Maize yellow mosaic virus interacts with maize chlorotic mottle virus and sugarcane mosaic virus in mixed infections, but does not cause maize lethal necrosis

Authors: Stewart, Lucy; Willie, Kristen

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/16/2021
Publication Date: 3/18/2021
Citation: Stewart, L.R., Willie, K.J. 2021. Maize yellow mosaic virus interacts with maize chlorotic mottle virus and sugarcane mosaic virus in mixed infections, but does not cause maize lethal necrosis. Plant Disease. Article 33736468. https://doi.org/10.1094/PDIS-09-20-2088-RE.
DOI: https://doi.org/10.1094/PDIS-09-20-2088-RE

Interpretive Summary: A ubiquitous maize-associated polerovirus has been described in East Africa, Asia, and South America concurrent with emergence of the devastating synergistic disease maize lethal necrosis (MLN). MLN is caused by synergistic (having more than additive effect) co-infection of two viruses: maize chlorotic mottle virus (MCMV) and a maize potyvirus such as sugarcane mosaic virus (SCMV). In field settings, MCMV, SCMV, or both together frequently occur in plants also infected with the maize polerovirus. However, the pathological impact, if any, of the polerovirus in these mixed infections was not known. We tested the impact of polerovirus on disease development measured by stunting, reddening, mosaic, and necrosis in plants with mixed infections compared to single infections. Experiments addressed the questions of whether polerovirus causes disease in infected plants and whether it impacts disease symptom development in double and triple infections with MCMV and SCMV. Results showed that the polerovirus does contribute to disease, causing plant stunting and distinct leaf reddening, in single and mixed infections, and can interact with co-infecting viruses, but is not synergistic with MLN viruses. These results provide new insight for growers, researchers, and epidemiologists to understand the role of maize polerovirus in field settings, including the distinct polerovirus symptoms and lack of synergistic impact of the polerovirus.

Technical Abstract: A maize-associated polerovirus, variously named maize yellow dwarf virus RMV2 (MYDV RMV2), MYDV-like, and maize yellow mosaic virus (MaYMV), has been described in East Africa and many other global locations. This virus was discovered in deep sequencing studies precipitated by maize lethal necrosis (MLN) emergence and is frequently found in mixed infections with viruses known to synergistically cause MLN in co-infections: maize chlorotic mottle virus (MCMV) and sugarcane mosaic virus (SCMV). MaYMV has also been reported at high incidence and is prevalent in all locations where deep sequencing for MLN has been done. We examined how MaYMV impacted disease development in mixed infections with MCMV, SCMV, and both MCMV and SCMV. Results demonstrated the MaYMV symptoms include stunting as well as leaf reddening, and that it interacts with titer of the other viruses and can enhance some symptoms in mixed infections. However, MaYMV mixed infection did not recapitulate MLN synergistic disease in the absence of either of the known MLN viruses. These data inform the potential disease impact of this newly discovered ubiquitous maize virus, alone and in the context of MLN viruses.