A unique capsidless virus with a positive-sense, single-stranded RNA genome (hadakavirus 1, HadV1), a member of the extended picorna-like supergroup, was isolated previously from the phytopathogenic fungus Fusarium oxysporum. Here, we describe the molecular and biological characterisation of a second hadakavirus strain from Fusarium nygamai, which has not been investigated in detail previously as a virus host. This virus, hadakavirus 1 strain 1NL (HadV1-1NL), has features similar to the first hadakavirus, HadV1-7n, despite having a different number of segments (10 for HadV1-1NL vs. 11 for HadV1-7n). The 10 genomic RNA segments of HadV1-1NL range in size from 0.9 kb to 2.5 kb. All HadV1-1NL segments show 67% to 86% local nucleotide sequence identity to their HadV1-7n counterparts, whereas HadV1-1NL has no homolog of HadV1-7n RNA8, which encodes a zinc-finger motif. Another interesting feature is the possible coding incapability of HadV1-1NL RNA10. HadV1-1NL was predicted to be capsidless based on the RNase A susceptibility of its replicative form dsRNA. Phenotypic comparison of multiple virus-infected and virus-free single-spore isolates indicated asymptomatic infection by HadV1-1NL. Less-efficient vertical transmission via spores was observed as the infected fungal colonies from which the spores were derived became older, as was observed for HadV1-7n. This study shows a second example of a hadakavirus that appears to have unusual features.

先前从植物病原真菌尖孢镰刀菌 ( Fusarium oxysporum ) 中分离出一种独特的无衣壳病毒，具有正链单链 RNA 基因组 (hadakavirus 1, HadV1)，它是扩展的 picorna 样超群的成员。在这里，我们描述了来自Fusarium nygamai的第二个 hadakavirus 毒株的分子和生物学特征，之前没有作为病毒宿主进行过详细调查。这种病毒，即 hadakavirus 1 毒株 1NL (HadV1-1NL)，具有与第一种 hadakavirus HadV1-7n 相似的特征，尽管其片段数量不同（HadV1-1NL 为 10，而 HadV1-7n 为 11）。HadV1-1NL 的 10 个基因组 RNA 片段的大小范围从 0.9 kb 到 2.5 kb。所有 HadV1-1NL 片段与其 HadV1-7n 对应物显示 67% 至 86% 的局部核苷酸序列同一性，而 HadV1-1NL 没有 HadV1-7n RNA8 的同源物，后者编码锌指基序。另一个有趣的特征是 HadV1-1NL RNA10 可能无法编码。根据其复制形式 dsRNA 的 RNase A 敏感性，预测 HadV1-1NL 是无衣壳的。多种病毒感染和无病毒单孢子分离株的表型比较表明 HadV1-1NL 无症状感染。正如对 HadV1-7n 所观察到的那样，随着产生孢子的受感染真菌菌落变老，观察到通过孢子进行的垂直传播效率较低。这项研究显示了哈达卡病毒的第二个例子，它似乎具有不寻常的特征。