Characterization and Pathogenicity of Blast Pathogen (Pyricularia grisea of Wild Finger Millet (Eleusine Africana and its Control Using Biological Antagonists and Fungicides
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Date
2017-02
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Addis Ababa Universty
Abstract
Blast (Pyricularia grisea) is an important disease of wild finger millet (Eleusine africana). It
causes disease on a wide variety of alternative hosts including agriculturally important plants
such as finger millet (E. coracana) in Ethiopia. A total of twenty six isolates of P. grisea were
isolated from infected wild finger millet plants from 5 different zones of Ethiopia. From the
initial twenty six isolates, only nine isolates were selected for the detailed morphological,
cultural, physiological and biochemical characterization based on their geographical location
and isolate type, whether it is isolated from stem, leaf, neck or seed parts. Among the different
media used host seed extract + 2% sucrose agar and oatmeal agar were found to be the best for
mycelial growth and sporulation of the isolates, dextrose was the most preferred among the
carbon sources and NaNo3 proved to be the best source of nitrogen for all the isolates. The
shape, color and compactness of the fungal colonies varied with the media used. At pH 6.5 all
the isolates exhibited maximum mean dry mycelial weight, and found optimum pH. The optimum
temperature range for the maximum growth of the isolates of P. grisea was found to be 20°C to
30°C. All the six P. grisea studied under green house for their pathogenicity, were able to infect
all the tested varieties. Among an In vitro evaluated fungicide against the test pathogen, both
Curzate and Sancozeb fungicides showed varied levels of antifungal activity and the highest
concentration (800 and 1000ppm) of fungicides were found of inhibiting the growth of the
isolates of P. grisea. With regard to the efficacy of the fungicides, Sancozeb was found to be the
most effective to inhibit the isolates. Among in vitro tested biocontrol agents viz. Trichoderma
viride, Trichoderma harzianum and Pseudomonas fluorescence, the growth of Trichoderma
species was fast, the clear inhibition zones were not formed in all incubated Petri plates,
therefore it was more effective than the bacterial antagonist. Compatibility of the biocontrol
agents with different fungicides (Curzate and Sancozeb) that is., Trichoderma harzianum and
Trichoderma viride in an in vitro condition resulted in that, both Curzate and Sancozeb, in lower
concentrations (100, 200, and 400ppm) were found well tolerated with both Trichoderma species
and hence they were shown effective in managing plant pathogens. Combining antagonists with
synthetic chemicals eliminates the chance of resistance development and reduces the fungicide
application.
Keywords: Finger millet, Pyricularia grisea, biocontrol, fungicide, compatibility, pathogenicity
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Keywords
Finger millet, Pyricularia grisea, Biocontrol, Fungicide, Compatibility, Pathogenicity