New disease of tomato in Israel caused
by a strain of Tomato apical stunt pospiviroid
Addition to the EPPO Alert List
In spring and summer 1999 and 2000,
tomato plants showing stunting, leaf deformation, yellowing, and
brittleness were observed in a few commercial plastic houses at
different locations in the coastal region of Israel. Fruits were
considerably reduced in size with a pale red discoloration. In
all cases, the disease spread rapidly mainly along plant rows,
resulting in a disease incidence of nearly 100 percent and heavy
yield losses. Molecular assays revealed the presence of Tomato
apical stunt pospiviroid (TASVd) in diseased tomato plants.
TASVd was first found and characterized
in Ivory Coast, but no data was given on its epidemiology or
economic impact. Another strain was found in Indonesia, but
again without data on potential economic impact. Cloning and
sequencing of viroid RNA showed that the Israeli strain has 92
percent identity with the type strain (Ivory Coast) and 99
percent with the Indonesian strain. The experimental host range
and symptomatology of the Israeli strain also differed from
those of the type stain. Under experimental conditions, the
Israeli strain of TASVd was readily transmitted from infected to
healthy tomato plants by grafting or mechanical inoculation.
Further studies are needed on possible pollen or seed
transmission.
Tomato apical stunt pospiviroid (a new
disease of tomato) Tomato apical stunt pospiviroid (TASVd) came
to our attention because it is reported as a new and serious
disease of tomatoes in Israel.
Found in Israel (on tomatoes
_Lycopersicon esculentum_ grown under plastic houses in the
coastal region). TASVd was first described in Ivory Coast, and
another strain was reported from Indonesia. However, data is
lacking on the extent, severity, and economic impact of the
diseases it may cause. Data on its host range is lacking.
Affected tomato plants in Israel showed shortened internodes
(bushy appearance), leaf deformation and yellowing, reduced
fruit size, and pale red discoloration of fruit. Up to 100
percent disease incidence could be observed with heavy yield
losses.
Transmission is by grafting from
infected to healthy tomato plants or by mechanical inoculation
(in experimental conditions). No data on pollen or seed
transmission.
Common route of infection is by planting
of tomatoes, fruits? obtained from countries where TASVd occurs.
Tomato is an important crop in the EPPO region, both indoors and
outdoors. Data is lacking on geographical distribution, host
range, and epidemiology of TASVd. Control of viroids is
difficult in practice, and it would be desirable to avoid any
further spread of a potentially serious disease of tomatoes.
Source(s)
Antignus, Y.; Lachman, O.; Pearlsmand, M.; Gofman, R.;
Bar-Joseph, M. (2002) A new disease of greenhouse tomatoes in
Israel caused by a distinct strain to Tomato apical stunt viroid
(TASVd). Phytoparasitica, 30(5), 502-510.
[There are 2 known TASVd strains
infecting tomato: the type strain (TASVd-Ivory Coast) and one
from Indonesia. Both cause significant crop loss. The genomes of
the 2 viroids are very similar (99.7 percent identity) despite
their distant geographic origins. A third strain, isolated from
_Solanum pseudocapsicum_ [Jeusalem cherry], does not occur
naturally in tomato but can infect tomato by mechanical
inoculation.
