Location: Horticultural Crops Production and Genetic Improvement Research Unit
Project Number: 2072-30500-002-002-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Sep 1, 2025
End Date: Aug 31, 2029
Objective:
The Pacific Northwest, which includes Oregon and Washington, produces more than half of the blueberries in the United States and nearly 100% of the nation’s processed blackberries. Both have high nutritional value but are very perishable with limited shelf-life. The plants must be harvested carefully and are greatly affected by various abiotic stresses, such as salinity, flooding, heat, cold, and excess light, that reduce productivity and ultimately threaten efforts to provide nutritional foods to U.S. consumers. The objective here is to test the use of biostimulants and growth regulators as a reliable means to improve stress tolerance in these crops. Applications can be made using standard spray or fertigation equipment readily available on commercial farms, negating the need for additional infrastructural costs associated with other mitigation strategies (e.g., evaporative cooling, shade cloth, etc.). If the results prove cost effective and mirror what has been observed in our preliminary glasshouse trials, we expect that 25-50% of the growers in the country will begin to implement the use of biostimulants or growth regulators to improve performance in their berry fields.
Approach:
Field experiments will be established in existing blueberry and blackberry plantings located at the OSU Lewis Bronw Farm in Prosser, OR and the North Willamette Research and Extension Center (NWREC) in Aurora, OR. The experiments will be arranged in a split-plot design with four replicates of three main plots and three subplots. The main plots will include two biostimulants (glycine betaine and a kelp extract) and two growth regulators (cytokinins and ethylene). These treatments were selected because they significantly improved the growth and physiology in multiple genotypes of juvenile raspberry and blackberry plants in previous glasshouse trials. Each will be applied at the highest recommended label rate as a foliar spray. The subplot treatments will include three timings of application (early, late, and continuous). Early applications will be done weekly between mid-May and early June to coincide with flowering, while late applications will be made weekly between mid-June and early July to coincide with fruiting and onset of high summer temperatures. Continuous applications will also be made weekly, but from mid-May through July, spanning the entire period between the early and late applications. Shields will be used to prevent drift between plots during application. Leaf samples will be collected periodically from each subplot, flash frozen, and stored for later determination of malondialdehyde (MDA) and peroxide content of trichloroacetic acid. These measurements will provide insights into oxidative damage and the stress response mechanisms observed across the treatments. Leaf samples will also be subjected to label-free quantification proteome analysis to assess any changes in expression and abundance of proteins and pinpoint specific pathways affected by biostimulant application. The identified proteins will be functionally annotated using the UniProt database, which will be used to search for the Gene Ontology analyses of each of the heat responsive proteins and identify their involvement in molecular, biological, and cellular processes associated with tolerance to damage from heat or excessive solar radiation. Additionally, standard measurements of chlorophyll fluorescence, CO2 assimilation, stomatal conductance, and midday stem water potential will be done to determine how the applied treatments affect photosynthesis and plant water relations. Afterwards, yield data will be collected once or twice a week during the entire harvest period (late-June to mid-July in blackberry and late July to mid-August in blueberry). During each harvest, a subsample of 30 berries will be analyzed for quality traits, including firmness, soluble solids, pH, and titratable acidity.