The Ability of Some Trichoderma Isolates and Epiphytic Bacteria In growth inhibition of the wheat septoriosis agent

Background and Objective

Septoriosis is one of the important diseases of wheat in the world and Iran too. Considering the high cultivated area of wheat and the economic importance of this crop in Ilam province, the present study done with the aim of investigating the combined effects of Trichoderma fungus and epiphyte bacteria to reduce the damage caused by Septoria tritici on two Mehregan and Tajan varieties of wheat in vitro and under greenhouse conditions.

Materials and Methodes

The inhibition ability of 12 isolates of Trichoderma isolates was evaluated in vitro by duel culture and production of volatile metabolites. In addition, the inhibition effect of 207 epiphyte bacteria strains obtained from wheat leaves was examined with three tests including; antibiotic, volatile metabolite and siderophore production.

Preparation of Trichoderma inoculum was done according to the method of Stocco et al. (2016). Fungal suspension was prepared and the concentration of spores in the resulting suspension was determined using a hemocytometer slide, 1 x 108 conidia per ml for each Trichoderma isolate. Then, ten milliliters of the suspension prepared from each isolate was mixed with 90 milliliters of 0.25% agar water.The seeds of Tajen and Mehrgan cultivars were added to the above suspension. The seeds coated with Trichoderma were dried in the dark at room temperature and after 24 hours, they were planted in 2 kg sterile pots. 5-7 seeds were used in each pot.

In order to prepare the inoculum of epiphyte bacteria, 24-hour culture of bacteria on NA culture medium was used and a suspension of bacteria was prepared in sterile distilled water and optical absorption of 0.1 at wavelength of 600 nm was done using a spectrophotometer. Inoculation of the bacterial inoculum was done using a manual spore sprayer and 24 hours before the inoculation of the pathogenic fungus.

After preparing the pathogenic fungus spore suspension, two-leaf seedlings (14 days old) were inoculated. The pots were covered with plastic bags for 72 hours and kept in the dark for 24 hours. During this period, the environment of the pots was kept moist by using a hand sprinkler. After the mentioned period, the plastic bags were removed from the surface of the pots and kept for another 21 days at a temperature of 23 degrees Celsius and in a humidity condition higher than 70%.

Under greenhouse conditions, growth characteristics of wheat including; fresh and dry weight root (g), fresh and dry weight shoot (g) and plant height (cm) were evaluated in the presence of pathogenic fungus and biocontrol agents. The data analysis ANOVA (Analysis of variance) was conducted using of the SAS software version 9.6 as a factorial test in completely randomized design (CRD) with three replicates.

Results

The results showed two fungal isolates T6 (T. Longibrachiatum) and T1 (T. harzianum) and three bacterial strains C1d (S. saprophyticus), Dr1b (P. agglomerans), B2b (E. cloacae) had the ability to inhibit of the growth of S. tritici in vitro, which the mentioned isolates were selected for the greenhouse test.

The greenhouse results showed the strong effect of combined treatment of fungus-bacterial T6+C1d (T. longibrachiatum+S saprophyticus) in increasing all functional traits of wheat and T1+B2b treatment (T. harzianum+E. cloacae ) had the lowest effect on plant functional traits.

The t-test results between Mehregan and Tajan cultivars showed the highest fresh and dry weight root, fresh and dry weight shoot and plant height were obtained for Tajen variety. Generally the results showed the positive effect of various fungal and bacterial isolates in reducing the pathogenicity and damage caused by the septoriosis disease.

Discussion

The results of antagonistic ability of fungal isolates and epiphytic bacteria in vitro and greenhouse showed there is a good correlation between two conditions. So the results showed a positive effect of the fungal and bacteria isolates in reducing Septoria damages. Finally, isolates T6 (T. Longibrachiatum) and T1 (T. harzianum) and three bacterial strains C1d (S. saprophyticus), Dr1b (P. agglomerans), B2b (E. cloacae) were intreroduced as the strongest antagonistic agents in control of this fungus. The possible main effects of T. longibrachiatum is related to induced resistance in the plant and the produce of volatile metabolites and antibiotics, and in bacteria are related to produce of volatile metebolites, antibiotics and siderophore.