Races ofPhytophthora sojaein Argentina and Reaction of Soybean Cultivars

Race identification of Phytophthora sojae in soybean is reported for the first time in Argentina. Isolates from dying plants and from infested soils were collected during surveys of soybean fields in Pergamino County from 1989 to 1992. Race determination on 46 isolates was made by the hypocotyl puncture method using the North American differential set (Wells, Harlon, Beeson 80, Williams 79, PI 103091, Pella 86, Williams 82, PI 171442, Harosoy, Harosoy 32, and Altona) and two Canadian Harosoy isolines (Harosoy 13 and Harosoy 6272). All the isolates were race 1, virulent only on Harosoy. Most of 25 Argentina-grown cultivars tested by hypocotyl inoculation showed a susceptible reaction. Only Norki 555, Norki 641, Asgrow 2943, and RA 587 were resistant to this race