- Eola rasp leaf of cherry was first described by Milbrath and
Reynolds in Oregon in 1961. Dr. Cadman of the Scottish Horticultural
Research Institute suggested that this disease was incited by a strain
of tomato ringspot virus (TomRSV), but since then controversial results
with some isolates of EoIa rasp leaf have occurred in greenhouse
and serological tests. Since both tomato ringspot and tobacco ringspot
virus (TRSV) incited similar reactions on a number of host
plants, the possibility of TRSV being involved had been considered.
The object of this study was to identify the virus principally responsible
for Eola rasp leaf of cherry.
Twenty plant species were mechanically inoculated with six
isolates of EoIa rasp leaf virus (ERLV), TomRSV and TRSV to compare
symptoms. Among them, plant species that showed distinctive
symptoms to these viruses were Antirrhinum majus, Chenopodium amaranticolor, Datura stramonium, Glycine max, Petunia hybrida,
Pisum sativum, Phaseolus vulgaris and Vigna sinensis. Among the
isolates of ERLV, 16i incited symptoms closest to those incited by
TomRSV, while 17ao was apparently related to TRSV. The other isoIates of ERLV were closer to TomRSV than to TRSV, yet they incited
milder symptoms than those of either virus.
Tests on physical properties of these viruses demonstrated
that one ERLV isolate, 17ao, resembled TRSV and the others resembled
TomRSV. This was demonstrated most clearly in the longevity
in vitro tests. In the other two types of tests, four isolates of ERLV,
17a, 17o, 17r and 17v, were lower in thermal inactivation points and
lower in dilution end points than were TRSV and TomRSV. Since
TRSV inactivated at a higher temperature and withstood higher dilution
than TomRSV, these four isolates of ERLV would be closer to
TomRSV than to TRSV. Thermal inactivation and dilution end points
comparable to TRSV were demonstrated by 17ao, while these properties
for 16i were very close to those of TomRSV.
Cross-protection tests also demonstrated a relationship between
TomRSV and the majority of the ERLV isolates. Only one,
17ao, appeared to be related to TRSV. TomRSV isolate 51ad protected
petunia and Samsun tobacco from infection by TomRSV 51ad
and from five ERLV isolates, but not from the infection of TRSV 51ae
and ERLV isolate 17ao. TRSV isolate 51ae protected petunia and Samsun and Necrotic Turk tobacco from the infection of 17ao and 51ae,
but not from the other ERLV isolates and 51ad.
Serological test results supported the existence of a relationship
of five of the ERLV isolates to TomRSV; the other, 17ao, being
related to TRSV. In Ouchterlony agar double-diffusion tests, TomRSV
antisera and antisera obtained from rabbits injected with 16i and 17o
reacted with five ERLV isolates and TomRSV isolates, but not with
17ao and 51ae. TRSV antisera and antiserum obtained from a rabbit
injected with 17ao reacted with 17ao and 51ae from various sources
but not with the other ERLV isolates or TomRSV.
In conclusion, host range, symptoms, physical properties,
cross-protection and serology indicated that ERLV isolate 17ao was
a strain of TRSV, and the rest of the ERLV isolates were strains of