Physiological Races of Phytophthora sojae in Iran and Race –Specific Reactions of Some Soybean Cultivars

Phytophthora root and crown rot of soybean is known as a destructive disease of soy-bean both through out the world and in Iran. Physiologic races of Phytophthora soja were determined in this research and also a fast, accurate and simple method for inoculation of soybean to test race specific resistance. During the years　۲۰۰۱-۴, infected soybean plants at different growth stages were collected from different areas and ۲۲ isolates of P. sojae were recovered using PARPH medium. Physiological races of the pathogen were deter-mined on differential seedling lines by the hypocotyl inoculation method. Ten seedlings from each differential line grown in a ۱۰-cm pot were inoculated under greenhouse condi-tions (۲۵ºC) by a ۱۰-۱۴ days old fungus (LBA medium). The reaction of the seedlings was classified after ۵-۶ days as resistant (۷۰% or more of seedlings alive) or susceptible (۷۰% or more of the seedlings killed). Most isolates were identified as race one, six as race three, one as race four and one as a putative race ۱۳. Race-specific resistance of the ۶۰ cultivars towards race three was determined. Some of them such as ‘TMS’, ‘Maverick and ‘Williams ۸۲’ were considered as resistant cultivars. All experiments were repeated three times.

Keywords:

Phytophthora soja , Physiological races , Race-specific resistance