Two double-stranded ribonucleic acid (dsRNA) elements were detected
in
an isolate of the clavicipitaceous grass endophyte Epichloë
festucae obtained from an asymptomatic Festuca rubra plant.
No dsRNA was detected in three other isolates of E. festucae.
The size of
the two dsRNA elements isolated from mycelium was of 5·2 and 3·2
kbp.
Hybridization experiments with a cDNA probe
complementary to the 5·2 kbp dsRNA showed that there was no sequence
similarity between the dsRNA elements. Isometric virus-like particles of
about
50 nm in diameter were observed by electron microscopy in sucrose-gradient
purified virus preparations from
the isolate containing dsRNA. The 5·2 kbp dsRNA element was
present in the partially purified virus preparations, suggesting that
this element is encapsidated. There was no difference with respect to
growth rate or colony morphology between the dsRNA
containing and dsRNA-free isolates. The presence of dsRNA and virus-like
particles suggests the presence of a mycovirus in the
Vit5 strain of E. festucae.