Computational Biology Division, Department of Integrative Biomedical Sciences, Institute of Infectious Diseases and Molecular Medicine, University of Cape Town, Observatory, Cape Town, 7925, South Africa.
CIRAD, UMR PVBMT, La Réunion, 97410, Saint Pierre, France.
Arch Virol. 2021 Mar;166(3):955-959. doi: 10.1007/s00705-020-04906-x. Epub 2021 Jan 27.
Maize streak disease (MSD) is one of the most significant biotic constraints on the production of Africa's most important cereal crop. Until recently, the only virus known to cause severe MSD was the A-strain of maize streak virus (MSV/A), a member of the genus Mastrevirus, family Geminiviridae. However, over the past decade, two other mastreviruses, MSV/C and maize streak Réunion virus (MSRV), have been repeatedly found in the absence of MSV/A in maize plants displaying severe MSD symptoms. Here, we report on infectious clones of MSV/C and MSRV and test their ability to cause severe MSD symptoms. Although cloned MSV/C and MSRV genomes could cause systemic symptomatic infections in MSD-sensitive maize genotypes, these infections yielded substantially milder symptoms than those observed in the field. The MSV/C and MSRV isolates that we have examined are therefore unlikely to cause severe MSD on their own. Furthermore, mixed infections of MSRV and MSV/C with other mild MSV strains also consistently yielded mild MSD symptoms. It is noteworthy that MSRV produces distinctive striate symptoms in maize that are similar in pattern, albeit not in severity, to those seen in the field, showing that this virus may contribute to the severe MSD symptoms seen in the field. Therefore, despite not fulfilling Koch's postulates for MSV/C and MSRV as causal agents of severe MSD, we cannot exclude the possibility that these viruses could be contributing to currently emerging maize diseases.
玉米条纹病（MSD）是非洲最重要谷物作物生产的主要生物限制因素之一。直到最近，已知唯一导致严重 MSD 的病毒是玉米条纹病毒的 A 株（MSV/A），它是 Geminiviridae 科 Mastrevirus 属的成员。然而，在过去十年中，另外两种 Mastreviruses，MSV/C 和玉米条纹留尼汪病毒（MSRV），在表现出严重 MSD 症状的玉米植物中，在没有 MSV/A 的情况下反复被发现。在这里，我们报告了 MSV/C 和 MSRV 的感染性克隆，并测试了它们引起严重 MSD 症状的能力。尽管克隆的 MSV/C 和 MSRV 基因组可以在 MSD 敏感的玉米基因型中引起系统性症状感染，但这些感染产生的症状比在田间观察到的要轻得多。因此，我们研究的 MSV/C 和 MSRV 分离株本身不太可能引起严重的 MSD。此外，MSRV 和 MSV/C 与其他温和 MSV 株的混合感染也始终产生温和的 MSD 症状。值得注意的是，MSRV 在玉米中产生独特的条纹症状，其模式与田间观察到的相似，尽管严重程度不同，表明该病毒可能导致田间出现严重的 MSD 症状。因此，尽管 MSV/C 和 MSRV 不符合科赫假设作为严重 MSD 的病原体，但我们不能排除这些病毒可能对当前出现的玉米病有贡献的可能性。
