Hall J S, French R, Hein G L, Morris T J, Stenger D C
Agricultural Research Service-United States Department of Agriculture, University of Nebraska, Lincoln, Nebraska 68583, USA.
Virology. 2001 Apr 10;282(2):230-6. doi: 10.1006/viro.2001.0841.
Cross-protection and vector transmission bottlenecks have been proposed as mechanisms facilitating genetic isolation of sympatric viral lineages. Molecular markers were used to monitor establishment and resolution of mixed infections with genetically defined strains of wheat streak mosaic virus (WSMV). Two closely related WSMV strains from the U.S. (Type and Sidney 81) exhibited reciprocal cross-protection in wheat, confirming this classic phenomenon as a mechanism of genetic isolation. In contrast, cross-protection between either U.S. strain and the divergent El Batán 3 strain from Mexico was unilateral, erratic, and only partially effective. Distribution of WSMV strains within individual leaves of plants supporting a mixed infection of Type and Sidney 81 was spatially nonuniform. Strain distribution among individual tillers of coinfected plants also was heterogeneous, with some containing either Type or Sidney 81 alone and some containing both. Transmission by wheat curl mites, acquiring virus from source plants simultaneously infected with both Type and Sidney 81, often resulted in test plants bearing only a single WSMV strain. Spatial subdivision of virus strains within coinfected plants likely contributed to vector transmission bottlenecks during acquisition. Collectively, these three distinct mechanisms enhance genetic isolation of individual viral lineages, and together with stochastic processes, may explain generation and maintenance of genetic diversity in field populations.
交叉保护和媒介传播瓶颈被认为是促进同域病毒谱系遗传隔离的机制。分子标记被用于监测小麦条纹花叶病毒（WSMV）基因定义毒株混合感染的建立和消退。来自美国的两个密切相关的WSMV毒株（类型毒株和西德尼81毒株）在小麦中表现出相互交叉保护，证实了这一经典现象是一种遗传隔离机制。相比之下，美国的任何一个毒株与来自墨西哥的不同的埃尔巴坦3毒株之间的交叉保护是单向的、不稳定的，且仅部分有效。支持类型毒株和西德尼81毒株混合感染的植物单叶内WSMV毒株的分布在空间上是不均匀的。同时感染两种毒株的植株个体分蘖间的毒株分布也存在异质性，有些仅含有类型毒株或西德尼81毒株，有些则同时含有两种毒株。从小麦卷叶螨传播病毒来看，从小麦卷叶螨同时从同时感染类型毒株和西德尼81毒株的源植物中获取病毒，往往导致试验植株仅携带单一的WSMV毒株。同时感染植株内病毒毒株的空间细分可能导致获取过程中的媒介传播瓶颈。总体而言，这三种不同机制增强了单个病毒谱系的遗传隔离，并且与随机过程一起，可能解释了田间种群遗传多样性的产生和维持。
