Biological control of rice blast disease by antagonistic fungi in vitro and under greenhouse conditions

The rice blast disease caused by Pyricularia oryzae is one of the most important fungal diseases in Iran and worldwide. From 150 samples of healthy and infected rice seedlings, leaves and spikes collected from paddy fields of Guilan province, 68 fungal isolates were obtained. Eleven isolates identified based on morphological and molecular methods that were not able to cause disease on rice in pathogenicity test including Ulocladium alternariae, Ulocladium cf. alternariae, Ulocladium cf. consortiale, Ulocladium sp., Curvularia pallescens, Preussia sp., Trichoderma harzianum, Trichoderma virens, Trichoderma viride, Alternaria citriand Epicoccum sp. were selected for rice blast disease biocontrol studies. In the laboratory, we useddual culture, culture filtrate, slide culture and volatile metabolites methods and based on results, T. harzianum, T. virens, T. viride, A. citri and U. cf. consortialeisolates had highest percentage of mycelial growth inhibition of P. oryzae. These fungal isolates were inoculated in a four–leaf stage on rice plant of Hashemi cultivar under greenhouse conditions. All inoculated fungi except U. cf. alternariae, reduced leaf blast disease rating, among them T. harzianum with 27.36% reduction in disease rating was the most effective antagonist in greenhouse studies followed by T. virens, T. viride and A. citri. Comparison of data average in least significant difference (LSD) method showed that there was significant difference betweenbiocontrol fungi (T. harzianum, U. cf. alternariae and Preussia sp.)in terms of efficiency in rice blast control. Also, there was a statistically significant difference between the fungi in terms of effect on height, fresh weight and dry weight of rice plants in the greenhouse andamong these fungi, T. harzianum showed the highest efficiency in improving these traits.The results of the present study showed that there are different fungi in microflora of rice plants which are considered as potential biological control of rice blast disease.