اولین گزارش بیماری پوسیدگی ریشه و طوقه توت‌فرنگی ناشی از Macrophomina phaseolina از ایران

Strawberry (Fragaria × ananassa Duchesne) is produced on 3500 ha in Iran. During surveys on strawberry root and crown rot disease (February-April 2007), a fungus resemble Macrophomina was isolated from crowns and roots of collapsed and dying strawberry plants which were collected from Golestan, Mazandaran and Kordestan provinces of Iran. To study rate of growth and cultural characteristic of isolates, a plug of each isolate was cultured on potato dextrose agar (PDA) (Merck) medium and incubated at 25ºC. After 6 days the fungal grew with dark oblong microsclerotia and filled 90 mm in diameter Petri plates. After 10 days ten microsclerotia were recovered from six colonies and ranged in size from 50 to 200 μm in length and 40 to 130 μm wide and were round to oblong or irregular in shape. This description matches that of Macrophomina phaseolina (Tassi) Goid (Holliday and Punithalingam 1970). Six representative isolates were used for a pathogenicity assay on nursery runner plants (cv. Camarosa) grown on perlite for 4 weeks in a greenhouse. Inoculum of M. phaseolina was produced by blending 2-week-old cultures on sand-perlite-Czapek-dox broth in Erlenmeyer flasks (250 ml) that were incubated at 25ºC. Each of six isolates was inoculated on four plants by adding 10 g of inoculum per pot (1 l). The plants were incubated at 26±2ºC with 12-h day/night conditions in a greenhouse. Sterile, sandperlite- Czapek-dox broth was applied in control pots. After 3 weeks 50 to 100% of inoculated plants developed wilting in one or more leaves. First mortality of plants was seen approximately 6 weeks after inoculation and 100% mortality was recorded after 10 weeks. Uninoculated plants remained symptomless. The pathogen was readily reisolated from inoculated plants. This fungus has been observed to cause disease in many plants (alfalfa, bean, corn, cotton, sunflower, sesame, soybean, olive) (Ershad, 2009) but to our knowledge, this is the first report of M. phaseolina crown and root rot of strawberry in Iran. Initial studies showed that these areas were infested with about 40-60% and approximately 1% of plants were infected in fields. Similarly, this pathogen has been reported from strawberry-growing areas of the United States of America, France, India, Spain and Israel (Mertely et al. 2005; Maas 1998; Avilés et al. 2008).