BIOLOGICAL CONTROL OF Phoma lingam, THE CAUSAL AGENT OF RAPESEED BLACKLEG, BY Trichoderma AND Bacillus subtilis ISOLATES

Many isolates of Trichoderma spp. and Bacillus subtilis are natural biological agents of plant pathogenic fungi and bacteria. Trichoderma spp. and B. subtilis isolates were separated from the rhizosphere of infected and non-infected rapeseed plants. Phoma lingam, the causal agent of rapeseed black leg, was isolated from different tissues of infected plants, and infested soil. Dual cultures were used to examine the antagonistic effects of Trichoderma and B. subtilis isolates on P. lingam. In the greenhouse, the antagonistic effects of the isolates were tested through treating rapeseed seeds and rapeseed above-ground parts with the isolates. Totally, 20 isolates of P. lingam, 15 isolates of Trichoderma species and 17 isolates of B. subtilis were separated. Bacterial isolates BE3, B31, B66, B67, B68, B69, and B70, and Trichoderma isolates Tr.2901, Tr.2903, Tr.2904, Tr.2910, and Tr.2913 showed antagonistic effects on the pathogen. The greenhouse results revealed that in the seed treatment experiment, the bacterial isolates B70 and B67, and Trichoderma isolates Tr.2910 and Tr.2901 decreased the rapeseed blackleg to 43.3, 80, 16.6 and 56.6℅, respectively. Treating the above-ground parts with bacterial isolates did not reduce rapeseed blackleg at all. Treating above-ground parts by Tr.2910 and Tr.2901 isolates of Trichoderma decreased the disease to 60 and 79.6℅, respectively. Trichoderma isolates belonged to several species where the differentiation of the isolates from species was impossible based on the morphological characteristics. The two effective bacterial isolates were related to B. subtilis.