Abstract
In Erzurum, Turkey, during June–July, 2002, Orchis laxiflora was 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. The pathogen was isolated from affected stem sections, surface-disinfected for 1 min in a solution of NaOCl, producing 0·5% available Cl2, plated on potato dextrose agar (PDA) and incubated at 25°C. The organism isolated produced white mycelia and small (0·5–2·5 mm) black sclerotia characteristic of Sclerotinia minor (Pratt, 1993). This pathogen was consistently isolated from these plants. Symptoms were reproduced in the glasshouse 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 glasshouse at 21–23°C with a 12-h 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 series of inoculations. Sclerotinia minor causes diseases on an extremely broad range 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.
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