Published Date: 2003-06-26 23:50:00
Subject: PRO/PL> Colletotrichum gloeosporioides, citrus - Morocco
Archive Number: 20030626.1575

COLLETOTRICHUM GLOEOSPORIOIDES, CITRUS - MOROCCO
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Date: 26 June 2003
From: ProMED-mail<promed@promedmail.org>
Source: British Society Plant Pathology, NEW DISEASE REPORTS, Vol. 7[edited]

First report of _Colletotrichum gloeosporioides_ causing withertip on twigs
and tear stain on fruit of citrus in Morocco
H Benyahia <hamidbenyahia2002@yahoo.fr> (National Institute of Agronomic
Research, Laboratory of Citrus improvement and Biotechnology, Kenitra, BP
1055, Morocco; A Jrifi, C Smaili (Laboratory of Zoology, INRA Kenitra,
Morocco; and M Afellah and LW Timmer (University of Florida, CREC 700,
Experiment Station Rd., Lake Alfred, FL 33850. Accepted for publication
16/04/03
Citrus trees (_Citrus sinensis_ L. Osbeck), but not lime ( _C.
aurantiifolia_) were observed in Morocco expressing symptoms resembling
withertip on twigs and tear stain on fruits. Dieback often progressed
slowly and caused leaves to wilt, turn yellow and drop off. Twigs and
branches appeared as if scorched by fire. When twigs were dry, minute
brown-to-black, slightly raised, clumped pustules were observed. Under
humid conditions, a pink slimy material appeared on dead bark and twigs.
This symptom also occurred on seedlings of citrus rootstocks in greenhouses
in Morocco. Affected fruit showed tear stain symptoms, (Fawcett (1936).
Symptoms were superficial on unbroken peel and formed dull red to dull
reddish-green streaks or bands down the fruit, occasionally covering much
of the fruit surface. On late season, overripe fruit, streaks sometimes
became brownish in colour, resembling rust mite damage.
To clarify the etiology of the disease, symptomatic twigs and fruit were
collected from a grove in the Gharb region. Affected twigs and fruit were
washed, swabbed with ethanol and dried. Twig sections (10 cm) were placed
on moist paper in a Petri plate. Pieces of peel, 5 mm in diameter, were
plated on PDA in alternating light and dark at 25°C. Pink slimy masses
developed from black spots observed on dead twigs and from incubated fruit
peel.
After plating onto PDA, a white mycelial growth was observed, along with
the production of numerous salmon pink spore masses without setae and
conidia that rounded ends. The growth medium turned orange. Growth of these
isolates was almost completely inhibited on media containing 1 m g/ml of
benomyl which is characteristic of _Colletotrichum gloeosporioides_ [Cg]
(Peres, et. al, 2003).
Both Cg and _C. acutatum_ have been reported on citrus (Timmer et al.,
2000). However, _C. acutatum_ only causes postbloom fruit drop of sweet
orange and anthracnose of lime. Also this species produces conidia with at
least 1 end fusiforme and all isolates should be inhibited only by ~50
percent on media with 1 m g/ml of benomyl (Peres et al., 2003). Only Cg was
reported to cause withertip and tear stain of citrus (Klotz, 1961).
Cg is confirmed as the pathogen causing these symptoms on _C. sinensis_ in
Morocco. Pathogenicity was confirmed using Koch's postulates, with
inoculations made on excised twigs, intact plants of Troyer citrange
(_Poncirus trifoliata_ x _C. sinensis) and on fruit, using isolated spores.
After incubation, tear stain and withertip symptoms developed on fruit and
excised twigs/seedlings, respectively. Cg was reisolated from excised
twigs, fruits and plants.
This is the first report of withertip and tear stain caused by Cg in Morocco.
References
Fawcett HS, 1936. Citrus Diseases and Their Control. New York, USA: McGraw
Hill Book Co.
Klotz J, 1961. Color Handbook of Citrus Diseases. California, USA:
University of California.
Peres NAR, Souza NL, Peever TL, Timmer LW, In Press. Benomyl sensitivity of
isolates of Colletotrichum acutatum and C. gloeosporioides from citrus.
Plant Disease
Timmer, LW, Garnsey, SM, Graham, JH, eds, 2000. Compendium of Citrus
Diseases, 2nd ed. St. Paul, MN, USA: APS Press Inc.
--
ProMED-mail
promed@promedmail.org
[Cg is a fungal pathogen that infects a range of food crops, including
citrus fruits, mango, papaya, banana and avocado. Weathertip (die back)
directly affects shoot tips, causing necrosis and reductions in fruit
yield. -Mod.DH]
........................dh/mpp

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