New Disease Reports (2017) 36, 11. [http://dx.doi.org/10.5197/j.2044-0588.2017.036.011]
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First report of Maize yellow mosaic virus infecting maize in Ecuador

A. Bernreiter 1*, R. Garcia Teijeiro 1, D. Jarrin 2, P. Garrido 2 and L. Ramos 2

*mapsylno@live.de

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Received: 24 Aug 2017; Published: 29 Sep 2017

Keywords: Polerovirus, Luteoviridae, viral plant disease, Zea mays

Maize yellow mosaic virus (MaYMV) was first described in maize (Zea mays) from China and proposed as a new virus in the genus Polerovirus (Chen et al., 2016). Recently, MaYMV was also detected in symptomatic maize plants in Burkina Faso (Palanga et al., 2017) indicating a global distribution for the virus. In May 2016 maize plants showing leaf chlorosis and downward curling of leaf tips were collected from a large production area (c. 125,000 hectares in maize cultivation) in the Los Rios Province in Ecuador. It has been estimated that the disease causes yield losses of 10-30%. 

Total RNA from symptomatic leaf samples was extracted using the RNeasy Plant Mini Kit (Qiagen, USA) and subjected to deep sequencing analysis using the Illumina platform. Quality filtered paired end reads (8,777,028) were aligned with reference genomes of known plant viruses using standard bioinformatic tools. The transcriptome was highly enriched with viral RNA reads (>5%) showing significant similarity with Sugarcane mosaic virus (SCMV) and other MaYMV sequences. These short reads were assembled into contigs and full-length and nearly full-length genome sequences of SCMV (9632 nt; Genbank Accession No. K006657) and MaYMV (5488 nt; KY052793) were identified. Alignments and phylogenetic trees were performed using SeaView software (Gouy et al., 2010).

The Ecuadorian MaYMV isolate had the highest nucleotide identity (96%) with a Chinese isolate (KU291103). MaYMV has a typical Polerovirus organisation with six open reading frames (ORFs; 0-5) including ORF3a. ORF3a is translated from a non-standard start codon (in this case AUA) and encodes a protein responsible for long distance movement of the virus in plants (Smirnova et al., 2015). ORF3a (nt 3389-3523) shows a single amino acid substitution compared with the Chinese isolate (KU291103). ORF0 (nt 42-836) shows 97% amino acid identity with MaYMV isolate KU291100 (Table 1) and harbours an essential F-box like element (Pazhouhandeh et al., 2006). The phylogenetic tree (Fig. 1) constructed from ORF0 amino acid sequences indicates significant similarity to the Chinese MaYMV isolate and high variability between different species of the genus Polerovirus. Phylogenetic analysis of ORF3 from selected species of the genera EnamovirusLuteovirus and Polerovirus places the Ecuadorian isolate within a group of poleroviruses that infect a wide range of host plants (Fig. 2).

MaMYV has been reported to be generally present in mixed infections with other viruses, including Maize chlorotic mottle virus, Southern rice black-streaked dwarf virus or SCMV, but has also been found in single infections in China (Chen et al., 2016) displaying characteristic disease symptoms. The significance of mixed infections with SCMV in disease pathology in Ecuador is unclear and requires further investigation. 

Figure1+
Figure 1: Phylogenetic analysis of Maize yellow mosaic virus (MaYMV; KY052793) and other members of the Luteoviridae (A) Comparison of the deduced amino acid sequences of ORF0 proteins and generation of a tree using the neighbour-joining method. Numbers represent bootstrap values (%) calculated from 1000 bootstrap replicates. Scale bar represents number of amino acid substitutions per site. (B) Multiple alignment of the N-terminal region from ORF0 including the conserved F-box like motif LpxxL/I. BVG, Barley virus G; BMYV, Beet mild yellowing virus; BWYV, Beet western yellows virus; BChV, Beet chlorosis virus; CtRLV, Carrot red leaf virus; CYDV, Cereal yellow dwarf virus; ChCSV, Chickpea chlorotic stunt virus; CABYV, Cucurbit aphid-borne yellows virus; MYDV, Maize yellow dwarf virus.
Figure 1: Phylogenetic analysis of Maize yellow mosaic virus (MaYMV; KY052793) and other members of the Luteoviridae (A) Comparison of the deduced amino acid sequences of ORF0 proteins and generation of a tree using the neighbour-joining method. Numbers represent bootstrap values (%) calculated from 1000 bootstrap replicates. Scale bar represents number of amino acid substitutions per site. (B) Multiple alignment of the N-terminal region from ORF0 including the conserved F-box like motif LpxxL/I. BVG, Barley virus G; BMYV, Beet mild yellowing virus; BWYV, Beet western yellows virus; BChV, Beet chlorosis virus; CtRLV, Carrot red leaf virus; CYDV, Cereal yellow dwarf virus; ChCSV, Chickpea chlorotic stunt virus; CABYV, Cucurbit aphid-borne yellows virus; MYDV, Maize yellow dwarf virus.
Figure2+
Figure 2: Phylogenetic tree showing the relationship of Maize yellow mosaic virus (MaYMV; KY052793) and selected Luteoviridae based on the coat protein (CP) (A) and movement protein (MP) (B). Amino acid sequences were aligned and a corresponding neighbour-joining tree with values of 1000 bootstrap replicates is shown. Scale bar represents number of amino acid substitutions per site. BYDV, Barley yellow dwarf virus; BVG, Barley virus G; BLRV, Bean leafroll virus; BMYV, Beet mild yellowing virus; BWYV, Beet western yellows virus; BChV, Beet chlorosis virus; CtRLV, Carrot red leaf virus; CYDV, Cereal yellow dwarf virus; ChCSV, Chickpea chlorotic stunt virus; CABYV, Cucurbit aphid-borne yellows virus; MYDV, Maize yellow dwarf virus; PEMV, Pea enation mosaic virus; RSDaV, Rose spring dwarf-associated virus; SbDV, Soybean dwarf virus; ScYLV, Sugarcane yellow leaf virus; TVDV, Tobacco vein distorting virus; WYDV, Wheat yellow dwarf virus.
Figure 2: Phylogenetic tree showing the relationship of Maize yellow mosaic virus (MaYMV; KY052793) and selected Luteoviridae based on the coat protein (CP) (A) and movement protein (MP) (B). Amino acid sequences were aligned and a corresponding neighbour-joining tree with values of 1000 bootstrap replicates is shown. Scale bar represents number of amino acid substitutions per site. BYDV, Barley yellow dwarf virus; BVG, Barley virus G; BLRV, Bean leafroll virus; BMYV, Beet mild yellowing virus; BWYV, Beet western yellows virus; BChV, Beet chlorosis virus; CtRLV, Carrot red leaf virus; CYDV, Cereal yellow dwarf virus; ChCSV, Chickpea chlorotic stunt virus; CABYV, Cucurbit aphid-borne yellows virus; MYDV, Maize yellow dwarf virus; PEMV, Pea enation mosaic virus; RSDaV, Rose spring dwarf-associated virus; SbDV, Soybean dwarf virus; ScYLV, Sugarcane yellow leaf virus; TVDV, Tobacco vein distorting virus; WYDV, Wheat yellow dwarf virus.
Figure3+

Acknowledgements

The authors are thankful to SENESCYT Ecuador (Prometeo Project) and Agrocalidad, Ecuador for their financial support.


References

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To cite this report: Bernreiter A, Garcia Teijeiro R, Jarrin D, Garrido P, Ramos L, 2017. First report of Maize yellow mosaic virus infecting maize in Ecuador. New Disease Reports 36, 11. [http://dx.doi.org/10.5197/j.2044-0588.2017.036.011]

©2017 The Authors