بررسی فعالیت آنتاگونیستی جدایه های اندوفیت مرتبط با بذر دو گیاه دارویی بر قارچ بیمارگر Alternaria alternata، به روش کشت متقابل

Endophytic fungi are a group of host-associated fungal communities that colonize intercellular or intracellular spaces of host tissues without causing any symptoms. They produce bioactive metabolites that belong to different chemical classes and show diverse biological properties. Some of these metabolites have indicated antimicrobial effects. This study is an effort to screen the biological characteristic assay (antagonistic potential) of the seed-associated mycobiota community, including Colletotrichum gloeosporioides and Chaetomium globosum, isolated from medicinal plants Lycium barbarum L. and Eryngium caucasicum Trautv, respectively. The inhibitory potential of the endophytic fungal isolates was conducted against Alternaria alternata, the causal agent of black rot in Citrus fruit, by the cross-plate method. The activated endophytic isolate disk (with a diameter of about 0.5 cm) was inoculated on the PDA medium, and the pathogenic fungus disk was put 2 cm away from the center of the medium and incubated at 25◦C. On the other side, the endophytic isolate and the pathogenic fungus plates were equidistant from the edge of the petri dish, and the control (without antagonistic isolates) was used as the blank. Each treatment was repeated three times. After 7◦days, the fungal growth diameter was measured, and the fungistatic rate was determined using Abbott's formula. According to antagonistic efficiency results, both endophytic isolates showed more rapid growth on PDA than the pathogenic fungus under the same growth conditions. C. gloeosporioides isolate showed the highest inhibition rate of pathogen growth at 75.44%, and the fungistatic rate of C. globosum isolate was measured at 51.76%. The mean colony diameter (mm) of A. alternata ± standard error in three replications of each endophytic isolate was measured at 9.33 ± 3.38 b (mm) and 18.33 ± 5.89 b (mm), in C. gloeosporioides and C. globosum, respectively. The values with different lowercase letters indicate significant differences (P < 0.05) according to Tukey's test. The results acknowledge that the mycelial growth of the pathogenic fungus was suppressed substantially in the presence of both antagonists compared to the control sample. Moreover, these results confirm that the endophytic fungi within medicinal plants are potential sources of valuable bioactive compounds with antimicrobial activity. Future research should identify these fungal endophytes and their metabolite compounds and explore their usage as substitutes and complements for chemical fungicides.