New Disease Reports (2009) 19, 36.

Molecular identification of Maize streak virus reveals the first evidence for a subtype A1 isolate infecting maize in Cameroon

W.N. Leke 1,2, D.K. Njualem 1, V.P. Nchinda 1, Z. Ngoko 1, S. Zok 3, J.M. Ngeve 3, J.K. Brown 4 and A. Kvarnheden 2*

*anders.kvarnheden@vbsg.slu.se

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Accepted: 05 May 2009

Maize streak virus (MSV; genus Mastrevirus) causes significant damage to maize (Zea mays) in Africa. To date, only strain A of MSV has been associated with maize streak disease in Africa (Varsani et al., 2008). In Cameroon, maize streak is thought to be one of the most important maize diseases. It occurs routinely in the Western Highlands at a reported incidence of 20-50% (Cardwell et al., 1997; Ngoko et al., 2001), and at approximately 90% incidence in 2007. To confirm the presence of MSV and to identify the strain, leaf samples were collected from three symptomatic maize plants in Bambui, North West Province, Cameroon (Fig. 1). The samples were pressed and dried, and the DNA was extracted using Extract-n-Plant PCR (Sigma) (Shepherd et al., 2008). Extracts were subjected to rolling cycle amplification (RCA). Digestion of the single RCA product with either BamHI or KpnI yielded an expected size fragment of ~2.7 kb. The BamHI or KpnI fragments from one sample were cloned and the DNA sequence for each was determined bi-directionally. The sequences were 2689 nucleotides in length, and were identical (GenBank Accession No. FM210279).

A BLAST search of GenBank revealed the highest nucleotide identity, at 99%, to two Nigerian subtype A1 isolates from native grasses, MSV-A1[NG:Abe:07] (EU628566) and MSV-A1[NG:Ile:07] (EU628567), and with the Kenyan maize isolate MSV-A1[KE:Ama:98] (AF329878). Phylogenetic analyses with representative MSV strains and subtypes further supported classification of the Cameroon isolate (MSV-A1[Cameroon: Bambui: 2008]) to subtype MSV-A1 (Fig. 2). This is the first molecular evidence for MSV in Cameroon, and the first report of an A subgroup isolate there.

Figure1+
Figure 1: Maize streak virus symptoms on a maize plant in Bambui, North West Province, Cameroon
Figure 1: Maize streak virus symptoms on a maize plant in Bambui, North West Province, Cameroon
Figure2+
Figure 2: Neighbour–joining analysis using MEGA 4.0 showing predicted relationships between Maize streak virus (MSV) isolates based on the alignment of complete nucleotide sequences. The MSV isolate from Cameroon determined in this study is indicated in bold. Horizontal lines are in proportion to the number of nucleotide differences between branch nodes. Numbers represent bootstrap values for 500 replicates. Only bootstrap values higher than 70 percent are shown. GenBank accession numbers are specified in the tree
Figure 2: Neighbour–joining analysis using MEGA 4.0 showing predicted relationships between Maize streak virus (MSV) isolates based on the alignment of complete nucleotide sequences. The MSV isolate from Cameroon determined in this study is indicated in bold. Horizontal lines are in proportion to the number of nucleotide differences between branch nodes. Numbers represent bootstrap values for 500 replicates. Only bootstrap values higher than 70 percent are shown. GenBank accession numbers are specified in the tree

Acknowledgements

This research was supported by the International Foundation for Science (WN Leke), Swedish Institute (WN Leke), Rothamsted International - African Fellows Programme, and USAID IPM-CRSP Global Themes project, Insect Transmitted Viruses.


References

  1. Cardwell KF, Schulthess F, Ndemah R, Ngoko Z, 1997. A systems approach to assess crop health and maize yield losses due to pests and diseases in Cameroon. Agriculture, Ecosystems and Environment 65, 33-47.
  2. Ngoko Z,Cardwell KF, Marasas WFO, Wingfield MJ, Ndemah R, Schulthess F, 2001. Biological and physical constraints on maize production in the HumidForest and WesternHighlands of Cameroon. European Journal of Plant Pathology 108, 893-902.
  3. Shepherd DN, Martin DP, Lefeuvre P, Monjane AL, Owor BE, Rybicki EP, Varsani A, 2008. A protocol for the rapid isolation of full geminivirus genomes from dried plant tissue. Journal of Virological Methods 149, 97-102.
  4. Varsani A, Shepherd DN, Monjane AL, Owor BE, Erdmann JB, Rybicki EP, Peterschmitt M, Briddon RW, Markham PG, Oluwafemi S, Windram OP, Lefeuvre P, Lett J-M, Martin DP, 2008. Recombination, decreased host specificity and increased mobility may have driven the emergence of maize streak virus as an agricultural pathogen. Journal of General Virology 89, 2063-2074.

This report was formally published in Plant Pathology

©2009 The Authors