this method of testing the cultivars with the population of pathogen approached move to the natural condition com-paried with the tranditional methnd by testing varietance with individual races respectively. Besides, we divided the region of main millet production into three ecological regions, namely the west ,eas t and north-cold mountianous regions according to the geography and meteorology of Shanxi, and studied the interaction of millet varieties and isolates of the pathogen with in each ecological regions. This work provided useful information for planning the deployment of millet cultivars in Shanxi province.

Key words: Millet blast, Frequency toxicity, Co-resistance to disease, Ecological region