Potential of Endophytic Fungi of Barnyard Grass Weed for Biological Control of the Rice Sheath Blight Pathogen, Rhizoctonia solani Kühn

Abstract

Endophytic fungi are group of microorganisms that colonize internal tissues of plants but do not cause any harm to their hosts. Although it has been reported that endophytic fungi from weeds have the potential as biological control agents against disease-causing pathogens of crops, the efficacy of those from barnyard grass weeds against sheath blight disease of rice caused by Rhizoctonia solani Kuhn has not yet been studied. This study determined the potential of endophytic fungi of barnyard grass weed (Echinochloa glabrescens Munro ex Hook. f.) as biological control agents of R. solani and identified the most effective of these endophytic fungi. Of 577 endophytic fungal isolates studied, rapid mycelial growth over R. solani was shown by sterile mycelia (SM EF-ds61-73, SM EF-ds375-97), EF-ds68-129, Geotrichum sp. EF-ds104-16 and Mucor sp. EFds158-2 in in vitro pre-screening tests. In dual culture tests, however, EF-ds68-129, Geotrichum sp. EFds104-16 and SM EF-ds375-97 exhibited mycelial growth increments of 17.0, 13.3 and 14.2 mm, respectively, resulting in 24% growth inhibition of R. solani. Closer observation revealed that only Geotrichum sp. EF-ds104-16 showed hyperparasitism through coiling and disruption of R. solani hyphae at 6 and 8 days after initial contact. Keywords—Endophytic fungi, barnyard grass, Echinochloa glabrescens, sheath blight, Rhizoctonia solani, weed, rice, biological control, hyperparasitism, dual culture