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Biological Control of Some Soil-borne Fungal Pathogens of Soybean (Glycine Max (L.) Merr.) with Gliocladium spp.
Dissertation Abstract:
A study was conducted to screen isolates of Gliocladium spp. as biocontrol agents for soybean soil-borne pathogens, determine the proper substrate for mass production, and develop through greenhouse tests the effective technique in using promising isolates. Five isolates of Gliocladium spp. were taken from different places in the Philippines and isolated from soil mixed with decomposing material, cogon grass, litter, or rice straw mushroom spawn.
Tentative identification showed that the G. isolates were G. deliquescens and G. fimbriatum. They differed in color and morphology of sporulation, especially the phialides. Both species exhibited faster and better growth and sporulation on potato dextrose agar (PDA) than on Czapek agar or malt extract agar (MEA) medium. For optimum growth and sporulation, temperature range of 25-30°C, pH 5 and 6, and soil moisture content of 20-30 percent were needed. In vitro antagonsim tests on PDA showed that all Gliocladium isolates have antagonistic effect on Phythium aphanidermatum, Rhizoctonia solani, Scelrotium rolfsii, and Fusarium oxysporum.
For mass production of the biocontrol agent, Leucaena leaflets + coirdust, and Leucaena leaflets + sawdust proved to be the best substrates.
Among the four techniques of antagonist application studied, the best method developed and subsequently used was the one whereby Gliocladium in substrates was mixed with sterilized soil, added to the hole where the soybean seed was to be planted and incubated for seven days before seeding. The technique gave percentages of control P. aphanidermatum, R. solani, and S. rolfsii up to 90 percent, 88.4 percent, and 85 percent from infected seed and seedlings, respectively.
The series of studies showed that Gliocladium spp. had high potentials in controlling P. aphanidermatum, R. solani, and S. rolfsii in soybean, thus confirming earlier reports of their potential as biological control agents for soil-borne plant diseases. However, integrated pest management with other control techniques were recommended.
