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First report of orchid (Orchis laxiflora)
as a host of Sclerotinia minor, discovered in Turkey
C. Eken1*, E. Demirci1, A. Eşitken2
and S. Ercişli2
1 Department of Plant Protection, Faculty of
Agriculture, Atatürk University, 25240 Erzurum, Turkey
2 Department of Horticulture, Faculty of Agriculture,
Atatürk University, 25240 Erzurum, Turkey
* ceken@atauni.edu.tr
Accepted for publication 13/05/03
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Figure 1. Symptoms on Orchis laxiflora caused by Sclerotinia
minor.
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In Erzurum, Turkey, during June and
July of 2002, Orchis laxiflora Lam. Plants were affected by
a previously undescribed disease. Initial symptoms consisted of a
soft, watery rot at the crown and stem. Diseased tissue turned
black, extending along the stem, before plants wilted and
collapsed (Fig. 1).
The pathogen was isolated from symptomatic stem sections,
surface disinfected for 1 min in 0.5 % NaOCl, plated on potato
dextrose agar (PDA) and incubated at 25oC. The organism
isolated produced white mycelia and small (0.5 to 2.5 mm) black
sclerotia characteristic of Sclerotinia minor Jagger
(Pratt, 1993) (Fig. 2). This pathogen was consistently isolated
from these plants. Symptoms were reproduced in the greenhouse by
inoculating stems of 4-month-old plants with mycelial plugs (6 mm
diameter) from 5 day old PDA cultures. Inoculated plants were
enclosed in transparent plastic bags for 3 days. Control plants
were treated similarly, except that the agar disks did not contain
the fungus. All plants were incubated in a greenhouse at 21 to 23oC
with a 12h photoperiod. After 2 weeks, inoculated O. laxiflora
plants wilted and collapsed. S. minor was reisolated from
necrotic crown and stem tissues. No disease symptoms were observed
on uninoculated plants. The experiment was repeated and results
were similar to the first inoculations. S. minor causes
diseases on an extremely broad array of host plants worldwide. A
recent listing of hosts by Melzer et al. (1997) included 21
families, 66 genera, and 94 species. This is the first report of O.
laxiflora as a host of S. minor.
References
Melzer MS, Smith EA, Boland GJ, 1997. Index of plant hosts of Sclerotinia
minor. Canadian Journal of Plant Pathology 19, 272-80.
Pratt RG, 1993. Sclerotinia. In: Singleton LL, Mihail JD, Rush CM,
eds. Methods for Research on Soilborne Phytopathogenic Fungi.
St. Paul, MN, USA: APS Press, 74-78.
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Figure 2. Colony of Sclerotinia minor growing on PDA.
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