Apple chlorotic leafspot virus
R. M. Lister
Purdue University, Lafayette, Indiana, USA
Lister, Bancroft & Nadakavukaren (1965).
For disease description see
Luckwill & Campbell (1963).
- Pear ring pattern mosaic virus (Rev. appl. Mycol. 35: 831)
- Apple latent virus Type 1 (Rev. appl. Mycol. 45: 134)
An RNA-containing virus with very flexuous filamentous particles c. 600
x 12 nm. Found in woody rosaceous plants, including apple, pear, peach, plum,
cherry and apricot, from which it is sap-transmissible to a limited range of
herbaceous species. Natural mode of spread unknown; widespread and common in
vegetatively propagated commercial fruit tree clones, especially of apple, in
which it often causes no symptoms.
Causes a range of disease syndromes in some natural woody hosts, including
chlorotic leaf spot of Russian apple, line pattern of Malus platycarpa,
ring pattern mosaic of pear, dark green mottle of peach, and unnamed diseases of
quince and apricot. See
for an extensive review. The virus causes
no symptoms in commercial apples.
Reported from many countries. Probably occurs wherever apples are cultivated.
Host Range and Symptomatology
Outside the Rosaceae, the host range seems rather restricted (about 15 species
in 8 dicotyledonous families -
Lister et al., 1965
Saksena & Mink, 1969b
Grafting is used for transmission between
woody hosts. The virus is transmitted from woody to herbaceous hosts by inoculating
extracts from buds, young leaves, petals or fruits ground in a neutral buffer at
around 0.05 M. Additives such as 2% (v/v) nicotine base, or 2% (w/v) polyvinyl
pyrrolidone help but are not essential. Apple petals are a better source of virus
(Lister et al., 1965
and fruits may be also
- Malus sylvestris cv. R12740-7A (Russian apple). Chlorotic blotches,
usually distributed asymmetrically in young leaves: asymmetric leaf distortion
stunting of shoot growth.
- Malus platycarpa (Long Ashton clone). Irregular diffuse chlorotic ring
and line patterns in leaves, which are smaller than normal, distorted, and often
shed prematurely. Strains differ in virulence.
- For symptoms in other species and horticultural varieties of Malus and
woody Rosaceae, see
Luckwill & Campbell (1963)
- Chenopodium quinoa. After 3-6 days, large (2 mm diam.) etched primary
lesions, becoming pale brown and necrotic
Later, systemic chlorotic
spotting and mottling, with ring and line patterns, culminating in more general
chlorosis with necrosis
- C. amaranticolor. Symptoms are similar to those in C. quinoa, but
primary lesions tend to be compound, consisting of chlorotic spots surrounding
several necrotic dots.
- Phaseolus vulgaris cvs. Pinto, Bountiful, Kinghorn (bean). Purple-brown
necrotic spots or rings 1-3 mm in diameter. Not systemic.
- Virus transmissibility from C. quinoa to either C. quinoa or
P. vulgaris is improved by using clarified C. quinoa sap or
partially purified virus preparations
(Saksena & Mink, 1969a).
- C. quinoa is suitable for maintaining cultures and propagating virus for
- C. quinoa and P. vulgaris (see above).
Only a few isolates have been identified unequivocally by serology,
symptomatology in woody plants, and other properties. Isolates differ in virulence
towards herbaceous hosts, but not in their serological or physical properties.
Variants have been distinguished by symptomatology in woody hosts
Transmission by Vectors
Although spread in the field has been detected, the natural mode of spread is
unknown. A report of transmission by Eudorylamoid nematodes
(Fritzsche & Kegler, 1968
requires confirmation. The suggestion that spread may occur in pollination
Lister & Cadman, 1965
though not disproved, was based on an
erroneous identification of this virus with raspberry bushy dwarf virus (see
Transmission through Seed
Transmission by Dodder
Moderately antigenic, giving titres up to 1/512. Ring-precipitin tests can
be used with sufficiently purified virus, including virus concentrated from apple
(Saksena & Mink, 1969c
Latex flocculation tests give specific
positive results with crude buffered extracts from infected C. quinoa
or apple petals, but not apple leaves or fruits; and gel-diffusion tests work with
virus fragments or virus protein, but not with intact virus
(Lister & Hadidi, unpublished).
No serological differences have been found between strains. The virus seems
unrelated in serological and plant protection tests to the morphologically similar
apple stem grooving virus
but its behaviour in plant protection tests may be
(Van der Meer, 1968
A suspected relationship to
raspberry bushy dwarf virus
is now disproved
(Barnett & Murant, 1970
Stability in Sap
Much less stable than
apple stem grooving virus
in plant extracts. In
bentonite-clarified C. quinoa
sap (see Purification), thermal inactivation point
(10 min) is 52-55°C, half-life at 45°C is 12±1 min and dilution
end-point is c.
; infectivity is abolished in 1 day at
20°C and in c.
10 days at 4°C. Infectivity is inhibited by crude
(Saksena & Mink, 1969a
the inhibitor may be a
ribonuclease (Lister & Hadidi, unpublished).
The most satisfactory method depends on clarifying extracts with bentonite
Lister et al., 1965
Lister & Hadidi (unpublished)
obtained no improvement using magnesium bentonite (recommended by
Saksena & Mink, 1969b
they developed the following method, based on that of
de Sequeira & Lister (1969)
Blend each 100 g infected C. quinoa leaf in 200 ml 0.01 M Tris-HCl buffer
(pH 7.6), containing 0.01 M MgSO4. Squeeze through cheesecloth and then
thoroughly clarify by cautiously adding bentonite suspension (c. 40 mg/ml in
0.01 M phosphate buffer at pH 7-8). Centrifuge at low speed. Precipitate the virus
from the supernatant fluid by adding polyethylene glycol, M. Wt 6000, to 8% (w/v),
and allow to stand for 1 hr. Centrifuge at low speed and resuspend virus pellets in
Tris-HCl buffer. Concentrate by ultracentrifugation. Purify the virus further by
density gradient centrifugation. Do all steps at c. 4°C.
Yields are 1-2 mg/100 g of leaf, depending on the strain.
Properties of Particles
Sedimentation coefficient (s20,w
): about 96 S (not
corrected to infinite dilution). No accessory virus particles detected.
Electrophoretic mobility: -5.1 x 10-5 cm2 sec-1
volt-1 in 0.05 M Tris/0.005 M MgCl2 buffered to pH 7.5 in 3%
sucrose (determined by electrophoresis in a sucrose gradient).
A260/A280: 1.18, according to
Saksena & Mink (1969b);
& Hadidi (unpublished) could not confirm this but obtained values, for very
pure preparations, of 1.85 falling to 1.55 on dialysis, which can cause particle
A very flexuous filament with obvious cross-banding and helical symmetry
600 nm; width c.
12 nm; pitch of helix c.
nm. Particle fragments viewed end-on show a hollow centre, but this is not
visible laterally. Best stains for electron microscopy are uranyl acetate or uranyl
formate; breakage occurs in phosphotungstate
(Lister et al., 1965
In the absence of certain divalent cations or polyamines, particles degrade,
forming fragments sedimenting at about 17 S (Lister & Hadidi, unpublished).
Contains RNA (Lister & Hadidi, unpublished).
Relations with Cells and Tissues
Unknown: has been eliminated from some apple varieties and rootstocks by heat
therapy (37°C for up to 3 weeks).
Lister, Bancroft & Shay (1964)
reported isolates of
apple chlorotic leaf spot virus that specifically caused a chlorotic leaf spot
disease in Russian apple R12740-7A. These and some other isolates have been shown,
by detailed serological and other tests, to be related. However, for many assumed
isolates, critical comparisons have not been made. Because strains differ in the
symptoms they cause in both woody and herbaceous indicators, serological and/or
thorough property testing is essential for accurate diagnosis.
- Barnett & Murant, Ann. appl. Biol. 65: 435, 1970.
- Cadman, Pl. Dis. Reptr 47: 459, 1963.
- Cadman, Pl. Dis. Reptr 49: 230, 1965.
- Cropley, Pl. Dis. Reptr 47: 165, 1963.
- Cropley, Pl. Dis. Reptr 48: 678, 1964.
- Cropley, Ann. appl. Biol. 61: 361, 1968.
- Cropley, In Tech. Commun. Commonw. Bur. Hort. Plantn Crops 30, Suppl.2/3/4: 10, 1969.
- de Sequeira & Lister, Phytopathology 59: 1740, 1969.
- Fritzsche & Kegler, TagBer. dt. Akad. Landw Wiss. Berl. 97: 289, 1968.
- Lister, Bancroft & Shay, Phytopathology 54: 1300, 1964.
- Lister, Bancroft & Nadakavukaren, Phytopathology 55: 859, 1965.
- Lister & Cadman, Zast. Bilja 16: 233, 1965.
- Luckwill & Campbell, In Tech. Commun. Commonw. Bur. Hort. Plantn Crops 30: 5, 1963.
- Nemec, Pl. Dis. Reptr 51: 283, 1967.
- Saksena & Mink, Phytopathology 59: 61, 1969a.
- Saksena & Mink, Phytopathology 59: 84, 1969b.
- Saksena & Mink, Phytopathology 59: 877, 1969c.
- Van der Meer, TagBer. dt. Akad. Landw Wiss. Berl. 97: 27, 1968.
Photographs: courtesy of Purdue Agricultural Experiment Station.
Chlorotic leaf spot disease in Russian apple R12740-7A, showing chlorotic
blotches and asymmetric distortion.
Inoculated leaf of Chenopodium quinoa showing necrotic lesions.
Systemic chlorotic and necrotic spotting in C. quinoa.
Particles of apple chlorotic leaf spot virus in uranyl formate. Note
cross-banding and fragments (discs) showing hollow centre. Bar represents 100 nm.