The research team has completed the microscopic analysis of the growth of the Hawaii 94-1 and Taiwan 80-2 ASR isolates on plants carrying Rpp3. Plants containing Rpp3 are resistant to Hawaii 94-1 and susceptible to Taiwan 80-2. The samples that were collected cover a seven-day time course spanning early infection, development of lesions, and sporulation. The growth of both isolates is the same in Rpp3 plants through 48 hai. At 72 hai, there are significantly more haustoria made by the Taiwan 80-2 isolate (susceptible) when compared to the Hawaii 94-1 isolate (resistant). Haustoria are specialized cells formed in close association with soybean cells. The difference in formation of haustoria is one of the first signs that the Rpp3 resistance has become activated, and this timing suggests that something produced by the Hawaii 94-1 haustoria as they form or shortly thereafter is being recognized by the Rpp3 plant and causing disease resistance responses to be activated. This 72 hour time point coincides with the gene expression data as the point at which Rpp3-mediated defenses become strongly activated in response to the Hawaii 94-1 isolate. These defenses subsequently limit the growth of Hawaii 94-1 as compared to Taiwan 80-2. We have initiated the microscopic analyses of ASR growth and development during the Rpp4 resistance response. Preliminary analysis shows that the development of ASR and timing of resistance in Rpp4 plants is much like Rpp3 plants suggesting that they have similar mechanisms for recognizing and limiting ASR growth.