Identification of a Novel Partitivirus of Trichoderma harzianum NFCF319 and Evidence for the Related Antifungal Activity

Abstract

We have reported 15 agarose gel band patterns of double-stranded RNA (dsRNA) from Trichoderma spp. We describe herein that band pattern IX in Trichoderma harzianum NFCF319, which appeared to be a single band but consisted of two dsRNAs of similar size, was identified as a novel mycovirus, designated Trichoderma harzianum partitivirus 1 (ThPV1). The larger segment (dsRNA1) of the ThPV1 genome comprised 2,289 bp and contained a single open reading frame (ORF) encoding an RNA-dependent RNA polymerase (RdRp). The smaller segment (dsRNA2) consisted of 2,245 bp with a single ORF encoding a capsid protein (CP). Evaluation of the deduced amino acid sequence and phylogenetic analysis indicated that ThPV1 is a new member of the genus Betapartitivirus in the family Partitiviridae. Curing of virus infection by single-sporing generated 31 virus-free single-spore clones. No significant differences in growth rate, conidia production, or pigmentation were observed between ThPV1-infected and -cured isogenic strains. In addition, comparison of the newly ThPV1-transmitted isolates with their ThPV1-cured parental strain showed no significant difference in colony morphology or pigmentation. However, inhibition of growth in co-cultured Pleurotus ostreatus and Rhizoctonia solani by T. harzianum was increased in ThPV1-containing strains compared with ThPV1-cured isogenic strains. Moreover, β-1,3-glucanase activity was significantly increased in the ThPV1-containing strains. However, no difference in chitinase activity was observed, suggesting that ThPV1 regulates the activity of a specific fungal enzyme.

Molecular Characterization of a Debilitation-Associated Partitivirus Infecting the Pathogenic Fungus Aspergillus flavus

“…Members of the family Partitiviridae are usually considered to have latent effect infections of their hosts, such as resistance to salinity, regulation of mycotoxin production or biocontrol potential (Nibert et al, 2014; Nerva et al, 2017, 2018; Chun et al, 2018). However, only few partitiviruses are likely responsible for inducing abnormal phenotypes or virulence reduction in their hosts.…”

“…To date, most partitiviruses are typically associated with no obvious effects on their fugal hosts (Nibert et al, 2014). Recently, some interesting reports have clarified about the role of partitivirus in resistance to salinity, regulation of mycotoxin production, and for affecting biocontrol potential in their hosts (Nerva et al, 2017, 2018; Chun et al, 2018).…”

Isolation, molecular characterization and virome analysis of culturable wood fungal endophytes in esca symptomatic and asymptomatic grapevine plants

“…The hypothesis of positive interactions between fungi and viruses was further confirmed in other fungal‐virus interactions: in a first example, infection by a specific partitivirus brought to enhanced osmotic tolerance of C. parasitica; in a second example, infection with a distinct partitivirus enhanced mycotoxin production in Aspergillus ochraceus (Nerva et al ., , ). Another positive effect on the fungal host was reported during the interaction between a specific partitivirus and an isolate of Trichoderma harzianum : the virus infected isolate displayed an increased antagonistic activity if compared to the virus‐free isogenic isolate (Chun et al ., ). However, the majority of mycoviruses discovered over the last few years appear to have no obvious effects on their hosts and, therefore, they are often designated as cryptic viruses (Ghabrial et al ., ).…”

Extreme Diversity of Mycoviruses Present in Isolates of Rhizoctonia solani AG2-2 LP From Zoysia japonica From Brazil

“…Since the first report in the 1960s, mycoviruses were searched for and found in many classes of phytopathogenic fungi, mostly because some mycoviruses can reduce the capacity of fungi to cause disease and may have the potential application as biological control agents. More recently, mycoviruses were also shown to be important for their environmental role and for modulating intra and inter-species interactions (Drinnenberg et al, 2011; Nerva et al, 2017, 2018a; Chun et al, 2018), possibly mediated by complex tripartite symbiotic relationships (Marquez et al, 2007). Not all the viruses associated with fungal pathogens affect virulence, but some can indeed cause hypovirulence, as is the case of the classic model system Cryphonectria hypovirus 1, infecting Cryphonectria parasitica (Nuss, 2005; Turina and Rostagno, 2007), or the association between Rhizoctonia solani partitivirus 2 (RsPV2) and R. solani AG-1 IA causing hypovirulence on rice (Zheng et al, 2014).…”