1. Recover P. sojae from fields within each state and characterize for pathotype and genetic diversity.
• Isolate collection of >2000 isolates (200 isolates per state)
• Improved understanding of diversity of pathotypes across region will inform of areas were Rps genes can and cannot be deployed
• Improved knowledge of genetic diversity across the region

2. Evaluate the new sources of resistance to these regional populations.
• Identify Rps genes that are effective for each of collaborating states
• Improved deployment of soybean varieties with Rps genes across the region will result in fewer losses due to Phytophthora root rot

3. Recover P. sansomeana from fields within each state and characterize for host range, genetic diversity.
• Isolate collection of >600 isolates (50 isolates per state)
• Improved understanding of phenotypic and genetic diversity within this species
• Improved knowledge of distribution and prevalence of the pathogen across the region
• Knowledge of effectiveness of Rps genes against pathogen

4. Establish sensitivities (EC50) values for P. sojae and P. sansomeana isolates recovered from fields towards the new active ingredients ethaboxam, strobilurin, and oxathiapiprolin fungicides.
• Establish baseline levels of fungicide sensitivity to ethaboxam and oxathiapiprolin before these active ingredients are widely used.
• Monitor sensitivity to strobilurins and detect reduced sensitivities that may have occurred in past few years based on published data (Broders et al 2007; Matthiesen et al 2016; Rojas et al, submitted) due to widespread use in seed treatments containing strobilurins.
• Information on placement of active ingredients across the region

5. Comparison of new seed treatments on varieties with different resistance packages (Rps gene(s)/partial resistance) in field trials.

6. Evaluation of potential herbicide interactions with the development seed rot and stand loss.
• Field trials will be established at least 2 locations per state during 2017 and 2018.
• Effect of different resistance packages on soybean disease and midseason PRR.
• Detect interactions between pre-emergence herbicides and watermold pathogens that increase risk of stand loss due to seedling disease
• Economic benefits/costs for the each management tactics.

7. Development of Crop Protection Network Outputs on the Management of Phytophthora spp. that infect soybean in the North Central and Ontario regions.
• Development of management guide

Updated May 1, 2020:
Phytophthora sojae is present in many fields across the North Central region and Ontario, Canada, and had been managed very successfully with the deployment of Rps genes and partial resistance. However, there are an increasing number of reports where varieties sold with Rps genes are no longer effective towards the regional population or lack sufficient levels of partial resistance. The consequence is stand loss, lower yields and added weed pressure. The shift towards virulence in a number of the P. sojae populations was confirmed in these studies. To date, 1345 isolates of P. sojae have collected along with 142 of P. sansomeana and 191 Pythium spp. From the isolates of P. sojae, 1142 have been pathotyped. The number of Rps genes that a specific isolate can cause disease on continues to increase across the region, with several states reporting isolates that cause disease on all of the Rps genes. The implications to this finding are that it will be difficult if not impossible to rotate genes. These populations of P. sojae, once they are adapted are maintaining virulence in the field. There are regional differences, similar to what was reported earlier but Rps1a, Rps1c, and Rps1k were largely ineffective across the region. Additionally, these populations are sensitive to the primary fungicide seed treatments, metalaxyl, ethaboxam and oxathiopiprolin for those areas that evaluated. Projects that are still in progress is to evaluate newer sources of resistance and the out reach piece through Crop protection Network and regional evaluations of data following last year’s tough growing season.

View uploaded report

Many of the common and historically deployed Rps genes have limited effectiveness in the states that collected P. sojae and evaluated this trait in these studies. There were regional differences. Partial resistance should be utilized in areas where this disease is prevalent. All of the seed treatments were effective in protecting soybeans from the isolates of both P. sojae and P. sansomeana that have been tested to date.