شناسایی گونه‌های قارچی عامل بیماری‌های تنه‌ی تاک در استان فارس

به منظور شناسایی گونه‌ های قارچی عامل بیماری های تنه ی تاک در استان فارس، در ماه‌ های اردیبهشت تا شهریور 1397 تا 1399 از درختچه‌ های بالغ تاک که علائم کاهش رشد، زردی و سرخشکیدگی را در بخش های هوایی وتغییر رنگ بافت چوبی را در برش تنه نشان می دادند نمونه‌ برداری شد. قطعات کوچکی از مرز مناطق تغییر رنگ یافته و بافت نسبتاً سالم چوب جدا و پس از سترون سازی به تشتک های حاوی محیط کشت منتقل شدند. جدایه های قارچی پس از رشد به روش نوک‌ ریسه و یا تک اسپور خالص‌ سازی شدند. شناسایی جدایه ها با استفاده از ویژگی های ریخت‌شناختی و توالی سنجی نواحی مختلف ژنی انجام شد. در مجموع 166 جدایه‌ ی قارچی شامل گونه‌ های botryosphaeria dothidea، cytospora chrysosperma، fomitiporia mediterranea، kalmusia variispora، macrophomina phaseolina، phaeoacremonium minimum و phaeoacremonium parasiticum شناسایی شد. گونه‌ های c.  chrysosperma و p. minimum با فراوانی 5.42% و 28.31% به ترتیب کم‌ترین و بیش‌ ترین فراوانی را در میان جدایه‌ ها به خود اختصاص دادند. آزمون بیماری زایی روی نهال های یک ساله ی تاک در گلخانه نشان داد همه گونه‌ ها قادر به ایجاد بیماری در گیاهان مایه زنی شده هستند. به منظور تکمیل اصول کخ، قارچ های عامل بیماری مجدداً از گیاهان مایه زنی شده جداسازی و با استفاده از خصوصیات ریخت‌ شناختی و مولکولی شناسایی شدند. تمامی گونه های فوق به استثنای p. minimum و p. parasiticum برای نخستین بار از تاک‌ های آلوده به بیماری های تنه در استان فارس گزارش می‌ شوند.

Identification of fungal causal agents of grapevine trunk diseases in Fars province

Background and ObjectivesGrapevine trunk diseases are destructive fungal diseases that have considerably increased in the recent decades worldwide. More than 130 fungal species were associated with grapevine trunk diseases worldwide; however, the pathogenicity tests have not been conducted for some fungal species. From 2018 to 2020, grapevines with stunted growth, yellowing, branch dieback, and discoloration of the wood tissues symptoms were observed during field observation in the Fars province of Iran. This study aims to isolate, identify and characterize the fungal agents that cause these diseases using a combination of the morphological and molecular approaches.Materials and MethodsGrapevines with stunted growth, yellowing, branch dieback, and discoloration of the wood tissues symptoms were used for the isolation of fungal strains. Small pieces of infected wood tissues taken from the margin of symptomatic and approximately healthy parts were surface sterilized and plated onto potato dextrose agar and malt extract agar media amended with ampicillin. Fungal colonies were purified using single spore and hyphal tip methods. Isolates were identified using morphological characteristics as well as sequencing of different gene regions. The pathogenicity of the isolates was tested in greenhouse conditions using oneyearold seedlings of grapevine. To complete Koch’s Postulates, fungal agents were reisolated from inoculated plants and identified.Results166 fungal isolates were obtained and identified using the morphological characteristics as well as sequencing of different gene regions. The isolates were identified as Botryosphaeria dothidea, Cytospora chrysosperma, Fomitiporia mediterranea, Kalmusia variispora, Macrophomina phaseolina, Phaeoacremonium minimum, and Phaeoacremonium parasiticum. Among the species, P. minimum (28.31%) and C. chrysosperma (5.42%) had the most and least frequency, respectively. Pathogenicity tests using oneyearold seedlings in glasshouse showed all tested isolates can cause grapevine trunk diseases and produced white rot (in F. mediterranea) or wood necrosis (in other species) on inoculated tissue, developing from the point of inoculation. DiscussionThis study’s results showed that grapevines in Fars province are infected with fungi causing trunk diseases, which were previously reported from other provinces of Iran and other countries. According to our knowledge, it is the first report of all species, except P. minimum and P. parasiticum, causing grapevine trunk diseases in Fars province. More studies are required to better understand the causal agents of grapevine trunk diseases in other parts of Iran and introduce chemical or natural components that can reduce the economic losses caused by grapevine trunk diseases.