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ARS Home » Midwest Area » West Lafayette, Indiana » Crop Production and Pest Control Research » Research » Publications at this Location » Publication #173727
Title: PEROXIDASE ACTIVITY IN SOYBEANS FOLLOWING INOCULATION WITH PHYTOPHTHORA SOJAE

Author
item MELGAR, J - PURDUE UNIVERSITY
item ABNEY, THOMAS
item VIERLING, R - IN CROP IMP & PURDUE UNIV

Submitted to: Mycopathologica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/16/2005
Publication Date: 1/5/2006
Citation: Melgar, J.C., Abney, T.S., Vierling, R.A. 2006. Peroxidase activity in soybeans following inoculation with phytophthora sojae. Mycopathologica. 161(1):37-42.

Interpretive Summary: Soybean yield losses due to Phytophthora (PR) root rot occur regularly. This disease is potentially devastating in soybean varieties that do not have resistance. Two forms of resistance (whole-plant or race-specific resistance and root or partial resistance) are important for PR control. Soybean gene(s) known as "Rps" confer race-specific resistance to different infectious strains (races) of the PR fungus. Some of the new PR races are not controlled by the Rps1-k gene widely used in breeding programs for resistance to PR root rot. Development of improved technology to identify partial resistance in soybean progeny is needed to effectively combine the two forms of resistance in soybean varieties. An extensive study of peroxidase activity in soybean seedlings inoculated with PR races identified increases in soluble peroxidases that can be associated with the root resistance. The results provide soybean researchers insights into both whole-plant and partial or root resistance. This is the first report of an increase in peroxidase activity in soybeans with non-race specific resistance and the unique form of root resistance associated with the Rps2 gene. Information from this study will permit soybean researchers to select and recommend disease resistant soybean germplasm that can be used in breeding programs to minimize yield losses and will help farmers choose soybean varieties resistant to PR root rot.

Technical Abstract: The effects of race-specific resistance as conditioned by Rps genes (rps, Rps1-k, Rps2, Rps3, Rps6) in two genetic backgrounds (Williams & Harosoy) on accumulation of soluble peroxidases were determined by a soybean peroxidase capture assay (SPCA) after inoculation with P. sojae races 2, 7, or 25. Peroxidase activity increased in all isolines during the 72 hours after inoculation, but reactions varied depending on time after inoculation, genetic background, Rps gene and P. sojae race. Peroxidase activity was higher in race-specific resistant than in susceptible reactions at 72 hrs. after inoculation, except for plants with the Rps2 gene which confers a unique form of root resistance in addition to the whole plant race-specific resistance. Williams isolines had larger increases in peroxidase activity than Harosoy isolines when data were averaged across Rps genes, and was most evident when plants were inoculated with race 2. When soybeans were inoculated with race 7 Rps1-k resistant plants had the highest increase in peroxidase activity, but Rps2 susceptible plants had a significantly higher peroxidase activity than plants with rps, Rps3, and Rps6 that were also susceptible. Results from inoculations with race 25 were somewhat different, Rps2 resistant plants had the highest increase in peroxidase activity; however, plants with the Rps3 or Rps6 gene that were also resistant did not have a significantly higher peroxidase activity than susceptible plants with the rps or Rps1-k gene.