Poleroviruses are not mechanically transmittable by sap inoculation, which makes their isolation and multiplication in laboratory hosts for virion extraction and genome sequence analysis difficult. A reverse‐transcription polymerase chain reaction (RT‐PCR) procedure was modified to amplify the entire genomes of cucurbit‐infecting poleroviruses in three sections directly from RNA extracts from infected plant field samples. The procedure was used to determine the first full‐length genome nucleotide sequences of four polerovirus isolates from field samples collected in Taiwan. TW1 was identified as Melon aphid‐borne yellows virus (MABYV), because it had 90% for P3 and P3‐5 and aa identities of 78–88% for all the other proteins. TW19 represents the first full‐length sequence for the recently described Suakwa aphid‐borne yellows virus (SABYV). The deduced aa sequences for all the proteins of TW19 showed >10% variation compared to all other poleroviruses, though recombination analysis suggested MABYV as the major parent and an unidentified polerovirus as minor parent. R‐TW82 was identified as a strain of CABYV, as the deduced CP aa sequence showed >90% identity to that of other CABYV isolates, and recombination analysis suggested that MABYV was the major parent with CABYV the minor parent. Comparative details of the new full‐length sequences and their implications on criteria for distinguishing polerovirus species are discussed.

RNA viruses of the genera Ambivirus, Mitovirus, Sclerotimonavirus, and Partitivirus were found in a single isolate of Fusarium graminearum. The genomes of the mitovirus, sclerotimonavirus, and partitivirus were assigned to previously described viruses, whereas the ambivirus genome putatively represents a new species, named Fusarium graminearum ambivirus 1 (FgAV1). To investigate the effect of mycoviruses on the fungal phenotype, the spontaneous loss of mycoviruses during meiosis and the transmission of mycoviruses into a new strain via anastomosis were used to obtain isogenic F. graminearum strains both with and without mycoviruses. Notable effects observed in mycovirus-harboring strains were (i) the suppression of the synthesis of trichothecene mycotoxins and their precursor trichodiene, (ii) the suppression of the synthesis of the defense compound aurofusarin, (iii) the stimulation of the emission of 2-methyl-1-butanol and 3-methyl-1-butanol, and (iv) the increased attractiveness of fungal mycelia for fungivorous collembolans. The increased attractiveness of mycovirus-infected filamentous fungi to animal predators opens new perspectives on the ecological implications of the infection of fungi with viruses.

Objective: Yam virus X (YVX; Potexvirus ecsdioscoreae ) is a positive-sense, flexuous RNA virus belonging to the family Alphaflexiviridae . It has been first reported from Guadeloupe, a French archipelago located in the Caribbean Sea. In this study, we investigated the virome in yam ( Dioscorea spp.) plant material collected in the state of Bahia (Brazil) by high-throughput sequencing (HTS) on Illumina platform. The objective of the investigation was to explore the occurrence of YVX in yam from South America, and to study its genetic diversity compared to the only one YVX genome sequence available in the GenBank public database. Results: An initial investigation by HTS of bulked RNA extracts (n=23, combined into 4 pools) revealed occurrence of YVX only in samples collected in the region of Valença. Subsequent screening by RT-PCR of the individual samples composing the pool uncovered infection with YVX only in Discorea trifida. Total RNA extracts from three infected plants were individually sequenced, resulting in the assembly of three complete genome sequences of YVX, showing ~84% nucleotide identity to the reference sequence from Guadeloupe. Our results contribute to expanding the pool of sequences available for YVX, supporting detection purposes and stimulating additional investigations for future studies on YVX diversity and evolution.