Department of Phytopathology, Institute of Sugar Beet Research, Göttingen, Germany.
Institute of Horticultural Production Systems, Plant Virology, Department of Phytomedicine, Leibniz University, Hannover, Germany.
J Gen Virol. 2022 Aug;103(8). doi: 10.1099/jgv.0.001777.
The A-type of beet necrotic yellow vein virus (BNYVV) is widely distributed in Europe and is one of the major virus types causing rhizomania disease in sugar beet. The closely related P-type is mainly limited to a small region in France (Pithiviers). Both virus types possess four RNAs (RNA1-4), but the P-type harbours an additional fifth RNA species (RNA5). The P-type is associated with stronger disease symptoms and resistance-breaking of , one of the two resistance genes which are used to control BNYVV infection. These characteristics are presumably due to the presence of RNA5, but experimental evidence for this is lacking. We generated the first infectious cDNA clone of BNYVV P-type to study its pathogenicity in sugar beet in comparison to a previously developed A-type clone. Using this tool, we confirmed the pathogenicity of the P-type clone in the experimental host and two species, and . Independent of RNA5 both the A- and the P-type accumulated in lateral roots and reduced the taproot weight of a susceptible sugar beet genotype to a similar extent. In contrast, only the P-type clone was able to accumulate a virus titre in an -resistant variety whereas the A-type clone failed to infect this variety. The efficiency of the P-type to overcome resistance was strongly associated with the presence of RNA5. Only a double resistant variety, harbouring and prevented an infection with the P-type. Reassortment experiments between the P- and A-type clones demonstrated that both virus types can exchange whole RNA components without losing the ability to replicate and to move systemically in sugar beet. Although our study highlights the close evolutionary relationship between the two virus types, we were able to demonstrate distinct pathogenicity properties that are attributed to the presence of RNA5 in the P-type.
A 型芜菁黄花叶病毒（BNYVV）广泛分布于欧洲，是引起甜菜根腐病的主要病毒类型之一。与之密切相关的 P 型主要局限于法国的一个小区域（皮蒂维耶尔）。两种病毒类型都拥有 4 个 RNA（RNA1-4），但 P 型还拥有一个额外的第五个 RNA 物种（RNA5）。P 型与更强的病症和一种抗性基因（用于控制 BNYVV 感染的两个抗性基因之一）的抗性丧失有关。这些特征可能归因于 RNA5 的存在，但缺乏实验证据。我们生成了 BNYVV P 型的首个传染性 cDNA 克隆，以研究其在甜菜中的致病性，并与之前开发的 A 型克隆进行比较。使用该工具，我们在实验宿主 和两个 物种 和 中证实了 P 型克隆的致病性。独立于 RNA5，A 型和 P 型都在侧根中积累，并以相似的程度降低了易感甜菜基因型的主根重量。相比之下，只有 P 型克隆能够在抗品种中积累病毒滴度，而 A 型克隆无法感染该品种。P 型克服 抗性的效率与 RNA5 的存在密切相关。只有同时携带 和 抗性的双抗性品种才能阻止 P 型的感染。P-和 A-型克隆之间的重组实验表明，两种病毒类型都可以交换整个 RNA 成分，而不会失去复制和在甜菜中系统传播的能力。尽管我们的研究强调了两种病毒类型之间的密切进化关系，但我们能够证明 P 型存在 RNA5 所赋予的独特致病性特征。
