Control of blast disease caused by Pyricularia oryzae with Epicoccum nigrum and microscopic studies of their interaction with rice plants under greenhouse conditions

Abstract

Rice (Oryza sativa L.) feeds around half of humanity mainly in Asia, South America, and Africa. The filamentous, ascomycete fungus Pyricularia oryzae Cavara (syn: Magnaporthe oryzae B. Couch) hemibiotrophic phytopathogen is the causal agent of the most devastating disease, blast on rice. The fungus E. nigrum is ubiquitous resistant in adverse conditions and used as a biological control agent (BCA) against numerous phytopathogenic fungi in the function of its ability to produce many secondary metabolites. This study aimed to evaluate the efficiency of an isolate of E. nigrum on rice blast disease suppression, as well as rice growth promotion and productivity of the cultivar BRS.MG Caçula, in pot assay under greenhouse conditions, and evaluate the interaction between plants and microorganisms, using microscopic approaching. Rice leaf blast disease incidence and severity were evaluated on seeds and plants, which were treated with E. nigrum and P. oryzae isolate IA25, and compared with the control treatment. Foliar spraying and coating of the rice seed with E. nigrum significantly reduced the incidence rate of rice blast from 31.25% to 41.76%, respectively, compared to the control treatment. Likewise, the severity rate was reduced from 34.92% to 54.51%. In-plant growth, it was found that seed-soaking with Epicoccum provided plant fitness and increases the number of tillers to 8.34 against 5.95 for the control situation. The Epifluorescence Microscopy (EFM) and Scanning Electron Microscopy (SEM) showed the colonization of rice root by endophytic fungus E. nigrum. The greenhouse experiments confirmed that E. nigrum significantly decreased rice leaf blast disease incidence and severity rate while improving plant tillering.