Antagonism capability in vitro of Trichoderma harzianum against some pathogenic fungi

摘要

The aim of this study is to clarify the antagonism capability in vitro of the antagonistic fungus (Trichoderma harzianum) against the pathogenic fungus, four isolates of pathogenic fungus associated internally with the solid wheat seeds ( Triticum durum )Desf , follower for species: Botrytis cinerea, Cladosporium sp, Stemphylium botryosum and Alternaria sp, were brought. The antagonistic sample (Trichoderma harzianum) was isolated from the wheat plant soil. The results showed that:The direct confrontation of Trichoderma harzianum against the different fungus isolates in vitro on PDA medium, showed in the third day of the experiment an inhibition in the pathogenic mycelia growth, with a different ratios, it was equal to: 41.66% and 50% for Stemphylium botryosum and Cladosporium sp, respectively, and amounted in the fourth day to 56.52% and 57.14% , for Botrytis cinerea and Alternaria sp, respectively, did not show any growth of the different pathogenic fungi when re-planting a disk from the interaction hyphal areas between the antagonistic fungus and the pathogenic fungus from the different dual cultures, while the antagonistic fungus was grown. The microscopic observations of the different interactions hyphal showed that the antagonistic fungus was affected on the pathogenic fungi with a several biological forms: Decomposition phenomenon (Lyses): the antagonistic fungus was analyzed the mycelia and spores of Cladosporium sp, while was analyzed the mycelia and damped the spore formation in the other pathogenic fungi, compared with control. Parasitism phenomenon (Mycoparasitism): it was found that the hyphae of Trichoderma harzianum has formed Haustoria on the cell walls of Stemphylium botryosum hyphae and they penetrated within them. The remote confrontation showed that the volatile metabolic substances of the antagonistic fungus affected the growth of the pathogenic fungi , with a different rates over the seven days of treatment, it peaked after two days of treatment to reach 13.33% and 50% in Botrytis cinirea and Cladosporium sp, respectively, and decreased to 08.33% in the fourth day in Botrytis cinirea and scored in the fifth day a ratio equal to 25.42% for Cladosporium sp, and was scored the maximum ratio in the third day in Stemphylium botryosum to 23.07%,and lowered to 07.93% in the seventh day, but in the Alternararia sp has recorded the lowest inhibition percentage to 05.55% in the third day and 05.76% in the seventh day. The microscopic observations Noted that the volatile metabolic substances of the antagonistic fungus was affected the pathogenic fungi with a several modes, their were with the mycelia analysis and prevent the spore formation in the Alternararia sp, while was analyzed and aggregated the spores in the Cladosporium sp, and stopped only the spore formation in both Botrytis cinirea and Stemphylium botryosum, compared with control.