Fusarium culmorum: به عنوان یکی از گونه های بیماریزای پوسیدگی طوقه و ریشه کلزا در استان گلستان

Canola (Brassica napus L.) is a highly cultivated species, due to its high-quality oil content, high tolerance to salt stress, adaptability to various climates, the existence of spring and winter varieties, and diverse applications in the food, feed, and industrial sectors. Crown and root rot diseases represent a significant threat to global canola production, causing considerable economic losses annually. Various microorganisms contribute to the development of these diseases. The species of the genus Fusarium has been identified as a primary and particularly destructive pathogen responsible for crown and root rot diseases worldwide. This is due to the production of various mycotoxins and the resulting severe economic damage. To identify and evaluate the Fusarium isolates associated with crown and root rot of canola, 103 samples exhibiting symptoms were collected from canola fields in Golestan province during 1400-1402. The samples were transferred to the Genetics department and national plant gene bank of Iran, Seed and Plant Improvement Institute in Karaj in paper packets for further investigation. The crown and root sections were separated and washed under running tap water for 20 minutes. Subsequently, samples measuring 3–7 millimeters were excised from the interface between infected and healthy regions of the crown and root of each plant. The samples obtained from each plant were individually subjected to surface sterilization, then dried on sterile filter paper, and placed separately on potato dextrose agar (PDA) medium. Subsequently, the samples were incubated for 14 days at a temperature of 25±1 °C in an incubator. The purification of the Fusarium isolates was conducted using the single spore method on a water-agar medium. A total of 41 pure Fusarium isolates were obtained and identified as six distinct species. The isolates were identified as F. oxysporum, F. solani, F. culmorum, F. nygamai, F. graminearum, and F. acremonium based on microscopic (PDA culture) and macroscopic (CLA culture) characteristics. The identification key proposed by Leslie et al. (2006) was utilized. A disease assay was conducted in accordance with Koch's postulates in a greenhouse setting. Among the six identified species, F. culmorum exhibited the highest level of pathogenicity, with all isolates demonstrating pathogenic characteristics. Furthermore, molecular data obtained from the amplification of the target fragment of the Tri5 gene using specific primers Fc01F and Fc01R also confirmed the precise identification of F. culmorum. This species was identified as one of the primary causes of crown and root rot of canola in the analyzed samples obtained from the fields of Golestan Province. There is a report indicating that this species is responsible for the rot of rapeseed in Poland. As far as our finding this is the first instance of this species causing disease on Brassica napus in Iran.