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ARS Home » Pacific West Area » Salinas, California » Crop Improvement and Protection Research » Research » Research Project #444853

Research Project: Aerial Dispersal of Fusarium oxysporum f. sp. fragariae and the Airborne Microbiome on the Central Coast of California

Location: Crop Improvement and Protection Research

Project Number: 2038-22000-019-045-S
Project Type: Non-Assistance Cooperative Agreement

Start Date: Sep 25, 2023
End Date: Dec 25, 2026

Objective 1. Characterize the epidemiological role of airborne dispersal by Fusarium oxysporum f.sp. fragariae. Objective 2. Characterize seasonal variation in soil, foliar, and airborne bacterial communities associated with commercial strawberry production systems.

We will establish cyclone-based spore traps at multiple locations in strawberry-producing regions of California. These will be regularly sampled and DNA extracted from each timepoint, and the abundance of Fusarium oxysporum f. sp. fragariae quantified from DNA extracts. Each spore trap will be placed near a weather station that monitors temperature, humidity, precipitation, windspeed, and barometric pressure. The spore traps will be maintained for a period of three years and pathogen abundance compared with environmental conditions to identify the conditions that are necessary and conducive to spore production. Spore traps will also be established in and around strawberry fields with: 1) a history of Fusarium wilt, and 2) a susceptible variety being cultivated. The spore traps will be placed at regular distances from the affected fields to assess the distance of spread, including in locations that are miles away from strawberry producing regions. Nearby strawberry fields will be monitored for signs of Fusarium wilt that could affect these results. The data will be analyzed to determine maximum distances for aerial spore dispersal. This in-field monitoring will be paired with controlled experiments testing the potential for aerial and water-borne dispersal. Fusarium oxysporum f. sp. fragariae conidia from sporodochia will be mechanically transferred to unwounded and wounded leaves, petioles, and crowns of healthy strawberry plants. Destructive sampling will be used to quantify the rate of spread (if any) from inoculated surfaces. Some plants will remain unsampled for a period of 12 weeks (or longer, if necessary) to determine if wilt disease symptoms can be caused by above-ground infections. This study will evaluate if bacteria colonizing strawberry plants are derived from soil or aerial microbiomes. Seasonal sampling will be conducted at strawberry ranches in the Watsonville/Salinas strawberry production region of California. Paired soil and foliar samples will be collected from individual plants. Air samples will be collected using spore traps within the same strawberry fields. Bacterial communities will be characterized from extracted DNA using standard 16S rRNA amplicon sequencing and established bioinformatic methods. Similarity and taxonomic overlap among bacterial communities from soil, foliar, and aerial samples will be evaluated using multivariate statistical methods.