Caracterização morfológica e molecular (ITS-rDNA) de fungos Rhizoctonia isolados de solos brasileiros

Abstract

Fungi of the genus Rhizoctonia constitute a complex taxonomic group of phytopathogens, comprising multinucleated species such as Rhizoctonia zeae and Rhizoctonia orizae, having as Waitea teleomorph, besides numerous species denominated generically of binucleate Rhizoctonia. This genus of fungi is distinguished by the inclusion of globally distributed organisms found in both agricultural soils and forest soils, which can be attributed to leaf-burning symptoms, as well as diseases of roots and other parasitic plant organs. Identifying and characterizing phytopathogenic fungi of the genus Rhizoctonia becomes relevant as soon as symptoms of their presence begin to appear in plants in the various cultures in which they can become hosts. In the present work, 47 isolates of Rhizoctonia fungi obtained from soil samples from different Brazilian regions were identified through molecular methods, morphological characterization and coloration of nuclei, all of which had their ITS-rDNA genomic region successfully sequenced, confirming the identity of each isolate. The three main Rhizoctonia species related to phytopathogens were identified in the different areas studied, with emphasis on R. solani (AG4-HGI), whose isolates corresponded to 25,5% of the samples analyzed. The color of the mycelium of the isolates varied between shades of white, orange, brown and the disposition of the sclerotia in plaque, as well as the nuclear condition of the isolates also presented variability. The results found here confirm previous studies and may represent an important contribution to the management and control of this important group of phytopathogens.