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Title: Investigations on the Effect of Trichoderma Viride and Pseudomonas Fluorescens against Late Blight of Potato (Solanum Tuberosum) Under Greenhouse Conditions
???metadata.dc.contributor.*???: Dr. R. Amutha
Debebe, Ephrem
Issue Date: Jul-2005
Publisher: Addis Ababa University
Abstract: Late blight caused by the oomycete pathogen, Phytophthora infestans (Mont.) de Bary, is the most devastating disease of potatvj throughout the world including Ethiopia. The disease is usually controlled by lepeated applications of chemical fungicides. The serious pollution problems associated with the use of chemicals and the development of resistance to the available fungicides by new and more aggressive P. infestans strains urge us to have alternative control strategies such as biological control. Trichoderma viride-TNAU and Pseudomonas fluorescens-Bak150 were tested for their efficacy in controlling the pathogen in vitro and in greenhouse. In vitro antagonism test between T. viride and P. infestans showed a radial growth inhibition of the pathogen by 36.7% followed by a complete overgrowth of T. viride on P. infestans. P. fluorescens inhibited, the radial growth of the pathogen by 88%. Foliar spray method used in the greenhouse trial involved foliar spraying of the plants with suspensions of (1) T. viride, (2) P fluorescens, (3) mixed culture of the two antagonists and ;( 4) chemical, fungicide mancozeb followed by spraying the pathogen three days later. Percentage leaf area infection was measured every week and area ’under' the disease progress curve (AUDPC) was calculated and compared among the treatments. The result showed that T. viride (AUDPC=260) and P. fluorescens (AUDPC=765.1) significantly (P<0.05) reduced the disease compared to the untreated check (AUDPO=1045). T. viride was found to be more efficient than P. fluorescens and the mixed culture of the two. No significant difference was observed between the mixed culture and the inoculated/untreated check. On the other hand, seed treatment method of the greenhouse trial involved dipping artificially infected seed tubers in to the suspensions of the antagonists followed by planting the tubers. The result showed no significant difference (P>0.05) in the disease severity (AUDPC) among each of the treated ones and the inoculated/untreated controls. Thus, neither the bioagents nor the chemical fungicide was able to control or suppress the transmission of the pathogen from the infected tubers to the emerging sprouts and the subsequent progress of the disease.
Description: A Thesis Presented to the School of Graduate Studies of the Addis Ababa University in Partial Fulfillment of the Requirements for the Degree of Master of Science in Biology
Appears in Collections:Thesis - Biology

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