Cross-kingdom Viral Infection Of Cucumber Mosaic Virus In Plant And Phytopathogenic Fungi

Mycoviruses or fungal viruses that infect fungi reign in all major taxonomic groups of fungi.Up to now,it is still not clear that where the mycovirus come from.There are currently two hypotheses;one hypothesis believes that plant viruses evolved into fungal viruses during a relatively recent period when both plant viruses and plant pathogenic fungi coinfect plants and another hypothesis is that some plant viruses may be derived from fungal viruses.Mycoviruses mostly infect their hosts persistently and benignantly.Nevertheless,some mycoviruses,upon infection,can bring about hypovirulence(ability to produce less disease severity than normal)and other associated phenotypic changes including irregular hyphal growth,atypical pigmentation,and reduced sporulation to their hosts.Mycoviruses with the ability to diminish host virulence usually come under the spotlight as these can be exploited as biological control agents to manage economically important fungal plant pathogens.Rhizoctonia solani is a pathogen of black scurf of potato.It is distributed worldwide and considered to be one of the most destructive soil-borne plant pathogens.Previous studies found that there are many fungal virus resources in Rhizoctonia solani,some of which are attenuated viruses that can affect the pathogenicity of the host,and thus have the potential to be developed as a new type of biological fungicide to control black scurf of potato.In order to scientifically and effectively control the potato black scurf disease in the planting area of Inner Mongolia,the screening and identification of the virus that infects potato black scurf was conducted.In this study,we discovered the natural infection of a plant virus,cucumber mosaic virus(CMV)in the plant pathogenic fungus Rhizoctonia solani.The detail of CMV cross-kingdom infection between plant and phytopathogenic fungi were further explored.The contents of this study included:1、We obtained a CMV-infected R.solani strain from potato plants in Inner Mongolia,China.CMV is one of the plant viruses with the largest host range and the widest distribution and currently the most harmful to agricultural economy.The analysis of sequence indicated CMV-Rs which isolated from R.solani is highly identified to plant viral isolates CMV-Fny.2、When this fungal strain was cultured in the laboratory,the CMV infection was stable.CMV could spread horizontally through hyphal fusion but not vertically through sexual spores.3、When CMV was inoculated by protoplast transfection,CMV replicated in an isolateof R.solani and another phytopathogenic fungus,Vasla mali,suggesting that some fungi could serve as alternative hosts for CMV.4、More importantly,under laboratory conditions,R.solani could acquire CMV frominfected plants and could also transmit the virus to uninfected plants.Altogether,this study provides first evidence of virus transfer between plants and fungi,and further expands our understanding of plant-fungal interactions and plant virus transmission.