Document Type

Dissertation - Open Access

Award Date

2020

Degree Name

Doctor of Philosophy (PhD)

Department / School

Biology and Microbiology

First Advisor

Heike Bucking

Keywords

beneficial plant microbe, corn, plant growth promotion, soybean, wheat

Abstract

Bacterial endophytes have the capability to enhance plant growth by producing plant growth hormones, solubilizing phosphates, suppressing pathogenic fungi, and reducing plant stress hormones. These capabilities make them desirable limiting the amount of nutrients and pesticides that are applied to crops. Through these assays and isolations, it is possible to identify novel bacterial species. In-vitro testing had shown 9 of the 20 isolates possess the ability to produce indole-3-acetic acid (IAA) with Pantoea agglomerans BC09 producing a concentration of 30.2 ng/μl over 4 days. BC09, Bacillus subilis BC10, and Pantoea sp. BC12 were able to solubilize calcium phosphate, 7 endophytes exhibited amplification of the 1-aminocyclopropane-1-carboxylate deaminase (ACC deaminase) gene (acdS), and the plant pathogen Fusarium proliferatum had shown suppression from 17 endophytes. In-planta studies with wheat show differences between spring wheat genotypes, with BC12 and Bacillus cereus BC14 increasing Boost’s root volume more than 80% and Enterobacter sp. BC05 increasing root volume of Prevail 87%. The corn genotype 5126RR was significantly increased 72% in root volume with Bacillus pumilis BC07 applications. Brookings soybean variety increased most across endophyte applications with BC07 increasing seedling mass and root volume more than 71%. Greenhouse trial responses did not always respond to the same endophytes as root architecture with Bacilus thuringiensis BC15 drastically increasing root dry biomass of Boost 102% under low nitrogen conditions and Prevail showing a significant increase in shoot under low or high nitrogen from 9 endophytes. Corn genotype 9714/G root and shoot biomass responded positively to Bacillus safensis BC16 inoculation under high nitrogen conditions. Codington soybean genotype significantly increased root biomass 23% after BC15 inoculation. When testing endophytes ability to increase yields under field conditions, all 3 crop species did not show a significant increase. Concentration of nitrogen in plant tissue was similar to controls for both soybean and corn while phosphorus concentrations only differed in Codington at R3 after Bacillus sp. BC20 applications. Additionally, isolation of endophytes leads to previously unsequenced and uncharacterized novel bacteria belonging to Methylorubrum under the proposed species M. endophytica.

Library of Congress Subject Headings

Brassica.
Endophytes.
Growth (Plants)
Plant nutrients.

Format

application/pdf

Number of Pages

174

Publisher

South Dakota State University

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Rights Statement

In Copyright