Document Type

Thesis - Open Access

Award Date

2019

Degree Name

Master of Science (MS)

Department

Agronomy, Horticulture, and Plant Science

First Advisor

Emmanuel Byamukama

Second Advisor

Bruce Bleakley

Keywords

bacteria leaf streak, epiphytes, seeds, wheat, Xanthomonas translucens pv undulosa

Abstract

Wheat (Triticum aestivum) is the most important staple food for over two billion people, or 36% of the world population. The United States ranks 4th in the world for wheat production. However, wheat production is faced by both biological and non-biological constraints. Among the biological constraints, diseases play a big role in limiting wheat production with estimated yield losses ranging from 20% to 40%. Bacterial leaf streak (BLS) of wheat caused by Xanthomonas translucens pv undulosa (Xtpvu) is one of the major bacterial diseases affecting the wheat production in most wheat growing regions in the USA. In recent years, it has become more prevalent in the upper mid-west due to the warm and humid summer conditions that highly favor its development. In our study, we looked at various synthetic products and bio-pesticides and tested their efficacy in managing BLS in both greenhouse and in the field. We also determined how the epiphytic bacteria diversity is influenced by environment and cultivar. Lastly, we determined the effects of various spices and plant extracts on the growth of Xtpvu invitro. In the greenhouse study, we applied synthetic and biopesticide products that included: Champ 2, Regalia, Badge SC, Cuproxat® FL, Sonata ® ASO, Biochar and Headline on wheat (Brick). Plants were later inoculated and rated for disease severity by measuring the percentage of the leaf area affected with disease. Under field conditions, we conducted the experiments at the North Research Farm (NERF) and Volga Research Farm with the same products that we used in the greenhouse study with plant extracts, and other synthetic chemicals. The wheat variety Select was used in the field due to its high susceptibility to BLS. The experiment was laid in a completely randomized block design with four replicates. We randomly picked 10 plants per plot and determined the percentage of leaf area affected by the disease. There was no significant difference among treatments in comparison to the check for the greenhouse study. For the field study, there were significant differences among the synthetic and biopesticides with Sonata ASO and Cuproxat having relatively low disease severity with mean log transformed percentage severities of 1.27 and 1.25 respectively. There were no significant differences in effects among the plant extracts when compared to the check in the field study. Yield and test weight were not significantly different among treatments. The most abundant genera identified on seeds were: Sphingomonas, Pseudomonas, Pedobcater, Neorrhizobium, Microbacterium, Methylobacterium, Massilia, Hymenobacter, Kinecoccus, Muciliginabacter, Curtobacterium, and Chrysobacterium. Sphingomonas had a higher relative abundance compared to other genera in both locations while the genera that could harbor potential wheat pathogens were Pseudomonas and Xanthomonas. Among all the plant extracts and spices tested, only tannic acid had possible bactericidal effects. This study demonstrates that some ethyl acetate extracts of plant products have a significant antimicrobial effect on Xtpvu in vitro. Further research is needed to test plant extracts and spices in the field for potential integration into bacterial leaf streak management in conjunction with the current bacterial leaf streak management practices.

Format

application/pdf

Number of Pages

108

Publisher

South Dakota State University

Rights

In Copyright - Educational Use Permitted
http://rightsstatements.org/vocab/InC-EDU/1.0/

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