comparison of sugar beet and sugar cane molasses regarding their influence on production and efficiency of pseudomonas fluorescens, the biocontrol agent of sclerotinia sclerotiorum

the most common pathogenic agent in sunflower is sclerotinia sclerotiorum which in some cases can be successfully controlled by some antagonistic bacteria. environmental factors such as carbon sources are effective on antagonistic strains but application of pure carbohydrates for mass production of these agents is expensive. so in most cases agricultural and industrial residues (such as molasses) which are rich of such carbohydrates are used. in this research, the strain utpf61 was selected out of 47 strains of pseudomonas fluorescens. then, the effect of two media containing sugar beet molasses and sugar cane molasses on growth, antagonistic efficacy (in vitro), and antifungal activity of the bacterium on sunflower in greenhouse was investigated. results showed that there was no significant difference between the two media in terms of growth and antagonistic efficacy of the bacterium in both environmental but they were significantly different from the control treatment. the two media were effective on antagonistic efficiency in greenhouse trials (with 80% and 78% protection against the fungus, respectively). investigation of sunflower growth paramters in greenhouse trials indicated that sugar beet molasses increased dry weight of sunflower, but no significant difference was observed between these two media for the length of stem, length of root and fresh weight of plant.