Document Type

Thesis - Open Access

Award Date

2016

Degree Name

Master of Science (MS)

Department / School

Plant Science

First Advisor

Peter Sexton

Second Advisor

Michael Lehman

Abstract

Arbuscular mycorrhizal fungi (AMF) are obligate symbionts that form a mutualistic relationship with approximately 80% of terrestrial plant species. These obligate symbionts have a generally beneficial effect on their host such as increased nutrient acquisition, better tolerance to biotic and abiotic stresses, and the improvement of soil qualities. Due to the recent, widespread use of seed applied fungicides on row crops in the U.S. Midwest, there are concerns that the fungicides will inhibit these beneficial mycorrhizae. This study was conducted to evaluate what effect different commonly used seed applied fungicides have on AMF in the presence of different varieties of corn, soybean, and oat hosts grown in eastern South Dakota.
Preliminary experiments were performed to determine local crop varieties that were most responsive to forming relationships with AMF using soybean (Glycine max L.) and oat (Avena sativa L.); corn (Zea mays L.) was later added to the study. The most responsive oat and soybean varieties, plus the corn varieties, were treated with either one of three different fungicides (Raxil MD, Stamina F3 Cereals, or Evergol Energy for oat; CruiserMaxx Advanced, Evergol Energy SB, or Vibrance for soybean; Cruiser Extreme, Stamina, or Trilex for corn) or were left untreated (control). The plants were grown in a five part soil mixture for five weeks in a greenhouse; 10% of the mixture was a multispecies mycorrhizal inoculum consisting of cultures isolated from agricultural soils. Roots were cleared, stained, and evaluated for the extent of mycorrhizal root colonization. Plant biomass, height, growth stage, and tissue analysis were measured to evaluate differences between both crop varieties and seed treatments.
In oat varieties, there was no effect of fungicide on arbuscular colonization rate or on phosphorus concentration of the host relative to the control. The use of Raxil MD was found to result in a significantly lower (p≤0.05) arbuscular colonization rate compared to the use of Evergol Energy. Total colonization was also significantly different (p≤0.001) between the two oat varieties.
In soybean varieties, arbuscular colonization and phosphorus concentration remained unaffected by fungicide use. However, an interaction was observed between fungicide and variety for phosphorus and zinc concentration. With Davison soybean, both CruiserMaxx Advanced and Evergol Energy SB significantly increased (p≤0.05) P concentration relative to the control. With ‘Codington’, Zn concentration was significantly lower (p≤0.05) with the use of CruiserMaxx Advanced.
In corn, fungicides did not affect colonization or phosphorus concentration levels relative to the control. Cruiser Extreme was found to have a significantly lower (p≤0.05) arbuscular colonization rate and biomass relative to the use of Stamina and Trilex fungicides. Corn variety 60-01N had significantly lower arbuscular and total colonization rates (p≤0.05; p≤0.01) compared to the two other corn varieties.
Of the varieties and fungicides tested, there was largely no effect of fungicides on arbuscular colonization or host phosphorus status relative to the untreated control plants; some differences between the fungicides were observed that were variety specific for soybean. The findings suggest that seed applied fungicides on locally grown oat, soybean, and corn varieties have a minimal, if any, effect on arbuscular colonization and host phosphorus status that is largely influenced by host genotype.

Library of Congress Subject Headings

Vesicular-arbuscular mycorrhizas

Mycorrhizal fungi

Plant-fungus relationships

Symbiosis

Plants -- Effect of fungicides on

Oats -- Varieties -- South Dakota

Soybean -- Varieties -- South Dakota

Corn -- Varieties -- South Dakota

Description

Includes bibliographical references

Format

application/pdf

Number of Pages

151

Publisher

South Dakota State University

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Included in

Plant Biology Commons

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Rights Statement

In Copyright