Abstract:A biocontrol fungus FJAT-9040 identified as Trichoderma harzianum, was found to have high inhibition on mycelial growth of Fusarium oxysporum isolated from solanaceous crops. In order to visualize survivability and colonization of this biocontrol fungus in soils, green fluorescence protein gene (gfp) was transformed into the strain FJAT-9040 using protoplast-mediated genetic transformation. A transformant, FJAT-9295, with strong and stable expression of the fluorescent protein was chosen to compare their biological characteristics with the wild type strain FJAT-9040. There were no significant differences between the transformant and the wild type strains in growth rate, spore yield, adaptability to culture pH or temperatures and antifungal activity (P>0.05). The transformant FJAT-9295 was then used to visualize its colonization in four types of soils and the effects of plants on its colonization. Among the four types of soils, the best soil for colonization of the strain FJAT-9295 was nursery soil, the garden soil and sandy soil ranked second, and the last one was loess soil. The population of strain FJAT-9295 in the eggplant-grown soils was higher than that in the non-crop control soils. After mixed with soils, the population of strain FJAT-9295 decreased gradually compared with the initial inoculum in different types of soils; however, they were stabilized with approximately 105 CFU/g after 16 days in the soils.