Theses and Dissertations

Issuing Body

Mississippi State University

Advisor

Maria Tomaso-Peterson

Committee Member

Hamed K. Abbas

Committee Member

W. Thomas Shier

Date of Degree

8-6-2021

Original embargo terms

Visible to MSU only for 1 year

Document Type

Graduate Thesis - Campus Access Only

Major

Agricultural Life Sciences (Plant Pathology)

Degree Name

Master of Science

College

College of Agriculture and Life Sciences

Department

Department of Biochemistry, Molecular Biology, Entomology and Plant Pathology

Abstract

The fungus Macrophomina phaseolina (Tassi) Goidanich (Mp) is the causal agent of charcoal rot in soybean and infects over 500 plant species worldwide. Mp produces various mycotoxins and is suspected of utilizing a toxin-mediated process to penetrate host tissue. Identification and evaluation of secondary metabolites produced by Mp will further elucidate the pathogenesis mechanisms used by the fungus. Mp cultures isolated from soybean were evaluated for phytotoxicity in a hydroponic soybean bioassay and chemically analyzed by LC-MS/MS. All Mp cultures at two dilutions induced phytotoxicity symptoms including chlorosis, necrosis, wilting, stunting, and death. Analysis identified 13 unreported secondary metabolites including mellein, a compound with various biological activities. The phytotoxicity of mellein was evaluated against soybean seedlings in hydroponic culture, and symptoms of wilting and stunting were observed at levels above 40 MUg/L. Observations suggest that mellein does not directly contribute to the phytotoxic effects of Mp cultures.

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