Degree Type

Thesis

Date of Award

2016

Degree Name

Master of Science

Department

Agronomy

Major

Genetics and Genomics

First Advisor

Madan K. Bhattacharyya

Abstract

xSudden death syndrome (SDS) is one of the leading soybean diseases in the United States. The disease is caused by a soil-borne fungi Fusarium virguliforme in North America and by four Fusarium species, F. virguliforme, F. tucumaniae F. brasiliense and F. crassitipitatum, in South America. F. virguliforme infects the roots of soybean plants and releases toxins which causes the interveinal chlorosis and necrosis on leaves, premature defoliation, and flower and pod abortion that are typical foliar SDS symptoms. Yield losses associated with SDS can be economically devastating depending on disease intensity and timing of disease onset. Host-induced gene silencing (HIGS) has been shown to be an effective way to silence genes in a variety of species including barley, tomato, and western corn rootworm. In this study we designed a microfluidic device to observe the germination and sporulation of F. virguliforme. We observed that under the conditions used, the conidial spores of F. virguliforme take an average of five hours to germinate. The first conidial spores are being matured on average 64 to 69 h following suspension of spores in liquid media. It takes an average of 10.5 h for a conidial spore to mature and get detached from its conidiophore. Our microfluidic device enabled quantitative time-lapse microscopic-photography should be suitable for screening compounds, peptides, micro-organisms to identify fungitoxic or antimicrobial agents for controlling serious plant pathogens. We have also created transgenic soybeans expressing dsRNA targeting F. virguliforme genes believed to be important for housekeeping and virulence functions. In preliminary root-inoculation assays we observed that under low inoculum level, transgenic soybeans plants carrying the synthetic genes showed enhanced SDS resistance; whereas, under increased F. virguliforme inoculum level, they failed to show any resistance to the pathogen.

Copyright Owner

Jill Marshall

Language

en

File Format

application/pdf

File Size

86 pages

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