TITLE:
A Phytotoxic and Antifungal Metabolite (Pyrichalasin H) from a Fungus Infecting Brachiaria eruciformis (Signal Grass)
AUTHORS:
Kumudini M. Meepagala, Brandon M. Clausen, Robert D. Johnson, David E. Wedge, Stephen O. Duke
KEYWORDS:
Mycotoxin, Brachiaria eruciformis, Phytotoxicity, Pyricularia grisea, Pyrichalasin H
JOURNAL NAME:
Journal of Agricultural Chemistry and Environment,
Vol.8 No.3,
August
8,
2019
ABSTRACT: Brachiaria eruciformis (sm.) Griseb, locally known
as “signal grass”, is a common weed in lawns and turfs in Mississippi, USA. During late spring and early summer months, leaves
of B. eruciformis are infected with a
fungus causing necrosis. The infected leaves ultimately turn brown and wither.
As part of our search for potential new natural product-based agrochemicals, we
studied this plant pathogen in order to investigate phytotoxic and fungitoxic
metabolites produced by the fungus. The causative fungus was isolated from an infected
leaf of B. eruciformis, cultured in
potato dextrose agar plates and identified via molecular techniques as Pyricularia grisea. A phytotoxic compound was isolated from Czapek-Dox
broth liquid culture medium and identified as pyrichalasin H by spectroscopic
techniques. Pyrichalasin H was toxic to the fungal plant pathogen Colletotrichum fragariae in a TLC bioautography assay and phytotoxic to two monocot and one dicot plants. This
is the first report of antifungal activity of pyrichalasin H against
phytopathogens. Pyrichalasin H isolated from Pyricularia grisea, a pathogen infecting B. eruciformis (signal grass) was shown to
be phytotoxic and fungicidal to Colletotrichum fragariae.