Resumen

SALAZAR, Luis; DIAMONT, Diego  y  APONTE, Glenda. Identification of the causing agent of Stevia rebaudiana  wilt in samples from Aragua State, Venezuela. Bioagro [online]. 2015, vol.27, n.1, pp.57-61. ISSN 1316-3361.

Two samples of Stevia rebaudiana, presenting upward necrotic wilt in the stem, were brought to the diagnostic service for phytopathogen-produced diseases of INIA-CENIAP, en Maracay, Venezuela. This species has been introduced in the country due to its potential as a sweetener. The pathogen was isolated by direct seeding, which consisted in separating each plant organ, disinfecting them with 2 % NaClO, and placed in potato dextrose agar culture medium (PDA, with streptomycin), under conditions of isolation chamber; tissue was incubated at 28 °C / 48 h. Then, typical colonies were isolated on PDA with streptomycin. After obtaining pure cultures, we proceeded with Koch's postulates. For inoculation 60-days old Stevia plants, grown in sterile substrate, were used. Plants were inoculated by infiltration using a suspension of 1x10⁶ conidia of the pathogen per mL. Inoculated plants were placed in a wet chamber and daily observations were made until symptoms onset. Fungus was reisolated and macro and microscopic aspects of the fungus were characterized. Identification of the pathogen was achieved by using a taxonomic identification key. White colonies were observed which later became purple. Microscopic structures such as conidia, chlamydospores and macroconidia were also observed. The pathogenicity test demonstrated that the fungus Fusarium oxysporum was causing of the disease in Stevia plants.

Palabras clave : Fusarium; isolates; pathogen.

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