Alemu, Tesfaye (PhD)Hadush, Goitoom2020-11-272023-11-092020-11-272023-11-092019-10-10http://etd.aau.edu.et/handle/123456789/23650Biological control with microbial antagonists is considered an alternative approach for controlling plant diseases. Trichoderma species are one of the potential fungal biocontrol agents in suppression of soil-borne and foliar pathogens. The present study aimed to evaluate, test and characterize potential biocontrol agents of Trichoderma isolates against two pathogenic isolates of Colletotrichum species under in vitro condition. Infected sorghum leaf, sheath, stalk and soil samples were collected from different ecological habitat of Welkait district for the isolation of Colletotrichum isolates. The study examined the effect of pH and temperature on the mycelia growth and spore yield of Trichoderma isolates in broth culture. In this study, the in vitro potential of 7 Trichoderma isolates were evaluated against two pathogenic Colletotrichum isolates in dual culture techniques and through production of volatile and non-volatile inhibitors. Pathogenicity test was confirmed Colletotrichum isolates as one of the fungal organisms responsible for sorghum anthracnose disease. It was observed that the optimum pH and temperature for maximum mycelial growth and spore yield produced by Trichoderma isolates in broth cultures was pH 7.5 and 25OC, respectively. In vitro screening results showed that the proportion of isolates with antagonistic activities was the highest for the AUC-1 isolate followed by AUC-2 isolate. In vitro confrontation analysis revealed that all Trichoderma isolates were highly antagonistic against AUC-1 whereas AUT-97, AUT-131, AUT-11 and AUT-12 isolates displayed over 75% inhibition of mycelial growth of AUC-2 isolate (P<0.05). The isolates AUT-11 and AUT-12 showed consistent results in volatile and non-volatile activity under in vitro condition against any of the two pathogen isolates tested. Under in-vitro dual culture test, all isolates of Trichoderma were able to inhibit the growth of both Colletotrichum isolates at rates ranging from 58.92% to 90.29% after 8 days of incubation. The highest mean inhibitory effect on the growth of the test pathogens were achieved by AUT-11 isolate (90.29%) against AUC-1 and AUT-97 isolate (81.1%) against AUC-2 while AUT-32 isolate showed the lowest mean inhibitory effect restricting it almost completely in plates as compared to the control consisting of any of the two test pathogens growing alone. In dual culture, volatile and nonvolatile tests, all the Trichoderma isolates significantly inhibited the radial growth of the two Colletotrichum isolates at (P<0.05) compared with control. Thus, the use of novel isolates of Trichoderma with efficient antagonistic capacity against Colletotrichum isolates is a promising alternative strategy to pesticides for sorghum anthracnose disease management.enAntagonismColletotrichumDual CultureInhibitionTrichodermaThesis