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United States Department of Agriculture

Agricultural Research Service

Title: Frequently Isolated Races of Phytophthora Sojae Identified in Indiana Soybean Fields

item Abney, Thomas

Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: June 21, 1998
Publication Date: N/A

Technical Abstract: Several new races of Phytophthora sojae that cause root rot and extensive yield loss in soybeans were identified during the 1990s. Soil samples were randomly collected from soybean fields in 70 Indiana counties. Race data for the isolates of P. sojae infecting "Sloan" soybean seedlings in 1996 suggest that races 1, 3, 4, 7, 13, 25, 28, 33, and 44 occur most frequently. Previous data during the 1990s verify the nine races as dominant races in Indiana soybean fields. In contrast to reports during the 1970s, races of P. sojae were not unique to any one geographic region. The pathogen was detected in at least 50% of the soil samples from fields throughout the state. The Rps1-k gene, commonly used by breeders, confers resistance to races 1, 3, 4, 7, 13, and 44; however, additional genes (i.e., Rps3 or Rps6) are needed to develop soybeans with resistance to races 25, 28, or 33.

Last Modified: 4/18/2015
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