ارزيابي توانايي باكتريهاي اپيفيت در كاهش بلايت سنبله و پايداري جمعيت آنتاگونيست روي گندم در شرايط گلخانه اي

EVALUATION OF EPIPHYTIC BACTERIA FOR BIOCONTROL OF HEAD BLIGHT AND MONITORING STABILITY OF ANTAGONIST POPULATION ON WHEAT IN GREENHOUSE

To control Fusarium graminearum , the causal agent of wheat head blight, 350 strains of epiphytic bacteria were recovered and purified from wheat canopy. Based on the results of antagonistic properties of the collected strains, four strains including a nalidixic acid and chloramphenicol resistant mutant were selected and their potential for controlling head blight on falat wheat cultivar was evaluated in greenhouse. The plants at anthesis sprayed with antagonists (109 cfu/ml) and 24h later they were inoculated with macroconidium suspension (2x 1Q6 spoces/ml) of the pathogen. One week after inoculation, the heads monitored and diseases symptoms recorded. The analysis of variance showed significant deference between all treatments (P =99%). The mean comparisons by Duncan test showed significant differences in disease severity between pathogen plus antagonist treatments and positive control (only pathogen). No significant differences were observed among five antagonists in their biological ability. These five antagonists reduced the disease severity by 50-80% in comparisons with positive control. Tracing the marked antagonist (strain G5-2) showed that it maintained its population as much as 22- 56% of total resident bacterial population up to the harvesting time. This finding is considered a first reporting of tracing antagonist population on the host, which could be used as a tool of measuring antagonist population maintenance