Zoysia japonica , in Brazil, is commonly infected by Rhizoctonia solani ( R. solani ) in humid and cool weather conditions. Eight isolates of R. solani , previously identified as belonging to the AG2-2 LP anastomosis group, isolated from samples from large path symptoms, were collected from three counties in São Paulo state (Brazil) and investigated for the presence of mycoviruses. After detection of double-strand RNA (dsRNA) in all samples, RNA_Seq analysis of ribosomal RNA-depleted total RNA from in vitro cultivated mycelia was performed. Forty-seven partial or complete viral unique RNA dependent-RNA polymerase (RdRp) sequences were obtained with a high prevalence of positive sense ssRNA viruses. Sequences were sufficiently different from the first match in BLAST searches suggesting that they all qualify as possible new viral species, except for one sequence showing an almost complete match with Rhizoctonia solani dsRNA virus 2, an alphapartitivirus. Surprisingly four large contigs of putative viral RNA could not be assigned to any existing clade of viruses present in the databases, but no DNA was detected corresponding to these fragments confirming their viral replicative nature. This is the first report on the occurrence of mycoviruses in R. solani AG2-2 LP in South America.

The use of cultivated grasses in Brazil has grown by 40% between 2010 and 2015, and the species Zoysia japonica Steud, especially the cultivar ‘Esmeralda’, corresponds to 81% of the grass market in the country. The most important disease affecting zoysia grass, known as large patch, is caused by Rhizoctonia solani and occurs in the Brazilian lawns particularly during winter months. The aim of this study was to contribute to the identification and characterization of the anastomosis group of R. solani isolates from lesions typical of large patch collected from ‘Esmeralda’ grass at gardens and golf courses in the states of São Paulo and Bahia, Brazil. All 12 obtained isolates presented dark-brown colonies with aerial mycelial growth, multinucleated hyphae and absence of concentric zonation or sclerotia, and showed their greatest mycelial growth rate at 25°C. In pathogenicity experiments, except three out of R. solani isolates, reduced the growth of zoysia grass. Based on the analysis of sequences of the rDNA-ITS region, the isolates clustered with reference isolates of the anastomosis group AG 2-2 LP. Phylogenetic inference showed that the Brazilian isolates are grouped into two clades that shared the same common ancestral with 96% bootstrap. One of the clades includes only Brazilian isolates while the other one also includes American and Japanese R. solani isolates AG 2-2 LP. This is the first report and characterization of R. solani AG 2-2 LP in zoysiagrass in Brazil.

Mycovirus are viruses that infect all taxa of fungi.They are generally cryptic or latent, but they can induce minor or imperceptible changes in hosts. Mycoviruses can interfere with the symptoms induced by phytopathogenic fungi hosts, and in some cases they reduce the virulence of its host. Therefore, they are objects of study since they are potential biocontrol agents and are important tools for knowledge of fungal pathogenesis mechanisms. The aim of this review was to gather literature data concerning general aspects of biology and behavior of mycovirus, focusing some phytopathogenic mycovirus.KEYWORDS: mycovirus; biocontrol; hypovirulence; vegetative incompatibility. RESUMO: Micovírus são vírus que infectam todos os taxa de fungos.São geralmente crípticos (latentes), mas podem causar pequenas ou imperceptíveis alterações no hospedeiro. Nos fungos fitopatogênicos, os vírus podem interferir com os sintomas e, em alguns casos, reduzir a virulência de seu hospedeiro; por esta razão, são objeto de estudo, por serem um potencial agente de biocontrole e por serem ferramentas importantes para o conhecimento sobre os mecanismos de patogênese de fungos. A presente revisão teve o objetivo de reunir os dados de literatura relacionados aos aspectos gerais da biologia e do comportamento dos micovírus presentes em alguns fungos fitopatogênicos. PALAVRAS-CHAVE: micovírus; biocontrole; hipovirulência;incompatibilidade vegetativa.

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Rhizoctonia solani, a complex species comprising groups and sub-groups of somatic compatibility (anastomosis groups -AG), is a cosmopolitan pathogenic fungus that causes important diseases in a wild range of plants. One example is R. solani AG2-2 LP, the causal agent of large patch disease of C4 grasses, primarily zoysiagrass. The occurrence of this pathogen in Brazil causes a severe disease that is difficult to control. Mycoviruses, viruses that replicate in fungi, are ubiquitous. Since