بررسی گونه‌های فوزاریوم مولد پژمردگی و پوسیدگی ریشه نخود در استان لرستان

پوسیدگی ریشه و پژمردگی نخود از مخربت‌ترین بیماری‌های محدود کننده‌ی تولید نخود در استان لرستان محسوب می‌گردد. به منظور بررسی فوزاریوم‌های عامل پوسیدگی ریشه نخود، از مزارع نخود در استان لرستان بازدید به عمل آمد و تعداد 155 نمونه از بوته‌های مشکوک به بیماری و دارای علایم زردی و خشکی برگ‌ها و ساقه‌ها و برگچه‌های پایینی بوته‌ها، پژمردگی و پوسیدگی ریشه جمع‌آوری شد. سپس جداسازی، خالص‌سازی و شناسایی مشخصات ظاهری عامل مرتبط با هر نمونه در آزمایشگاه منطبق بر منابع معتبرانجام شد. آزمون بیماری‌زایی و سنجش توان بیماری‌زایی بر روی رقم حساس آرمان انجام شد. براساس خصوصیات ریخت‌شناسی و توالی‌یابی دو ناحیه ژنی فاصله‌ی ترانویس شده‌ی داخلی دی‌ان‌ای ریبوزومی (its) و ژن tef، در مجموع 77.4 درصد جدایه‌های قارچ فوزاریوم بیماری‌زا و 22.6 درصد جدایه‌های فوزاریوم غیر بیماری‌زا به شرح زیر جداسازی شد؛ در مجموع تعداد 53 جدایه به عنوان f. oxysporum، 43 جدایه f. solani، 37 جدایه f. redolans و 22 جدایهf. falciform شناسایی شدند. پس از شناسایی ریخت شناسی جدایه‌ها، یک جدایه از هر گونه به نمایندگی انتخاب و روابط فیلوژنتیکی آن‌ها مطالعه شد. همه‌ی جدایه‌های بیماری‌زا پس از مایه‌زنی روی رقم حساس آرمان ایجاد زردی و پژمردگی و پوسیدگی ریشه نمودند. نتایج این مطالعه نشان داد مهم‌ترین گونه بیماری‌زای در مزارع نخود استان لرستان گونه f. oxysporum f. sp. cicero می‌باشد. در آزمون بیماری‌زایی دامنه میزبانی جدایه‌های f. falciform، در گیاهچه‌های بامیه بیماری‌زا نبود، اما این جدایه‌ موجب پوسیدگی ریشه و زردی گیاهچه‌های ماش، عدس، گندم، جو، ذرت، لوبیا چشم بلبلی و گاودانه گردید. گونه‌ی f. falciform برای اولین بار از ایران روی ریشه نخود گزارش می‌گردد.

study of fusarium species causing wilt, and root rot in chickpeas in lorestan province

background and objectivesfusarium is a significant soil fungus found globally. the fungus responsible for the disease can survive as chlamydospores in infected seeds and plant debris for more than five years in the soil. when conditions are right, it can devastate entire crops. this fungus releases spores that grow when they come into contact with chemicals from the chickpea roots. the fungal threads invade the plant’s roots and vascular system, which blocks the plant’s ability to absorb water. as a result, the chickpea plant can die from lack of moisture. in iran, the disease is common in many areas where chickpeas are grown, resulting in a 17% decrease in chickpea yields. in lorestan province, it causes root rot and wilting in chickpeas, severely impacting their production. under suitable conditions, this disease can entirely devastate crops. to effectively manage this issue, it is crucial to identify the various fusarium species, understand their detrimental effects, and evaluate which plants they can infect. also, studying these species’ genetic relationships can facilitate the development of improved disease control strategies.materials and methodsthis study focused on identifying fusarium species that cause root rot in chickpeas in lorestan province. researchers visited chickpea farms, collecting 155 samples from plants exhibiting yellowing, wilting, and root rot symptoms. the samples underwent isolation, purification, and identification in the laboratory based on their morphological traits. pathogenicity tests were conducted on a susceptible chickpea cultivar named arman to evaluate the pathogenic potential of the identified fusarium species. this study focused on analyzing specific genetic markers to identify particular isolates. researchers amplified two gene regions: the internal transcribed spacer (its) of ribosomal dna and the ef1 α gene, utilizing materials from sinagen company. the amplified dna fragments were sequenced by biomegic company in tehran. the sequences were edited and analyzed using bioedit 7.1 software and registered in the ncbi genbank database. mega 7.0 software was employed for phylogenetic analysis to construct a phylogenetic tree, comparing the isolates with others in the gene bank. a bootstrap analysis with 1,000 repetitions was conducted to confirm the stability of the phylogenetic tree branches. the study evaluated specific isolates’ harmful effects on the above ground parts and roots of intentionally infected plants.resultsthe phylogenetic tree presented in this study, constructed from specific gene sequences, aligns with the results of morphological analyses. the research identified fusarium oxysporum and fusarium solani as the most prevalent isolates. f. falciforme affects plants by causing yellowing and wilting, starting from the lower leaflets and spreading upwards. the roots also show signs of damage, with visible root rot symptoms after emerging from the soil. additionally, there are instances of discoloration in the vascular bundles when looking at sections of the stem, both longitudinally and cross sectionally. these findings correspond with previous studies in the field. furthermore, the study uncovered that fusarium falciforme is a weak pathogen for chickpea roots. importantly, this research represents the first documented evidence of the pathogenic effects of fusarium falciforme on chickpeas.discussionthe phylogenetic tree presented in this study, constructed from specific gene sequences, aligns with the findings of morphological analyses. the research identified fusarium oxysporum and fusarium solani as the most prevalent isolates. the disease symptoms linked to most isolates from the f. oxysporum complex in this study resemble those caused by f. redolens. dna sequencing revealed that the f. oxysporum isolates are closely related to f. redolens, with a 96% genetic similarity. all isolates of f. redolens showed symptoms similar to those of f. oxysporum f. sp. ciceris in pathogenicity tests but without any color change in the vascular tissue. since black root rot is a localized issue, it is crucial to differentiate it from systemic diseases like wilting for effective plant pathology understanding. a combination of molecular analysis and thorough morphological examination is essential to identify these isolates correctly. these results are consistent with previous studies on the subject. furthermore, the investigation revealed that fusarium falciforme exhibits weak pathogenicity towards chickpea roots. importantly, this research represents the first documentation of the pathogenic effects of fusarium falciforme on chickpeas.