بیماری لکه قهوه‌ای (سوختگی ریزوکتونیایی) النا در مازندران

نویسنده

• محمد علی آقاجانی

استادیار پژوهش، بخش تحقیقات گیاه‌پزشکی، مرکز تحقیقات کشاورزی و منابع طبیعی استان گلستان، گرگان، ایران.

چکیده

در تابستان 1377 و 78، در یک باغ مرکبات واقع در منطقه بابل­کنار در جنوب شهرستان بابل، علایم بیماری لکه قهوه­ای یا سوختگی ریزوکتونیایی بر روی یک گراس وحشی به نام اِلنا یا ارزن جنگلی (Oplismenus hirtellus) مشاهده گردید. علایم بیماری شامل لکه­های تقریباً مدور با قطر متوسط 20 تا 100 سانتی­متر بود که در آن لکه، تمام گیاهان موجود پس از نشان دادن لکه­های سوخته کوچک روی برگ و غلاف، به­گونه کامل سوخته و خشکیده شده، سختیه­های قهوه­ای تیره رنگ قارچ به فراوانی روی بافت­های سالم و سوخته و خاک تشکیل گردید. گیاهان در اواخر تابستان با سرد شدن هوا از مرکز لکه شروع به بهبود کردند و یک الگوی حلقوی ایجاد کردند. در تمام جداسازی­ها، یک ریزوکتونیای چندهسته­ای از بافت­های سوخته جدا شد. بر اساس ویژگی­های پرگنه و میلسیوم، قارچ به عنوان Rhizoctonia solani شناسایی شد و گروه آناستوموزی آن AG 1 تعیین گردید. بر اساس ویژگی­های کشت سختینه، زیرگروه جدایه­ها به عنوان AG 1- IA تعیین شد. قطر متوسط ریسه 7 میکرومتر و تعداد متوسط هسته­ها در هر سلول ریسه­ای 4/6 عدد بود. پرگنه­ی قارچ بعد از دو هفته رشد روی محیط کشت سیب زمینی، دکستروز آگار (PDA) قهوه­ای روشن بود و تعداد زیادی سختینه­ی قهوه­ای تیره با ابعاد
7/0-4 × 1-5/4 میلی­متر روی محیط کشت تولید شد. درجه حرارت بهینه آن برای رشد 28 و دماهای کمینه و بیشینه به ترتیب 10 و 35 درجه سانتی­گراد بود. نرخ رشد خطی قارچ در دمای بهینه 34 میلی­متر در روز بود. بیماری­زایی قارچ با قرار دادن قرص­های 8 میلی­متری از حاشیه پرگنه بر روی برگ­ها و غلاف­های گیاهان و تولید علایم سوختگی به اثبات رسید و قارچ مجدداً از بافت­های بیمار جدا گردید. این نخستین گزارش از وجود بیماری لکه قهوه­ای (سوختگی ریزوکتونیایی) چمن‌ها در ایران می­باشد و گیاه النا به عنوان میزبان جدیدی برای قارچ R. solani در ایران معرفی می­گردد.

کلیدواژه‌ها

• النا
• Oplismenus hirtellus
• ریزوکتونیا
• Rhizoctonia solani AG 1-IA
• سوختگی ریزوکتونیایی

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عنوان مقاله [English]

Brown patch (Rhizoctonia blight) of bristle basket grass in Mazandazan, Iran

نویسنده [English]

• M.A Aghajani

چکیده [English]

"> The symptoms of brown patch or Rhizoctonia blight of bristle basket grass (Oplismenus
hirtellus) were observed in the summer of 2004 in a citrus orchard in Babolkenar region,
South of Babol, Mazandaran province. The individual plant symptoms consisted of blighted
spots, which gradually expanded to encompass the entire surface of the leaf. Patches of
affected grass had a diameter of approximately 20 to 100 cm. Dark brown sclerotia were
abundantly produced on the diseased plants and in soil.Plants started to recover and resumed
growth from the centre of the patch outward at the end of summer (because of the cooling of
the air), producing a ring pattern in the affected area. A multinucleate Rhizoctonia sp. was
consistently isolated from blighted tissues. Based on colony and mycelial characteristics, the
fungus was identified as Rhizoctonia solani, and the anastomosis group (AG) for most of
these isolates was determined as AG 1 by anastomosis testing. On the basis of cultural and
sclerotial characteristics, subset of the isolates was determined as AG 1- IA. The hyphal
diameter of the isolates was 7.0 5m, and the mean number of nuclei was 6.4 per hyphal cell.
The colony was light brown on potato dextrose agar after 2 weeks of growth, and dark brown
sclerotia measuring 0.7 to 4 × 1 to 4.5 mm were abundantly produced on the medium.
Cardinal temperatures for growth of this isolate were 10, 28, and 35°C. The linear growth rate
at the optimum temperature was 34 mm per day. Pathogenicity of the AG 1-IA isolate was
confirmed by placing 8-mm disks from the margins of an actively growing colony on the
leaves and sheaths of the host plant. Symptoms observed were the same as those in the field,
and the fungus was reisolated from the blighted tissue. To our knowledge, this is the first
report on the occurrence of brown patch disease of O. hirtellus in Iran. The bristle basket
grass is introduced as a new host for R. soloni in Iran.

کلیدواژه‌ها [English]

• bristle basket grass
• Oplismenus hirtellus
• Brown patch
• Rhizoctonia blight
• Rhizoctonia solni
• AG1-IA

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