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ARS Home » Pacific West Area » Corvallis, Oregon » Horticultural Crops Disease and Pest Management Research Unit » Research » Research Project #442902

Research Project: Establishment and Cultivar-Specific Associations of Mycorrhizal Fungi in Newly-Turned Raspberry Fields

Location: Horticultural Crops Disease and Pest Management Research Unit

Project Number: 2072-22000-045-025-G
Project Type: Grant

Start Date: May 1, 2022
End Date: Oct 31, 2023

Objective:
1. Determine if raspberry plants have access to mycorrhizal fungi in fields that have recently been tilled and fumigated. Objective 2. Determine if availability of mycorrhizal fungi changes during the first three years that raspberry plants are in the field. Objective 3. Determine if mycorrhizal colonization differs across raspberry cultivars.

Approach:
Soil samples will be collected from three breeding fields managed by Northwest Plant Company (NW Plant Co.) that operate on a three-year turnover cycle, with field ages (time since turnover) ranging from 0-2 years at time of sampling. Working within this system provides a unique opportunity to track both mycorrhizal establishment and associations with multiple raspberry genotypes within the same field. Turnover includes tilling and fumigation with Telone C-35. In each field, samples will be collected from replicated plots of 'Meeker' and 'WakeHaven' as well as replicated plots of six novel cultivars, totaling 24 samples per field (8 cultivars per field x 3 reps) and 72 samples total. Each sample will be divided into three portions. Portion A will be transferred to paper bags and air dried for spore analysis. Portion B will be sifted and roots will be removed for measuring field colonization of mycorrhizal fungi. Portion C will be retained as inoculum for measuring mycorrhizal colonization potential of field soil in a greenhouse assay. Spores of mycorrhizal fungi from Portion A will be separated from soil using the sucrose-gradient method and counted directly using a dissection microscope. Data will be reported as number of spores per gram of dry soil. Field colonization of roots from Portion B will be assessed via the magnified intersections method (McGonigle et al. 1990). Roots will be cleared and stained with a fungal specific stain and presence/absence of mycorrhizal fungi will be quantified under 200x magnification. Data will be reported as percent of root intersections containing mycorrhizal fungi. Colonization potential will be measured by growing corn (Zea mays) in a greenhouse for six weeks with Portion C and nine additional control plants (72 samples + 9 controls = 81 pots). Corn is used in colonization potential studies because it forms mycorrhizae with a wide range of fungal species and it grows quickly, thus giving a good measure of primary colonization by field propagules, rather than measuring secondary colonization. At the end of six weeks, colonization of plants roots will be assessed using the methods described above. Extensions at the time roots are collected for abundance measurements via microscopy, subsamples will also be stored at -20'C. If the abundance data is interesting and funding allows, we would characterize mycorrhizal fungal communities via molecular methods by targeting the small subunit rRNA gene and aligning sequences against virtual taxa using the curated database MaarjAM. Crop data will be collected by NW Plant Co., including yield (tons/acre), berry firmness, berry weight, and berry Brix. Soil data will also be collected by NW Plant Co., but at the field rather than plot level, and including availability of nitrogen and phosphorus, pH, and organic matter content.