Botourmiaviridae is a newly established virus family which relates to Narnaviridae, Mitoviridae and Leviviridae, according to current taxonomic information from International Committee on Taxonomy of Viruses (ICTV, Virus Taxonomy: 2019 Release), the family Botourmiaviridae includes four approved genera, Botoulivirus, Magoulivirus, Scleroulivirus and Ourmiavirus. Members of the genus Ourmiavirus are plant viruses with a bacilliform virion structure, whose genome usually contain three (+) ssRNA segments, encoding RNA-dependent RNA polymerase (RdRp), coat protein (CP), and movement protein (MP), respectively [6]. Since the MP and CP of ourmiaviruses showed significant similarity to other plant viruses, including tombusviruses and sobemovirus, it was proposed that ourmiavirus might have evolved by reassortment of genomic segments from viruses infecting fungi and plants [15]. Members of the genera Botoulivirus, Magoulivirus, and Scleroulivirus are mycoviruses. Similar to narnaviruses and mitoviruses, only one (+) ssRNA segment encoding RdRp has been identified in all of these ourmia-like mycoviruses, and one (+) ssRNA segment was demonstrated to be sufficient for replication, infection and transmission [20]. Ourmia-like mycovirus associated satellite-like RNAs also have been recognized in Magnaporthe oryzae, which are not essential for virus replication [14].
The filamentous fungus M. oryzae (teleomorph) (Herbert ) Barr (anamorph: Pyricularia oryzae ) [2] causes the rice blast disease, which is one of the most serious diseases of cultivated rice worldwide, resulting an approximately 30% annual yield loss [16]. Recently, a number of mycoviruses from different families have been identified in M. oryzae. Magnaporthe oryzae virus 1, 2 and 3 (MoV1, MoV2 and MoV3) are dsRNA viruses which belong to the family Totiviridae [12, 17, 21]. Magnaporthe oryzae chrysovirus 1 (MoCV1) is a dsRNA virus belong to the family Chrysoviridae [4, 18, 19], Magnaporthe oryzae partitivirus 1 (MoPV1) is a dsRNA virus which belong to the family Partitiviridae [3]. Magnaporthe oryzae virus A (MoVA) is an unclassified (+) ssRNA virus that is related to members of the family Tombusviridae [1]. Magnaporthe oryzae narnavirus virus 1 (MoNV1) is a (+)ssRNA virus which belong to the family Narnaviridae [10]. (+) ssRNA viruses belong to the family Botourmiaviridae also have been recognized in M. oryzae, including Magnaporthe oryzae ourmia-like virus 1 and 4 (MOLV1 and MOLV4), Pyricularia oryzae ourmia-like virus 1, 2 and 3 (PoOLV1, PoOLV2 and PoOLV3) Magnaporthe oryzae botourmiavirus 5, 6 and 7 (MoBV5, MoBV6 and MoBV7) [5, 9, 11, 14 ].
In this study, we report a novel mycovirus of the family Botourmiaviridae in M. oryzae strain SH05. Since 8 viruses with in the family Botourmiaviridae from M. oryzae in have been reported, this virus was temporarily named as Magnaporthe oryzae botourmiavirus 9 (MoBV9).