Selection of bacterial antagonists for the biological control of Botrytis cinerea in apple (Malus domestica) and in comparison with application of thiabendazole.

In this study fifteen strains of identified Pseudomonas fluorescens and Bacillus subtilis were investigated for biological control activity against Botrytis cinerea. P. fluorescens P-35 and B. subtilis B-16 showed the most inhibitory zone in dual culture assay against B. cinerea, In vitro. After ten days, P. fluorescens P-5 and B. subtilis B-3 showed the considerable results against B. cinerea on apple fruits and could reduce the grey mould from 100% to less than 35%. After twenty days, P. fluorescens P-5 and 8. subtilis B-16 decreased the disease from 100% to less than 65%. Also, application of thiabendazol at 1500 mg/litre was more effective and could reduce the disease from 100% to 30% and 60%, after 10 and 20 days respectively. Results indicated that there is no significant difference among the treatments (thiabendazol and bacterial strains). So, bacterial strains could not only control the disease but also be a reliable replacement instead of Thiabendazol.

Screening of Pseudomonas and Bacillus isolates for potential biocontrol of the damping-off of bean (Phaseolus coccineus).

In this study fifteen isolates of identified Pseudomonas fluorescens and Bacillus subtilis were investigated for control of bean damping-off disease caused by Rhizoctonia solani. In vitro, P. fluorescens P-6 and B. subtilis B-3 showed the most inhibitory zone in dual culture assay against R. solani. The growth of P-6 (4.5 x 10(8) cfu/ml) was significantly higher than in the other treatments. In greenhouse condition, all of the isolates effectively controlled damping-off on bean. P. fluorescens P-5 and P-6 showed the considerable results against R. solani and could reduce the damping-off disease from 100% to less than 30%. P-5, P-6 (P. fluorescens) and 8-16 (8. subtilis) strains had the highest effect on fresh weight of bean.

Effect of essential oils in control of plant diseases.

In this study, antifungal activity of some essential oils, extracted from Syzygium aromoticum, Foeniculum vulgare, Cuminum cyminum and Mentha piperita were investigated against grey mould of apple. The essential oils of S. aromaticum and F. vulgare showed considerable antifungal activities on PDA medium against Botrytis cinerea. Results indicated that the increasing of dosage of the essential oils caused to the more antifungal activity against B. cinerea in vitro condition. After 10 days, results showed that the essential oil of F. vulgare in both of the concentrations (750 and 1000 microL/L) was more effective than the essential oil of S. aromaticum against grey mould of apple and decrease the disease up to 15.5% in comparison with the check treatment (100%). After 20 days, biocontrol potential of the essential oils of S. aromaticum and F. vulgare at 1000 microL/L were more effective than the other treatments and the percentage of disease was evaluated 41.6% and 50.8%, respectively, in comparison with the check treatment (100%).