نوع مقاله : مقاله پژوهشی
نویسندگان
1 گروه گیاهپزشکی دانشکده کشاورزی، دانشگاه جیرفت، جیرفت، ایران.
2 بخش تحقیقات گیاهپزشکی، مرکز تحقیقات و آموزش کشاورزی و منابع طبیعی هرمزگان، سازمان تحقیقات و آموزش کشاورزی، بندرعباس، ایران
چکیده
کلیدواژه‌ها
عنوان مقاله [English]
نویسندگان [English]
Root and crown rot is a common tomato disease in the major production areas of Hormozgan province. The present study was conducted to isolate, identify, and determine the frequency of fungal agents associated with tomato root and crown rot in Hormozgan province. In total, 984 fungal isolates were obtained from tomato plants with yellowing, wilting, and root and crown rot symptoms. Identification of the isolates was done based on the morphological characteristics and the comparison of the obtained sequences of the ribosomal internal transcribed spacer region (ITS-rDNA) and parts of the translation elongation factor-1 alpha (tef1-α) gene with relevant sequences available in GenBank. According to the results, the highest frequency belonged to Fusarium oxysporum isolates (73%), and afterward to Rhizoctonia solani and F. acutatum species with eight and one percent frequencies, respectively. The results of the pathogenicity tests of the fungal species on tomato seedlings hybrid Sunseed 6189 at the stage of four true-leaves revealed that all three species were pathogenic on tomato seedlings and caused root and crown rot, yellowing, and death of the plant aerial tissues. Pathogenic isolates of F. oxysporum were identified as F. oxysporum f. sp. radicis-lycopersici using sprl-specific primers. To the best of our knowledge, this is the first report of F. oxysporum f. sp. radicis-lycopersici on tomato in Hormozgan province, and the first report of F. acutatum as tomato root and crown rot agent in the world.
کلیدواژه‌ها [English]
Extended Abstract
Introduction
Tomato root and crown rot constitute a prevalent and devastating disease in the primary tomato-producing regions of Hormozgan province. Afflicting tomato plants from their initial seedling stage through to maturity, the disease exhibits various symptoms, including root and crown necrosis, loss of hairy roots, discoloration in the vascular system of the crown and basal stem, wilting, yellowing, necrosis of older leaves and petioles, reduced fruit quantity and quality, and eventual plant death. In Iran, a variety of fungal and oomycota species, such as Fusarium solani, F. oxysporum, F. equiseti, F. acuminatum, F. proliferatum, F. laterinum, F. semitectum, F. pseudoanthophilum, Rhizoctonia solani, Macrophomina phaseolina, Verticillium dahliae, Phytophthora capsici, P. drechsleri, P. nicotianae, and P. aphanidermatum, have been identified as agents responsible for causing tomato root and crown rot. This study aims to isolate, identify, and determine the prevalence of fungal agents contributing to tomato root and crown rot in Hormozgan province, located in southern Iran.
Materials and Methods
During the years 2021 and 2022, tomato plants displaying symptoms such as yellowing, wilting, and root and crown rot were systematically collected from eight distinct regions within Hormozgan province—Isin, Dargir, Kahurestan, Parsian, Hashtbandi, Rudan, Rezvan, and Ghazi Qala. Subsequently, root and crown tissue pieces underwent surface disinfection, were transferred onto a PDA medium, and were incubated at 25±1 °C for 10 days. Identification of the fungal isolates relied on morphological characteristics and the comparative analysis of the nucleotide sequence of the ribosomal internal transcribed spacer region (ITS-rDNA) and segments of the translation elongation factor-1 alpha (tef1-α) gene. To fulfill Koch’s postulates, the pathogenicity of selected isolates was tested on tomato seedlings (hybrid Sunseed 6189) at the four true leaves stage, under greenhouse conditions.
Results and Discussion
A total of 813 fungal isolates were obtained from symptomatic tomato plants. The predominant frequency was attributed to F. oxysporum isolates (73%), with R. solani and F. acutatum species being isolated at frequencies of eight and one percent, respectively. Pathogenicity tests confirmed the ability of all species to induce root and crown rot, yellowing, and eventual plant death in tomato seedlings. F. oxysporum pathogenic isolates were specifically identified as F. oxysporum f. sp. radicis-lycopersici using sprl-specific primers. This study represents the initial documentation of F. oxysporum f. sp. radicis-lycopersici on tomatoes in Hormozgan province and the first-ever report of F. acutatum as a causative agent of tomato root and crown rot globally.
Conclusion
The findings of this investigation, involving the isolation of fungal species from the root and crown of symptomatic tomato plants and the confirmation of their pathogenicity, underscore the role of soil-borne fungi, particularly F. oxysporum f. sp. radicis-lycopersici, in the initiation of root and crown rot on tomato in Hormozgan province. Recommendations for disease management in affected areas include the adoption of resistant cultivars, the cultivation of disease-free seedlings, optimal irrigation and nutrition practices, and effective environmental stress management. Future studies are proposed to assess the resistance of prevalent tomato cultivars in these regions against F. oxysporum f. sp. radicis-lycopersici.
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