Kenya Agricultural and Livestock Research Organization (KALRO), P. O. Box 14733-00800, Nairobi, Kenya.
Department of Plant Pathology and Nebraska Center for Virology, University of Nebraska- Lincoln, Lincoln, NE, 68583, USA.
Virol J. 2018 May 23;15(1):90. doi: 10.1186/s12985-018-0999-2.
Maize lethal necrosis is caused by a synergistic co-infection of Maize chlorotic mottle virus (MCMV) and a specific member of the Potyviridae, such as Sugarcane mosaic virus (SCMV), Wheat streak mosaic virus (WSMV) or Johnson grass mosaic virus (JGMV). Typical maize lethal necrosis symptoms include severe yellowing and leaf drying from the edges. In Kenya, we detected plants showing typical and atypical symptoms. Both groups of plants often tested negative for SCMV by ELISA.
We used next-generation sequencing to identify viruses associated to maize lethal necrosis in Kenya through a metagenomics analysis. Symptomatic and asymptomatic leaf samples were collected from maize and sorghum representing sixteen counties.
Complete and partial genomes were assembled for MCMV, SCMV, Maize streak virus (MSV) and Maize yellow dwarf virus-RMV (MYDV-RMV). These four viruses (MCMV, SCMV, MSV and MYDV-RMV) were found together in 30 of 68 samples. A geographic analysis showed that these viruses are widely distributed in Kenya. Phylogenetic analyses of nucleotide sequences showed that MCMV, MYDV-RMV and MSV are similar to isolates from East Africa and other parts of the world. Single nucleotide polymorphism, nucleotide and polyprotein sequence alignments identified three genetically distinct groups of SCMV in Kenya. Variation mapped to sequences at the border of NIb and the coat protein. Partial genome sequences were obtained for other four potyviruses and one polerovirus.
Our results uncover the complexity of the maize lethal necrosis epidemic in Kenya. MCMV, SCMV, MSV and MYDV-RMV are widely distributed and infect both maize and sorghum. SCMV population in Kenya is diverse and consists of numerous strains that are genetically different to isolates from other parts of the world. Several potyviruses, and possibly poleroviruses, are also involved.
玉米坏死性萎蔫病是由玉米褪绿斑驳病毒（MCMV）与马铃薯 Y 病毒科（Potyviridae）的特定成员（如甘蔗花叶病毒（SCMV）、小麦线条花叶病毒（WSMV）或约翰逊草花叶病毒（JGMV））协同感染引起的。典型的玉米坏死性萎蔫症状包括叶片严重发黄和边缘干枯。在肯尼亚，我们检测到表现出典型和非典型症状的植物。两组植物通常通过 ELISA 检测对 SCMV 呈阴性。
我们通过宏基因组分析，使用下一代测序技术鉴定与肯尼亚玉米坏死性萎蔫相关的病毒。采集来自 16 个县的玉米和高粱的有症状和无症状叶片样本。
组装了 MCMV、SCMV、玉米条纹病毒（MSV）和玉米黄矮病毒-RMV（MYDV-RMV）的完整和部分基因组。在 68 个样本中的 30 个样本中发现了这四种病毒（MCMV、SCMV、MSV 和 MYDV-RMV）。地理分析表明，这些病毒在肯尼亚广泛分布。核苷酸序列的系统发育分析表明，MCMV、MYDV-RMV 和 MSV 与东非和世界其他地区的分离物相似。单核苷酸多态性、核苷酸和多蛋白序列比对确定了肯尼亚 SCMV 的三个遗传上不同的群体。变异映射到 Ni b 和外壳蛋白边界的序列。获得了其他四种马铃薯 Y 病毒和一种线条病毒的部分基因组序列。
我们的研究结果揭示了肯尼亚玉米坏死性萎蔫病流行的复杂性。MCMV、SCMV、MSV 和 MYDV-RMV 广泛分布，感染玉米和高粱。肯尼亚的 SCMV 群体多样，由许多与世界其他地区分离物在遗传上不同的菌株组成。还涉及几种马铃薯 Y 病毒和可能的线条病毒。
