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.
Highlights
IntroductionPhytopathogenic fungi use the host plant as a source of nutrients for its growth and development
Microbes are good sources of bioactive compounds [1]
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
Summary
Phytopathogenic fungi use the host plant as a source of nutrients for its growth and development. In this process, the fungi often produce toxins that are lethal to the host plant and often toxic to other plant species, and these toxins may have insecticidal, antibacterial and antifungal activities as a result of coevolution and competition among species to survive in the biosphere [2] [3] [4]. Natural products offer broad chemical diversity with a wide range of bioactivities, including phytotoxicity. These compounds may have varying and multiple molecular target sites and can be used as novel compounds or templates for development of pest control agents [8]. This study focused on isolation of bioactive compounds from a pathogenic fungus infecting B. eruciformis (signal grass)
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