Evaluation of the antagonistic effect of Trichoderma species on Phytophthora citrophthora, the causal agent of citrus root and crown rot

Crown and root rot is one of the important diseases of citrus trees in Iran. Various methods, including biological control, have been proposed to control this disease. Trichoderma species are widely present in all soils and plant materials. In this study, 27 Trichoderma strains were used for biological control of Phytophthora citrophthora. Measurement of cellulase enzyme and beta 1-3 glucanase produced by Trichoderma spp. was done using the dinitrosalicylic acid method. The results showed that the highest values are related to T. harzianum CT-763 and T. virens CT-9715 strains with 2 µmol/ml enzyme activity. Macroscopic and microscopic examinations of the dualculture of different Trichoderma strains with the pathogen, the inhibitory effect of volatile and non-volatile metabolites on mycelial growth of the pathogen were done. All Trichoderma strains and their volatile and non-volatile compounds inhibited on pathogen mycelia growth. The highest percentage of inhibition dualculture tests was caused by T. virens CT-9715. The highest inhibitory effect was determined for T. afroharzianum CT-891, T. aureoviridis CT-936, T. atroviride CT-865 with 100% and T. afroharzianum CT-55 with 50% in the non-volatile and volatile compounds assay, respectively. In microscopic examination of mycoparasitism effect of Trichoderma spp. and P. citrophthora, it was found that T. harzianum (CT-566, CT-862, CT-634, CT-873), T. afroharzianum CT-55 and T. aureoviridis CT-936, destroyed the mycelium of pathogen by a process such as twisting and lysis. For application of these successful local strains as biopesticide, it is necessary to perform additional studies on their biocontrol effects on Phytophthora in natural conditions.