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ARS Home » Midwest Area » St. Paul, Minnesota » Plant Science Research » Research » Research Project #433283

Research Project: Improving Alfalfa Yields and Stand Life Through New Strategies for Managing Seed Rot and Seedling Damping Off

Location: Plant Science Research

Project Number: 5062-12210-003-23-T
Project Type: Trust Fund Cooperative Agreement

Start Date: Jan 1, 2018
End Date: Jun 30, 2019

The goal of the project is to develop management methods for reducing damage from pathogens causing seed rot and seedling damping off of alfalfa. The specific objectives are: 1. Evaluate fungicides and biological agents for their activity against seed rot pathogens of alfalfa. 2. Examine interactions between Sinorhizobium meliloti used for nodulation of alfalfa with the fungicides and biologicals found to be effective against seed rot pathogens. 3. Measure the resistance in experimental germplasm that has undergone one cycle of selection for resistance to Pythium species causing seed rot and damping off.

For Objective 1, commercially available fungicides used for seed treatments in other crops will be tested for efficacy against Pythium, Fusarium, and Rhizoctonia strains causing seed rot and seedling damping off of alfalfa using in vitro agar plate assays. Commercial (and potentially experimental) biological materials used for managing soil borne pathogens will also be tested. Fungicides will be added to agar media at different rates and the concentrations causing 50% growth reduction of pathogens will be identified. Biological materials will be cultured on agar plates and then challenged with pathogens. Zones of growth inhibition will be measured to identify those with the highest activity. Materials showing activity against pathogens will be used at different rates to treat alfalfa seeds of a susceptible cultivar. Treated seeds will be planted in soil infested with known pathogens and into field soil known to have high levels of seed rot and damping off for greenhouse tests. Seedling emergence, root health, and plant dry weight will be measured. For Objective 2, the interaction of fungicides, biologicals and Sinorhizobium will be evaluated in vitro and in soil. A collection of S. meliloti strains will be tested for sensitivity to fungicides and biologicals showing activity against pathogens in agar plate assays. The fungicides and biological will also be used for seed treatments alone and in combinations with S. meliloti. Treated seed will be tested in infested soil in greenhouse assays. Seedling emergence, root health, nodule number and dry weight and plant dry weight will be measured. For objective 3, in previous research three germplasms were selected for resistance to Pythium strains causing seed rot and seedling damping off. Seeds are currently be produced by intercrossing plants within each germplasm. Seed will be collected from each female parent. Subsamples from each female will be tested for resistance to Pythium in a plate assay. Seeds from the most resistant lines will be mixed in equal proportions and used in soil assays to measure seedling emergence, root health, and plant dry weight.