Co-infection with a wheat rhabdovirus causes a reduction inMal de Río Cuarto virustiter in its planthopper vector

Abstract

Mal de Río Cuarto virus (MRCV, Fijivirus, Reoviridae) causes one of the most important diseases in maize (Zea mays L.) in Argentina and has been detected in mixed infections with a rhabdovirus closely related to Maize yellow striate virus. In nature both viruses are able to infect maize and several grasses including wheat, and are transmitted in a persistent propagative manner by Delphacodes kuscheli Fennah (Hemiptera: Delphacidae). This work describes the interactions between MRCV and rhabdovirus within their natural vector and the consequences of such co-infection regarding virus transmission and symptom expression. First- and third-instar D. kuscheli nymphs were fed on MRCV-infected wheat plants or MRCV-rhabdovirus-infected oat plants, and two latency periods were considered. Transmission efficiency and viral load of MRCV-transmitting and non-transmitting planthoppers were determined by real-time quantitative polymerase chain reaction analysis (RTqPCR). Vector transmission efficiency was related to treatments (life stages at acquisition and latency periods). Nevertheless, no correlation between transmission efficiency and type of inoculum used to infect insects with MRCV was found. Treatment by third-instar nymphs 17 days after Acquisition Access Period was the most efficient for MRCV transmission, regardless of the type of inoculum. Plants co-infected with MRCV and rhabdovirus showed the typical MRCV symptoms earlier than plants singly infected with MRCV. The transmitting planthoppers showed significantly higher MRCV titers than non-transmitting insects fed on single or mixed inocula, confirming that successful MRCV transmission is positively associated with viral accumulation in the insect. Furthermore, MRCV viral titers were higher in transmitting planthoppers that acquired this virus from a single inoculum than in those that acquired the virus from a mixed inoculum, indicating that the presence of the rhabdovirus somehow impaired MRCV replication and/or acquisition. This is the first study about interactions between MRCV and a rhabdovirus closely related to Maize yellow striate virus in this insect vector (D. kuscheli), and contributes to a better understanding of planthopper-virus interactions and their epidemiological implications.

Insights Into Insect Vector Transmission and Epidemiology of Plant-Infecting Fijiviruses

“…Although most of planthoppers could be viruliferous after feeding on mixedinfected plants, planthoppers with notably higher MRCV titers are able to transmit the virus, meaning that efficient MRCV transmission is positively correlated with virus accumulation in the insect (Argüello Caro et al, 2013). Plants doubly-infected by MRCV and the rhabdovirus showed typical symptoms of MRCV earlier than that single infected with MRCV, but the planthoppers fed on doubly-infected plants only acquired lower MRCV titers and transmitted inefficiency, indicating that these two viruses have antagonism in host plants and vector insects (Dumón et al, 2017).…”

“…Mal de Río Cuarto virus has been detected in co-infection with an isolate of maize yellow striate virus (MYSV, genus Cytorhabdovirus, family Rhabdoviridae) in maize (Dumón et al, 2015(Dumón et al, , 2017. Both viruses can naturally infect maize and several grasses through transmission by D. kuscheli.…”

Rice Gall Dwarf Virus Promotes the Propagation and Transmission of Rice Stripe Mosaic Virus by Co-infected Insect Vectors

“…What we have known is that RTBV (a double-stranded circular DNA virus) is dependent on RTSV (a single-stranded RNA virus) for joint transmission by leafhopper vector N. virescenes (Sta Cruz et al, 2003;Srilatha et al, 2019). By contrast, co-infection with a wheat rhabdovirus inhibits the acquisition and propagation of Mal de Río Cuarto virus, a plant reovirus, in their planthopper vector (Dumón et al, 2017). Similarly, RBSDV limits RSV acquisition and transmission by their planthopper vector (Moya Fernández et al, 2021).…”

Interplay of Rice Stripe Virus and Rice Black Streaked Dwarf Virus during Their Acquisition and Accumulation in Insect Vector

“…Insects have defense systems to avoid virus infection, replication, or release. Therefore, a virus that requires a specific insect vector for successful transmission needs to fend off attack by the insect's immune system and overcome the transmission barriers in the midgut or salivary gland [19,[25][26][27]. Effective transmission by the insect vector thus depends on factors in either the virus itself or the vector.…”