Document Type

Dissertation - Open Access

Award Date

2019

Degree Name

Doctor of Philosophy (PhD)

Department / School

Biology and Microbiology

First Advisor

Heike Bücking

Keywords

Arbuscular Mycorrhizal Fungi, Bacterial Endophytes, Disease Resistance, Wheat

Abstract

Arbuscular mycorrhiza, a symbiosis between plants and fungi, help plants to capture nutrients such as phosphorus (P), nitrogen (N) and other micronutrients from the aggre in exchange for up to 20% of the fixed carbon (C) from the plant. In addition, arbuscular mycorrhizal (AM) fungi can improve the resistance against abiotic (drought, salinity), and also biotic (pathogen) stresses. Bacterial endophytes promote plant growth and yield by fixing N2 from the atmosphere, assimilating N and transfer it to the plant. Bacterial endophytes can also solubilize phosphate and stimulate plant defense responses, suppressing pathogens. The host plant provides sucrose and a favorable place to live for the symbionts. Common root rot and foot or crown rot diseases are among the most common and destructive root diseases of wheat in South Dakota and represent a threat to yield productivity in every growing season. The goal of these studies was to examine whether AM fungi and bacterial endophytes can increase resistance of the plant against common root pathogens Bipolaris sorokiniana, and Fusarium acuminatum. We conducted greenhouse experiments to evaluate plant and seed biomass, seed count, root colonization with AM fungi, along with disease symptoms using two wheat cultivars. Our findings show that root colonization by AM fungi and bacterial endophytes can cause positive growth responses in the shoot and root at early time points and the plants don’t show a yield decrease after pathogen inoculation. The current management practices against common root and crown rot include rotation with broadleaf crops, seed treatment with fungicides and use of resistant seed cultivars. This research explores some of the many effects of AM fungi and bacterial endophytes on resistance to wheat root pathogens in the symbiotic relationship between fungi, bacteria and the host plant. Early application of AM fungi and bacterial endophytes can have a positive effect on wheat yield, reduce the addition of pesticides to the environment, assist cultivars in resistance to fungal diseases, and are a source of nutrients and growth stimulants for plants.

Library of Congress Subject Headings

Wheat -- Disease and pest resistance.
Roots (Botany) -- Diseases and pests.
Vesicular-arbuscular mycorrhizas.
Endophytes.
Plant-fungus relationships.

Format

application/pdf

Number of Pages

170

Publisher

South Dakota State University

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Rights Statement

In Copyright