First occurrence of dsRNA in Rhizoctonia solani AG2-2 LP from turfgrass Zoysia japonica in Brazil / Primeiro relato de RNA dupla fita em Rhizoctonia solani AG2-2 LP, patógeno de Zoysia japônica no Brasil

Abstract

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 their first report in the 1960s, they have been searched for in many classes of fungi with the purpose of finding new tools to manage diseases, improve crops and address the challenges of climate change. The genome of mycoviruses mostly consists of double-stranded RNA (dsRNA) and they may or may not induce symptoms in their host. dsRNAs have already been reported in species of Rhizoctonia, in some cases reducing virulence . We searched for dsRNAs in 12 Brazilian isolates of R. solani AG 2-2 LP, a pathogen of zoysiagrass. All isolates showed dsRNAs were present in a similar profile to each other, irrespective of the virulence of those isolates on zoysiagrass. Among the isolates the number of dsRNA segments ranged from three to eight, with different sizes, never smaller than 2 kb and with segments greater than 10 Kb in all isolates. Detection of dsRNA in all R. solani isolates may be indicative of mycoviruses being a frequent presence in these fungi.