Abstract

Rice blast disease caused by fungus Magnaporthe oryzae (syn. Pyricularia oryzae) is one of the most damaged diseases of rice reducing plant production worldwide. In the present study, Bacillus subtilis strain GB519 was identified from the rhizosphere based on predicted signatures of 16S rDNA and gyrA gene and morphological, biochemical and physiological characteristics. Treated with B. subtilis GB519, rice plant exhibited increased germination rate, vigor index, shoot length, shoot fresh weight, root fresh weight coupled with more production of Indole Acetic Acid (IAA), organic (Porg) and inorganic phosphorus (Phos). In culture GB519 inhibited growth of following rice fungal pathogens (in order from most effective to least effective): M. oryzae, Ustilaginoidea virens, Fusarium graminearum, F. moniliforme, F. oxysporum and Rhizoctonia solani. Three years studies showed that when rice was sprayed with GB519, there were significant reductions in rice blast incidence both in greenhouse and fields: 70.3% and 62.1% in 2017, and 69.9% and 71.6% in 2018, 75.1% and 75.6% in 2019. Such reductions were correlated with accumulated hydrolytic enzymes including amylases, proteases, chitinase and lipases, and the defense enzyme activity of the total antioxidant capacity (TAOC), catalase (CAT) and superoxide dismutase (SOD) in rice. Field experiments showed that the biocontrol efficacy of GB519 was similar to that of other biological and chemical fungicides. Our results that B. subtilis strain GB519 promoted plant growth and reduced blast disease suggest that this strain has potential to be used as a biological control agent against rice blast.