Exploring fungal endophytes as biocontrol agents against rice blast disease

The rice blast disease caused by Pyricularia oryzae Cavara is among the most severe plant diseases in the world. The utilization of natural antagonists, such as fungal endophytes, can be a good method to control the spread of this disease. In the present study, 68 fungal isolates were obtained from 160 rice samples collected in Guilan province fields, Iran. Morphological and molecular characteristics were used for the identification of these fungi. According to the results, the fungal isolates were Alternaria citri (Penz.) Mussat, Alternaria infectoria Simmons, Aspergillus fumigatus Fresen, Fusarium verticillioides (Sacc.) Nirenberg, Trichoderma harzianum Rifai, Trichoderma virens (Mill., Giddens & Foster) Arx, Trichoderma viride Pers., Ulocladium consortiale (Thum) Simmons, and Pyricularia oryzae . Eight isolates that did not cause any plant disease were selected for biocontrol studies in vitro . The dual culture, culture filtrate, slide culture, and volatile metabolites methods were used in search of natural endophytic antagonists of Pyricularia oryzae. It was found that T. harzianum, T. virens, T. viride, A. fumigatus, and A. citri isolates caused the highest percentage of mycelial growth inhibition of P. oryzae in vitro. In the greenhouse experiments, all of the studied isolates reduced the P. oryzae disease rating, with T. harzianum isolate being the most effective antagonist (27.36% reduction in the disease rating), followed by T. virens, T. viride, and A. fumigatus (20.75%, 17.92%, and 16.98%, respectively). Furthermore, in greenhouse conditions, these antagonistic fungi increased the height, fresh weight, and dry weight of plants. The results of this research showed that there are various fungi in the natural flora of rice plants that possess potential biological properties against rice blast disease that can be implemented into practice.