Resumo

SANDOVAL, María C; NOELTING, María CI  e  CRISTOBAL, Eva H. FIRST REPORT OF Colletotrichum gloesporioides CAUSING DIE BACK IN Rosmarinum officinalis L. IN BUENOS AIRES, ARGENTINA. Rev. Protección Veg. [online]. 2008, vol.23, n.1, pp. 54-58. ISSN 2224-4697.

Cultivation of the shrub Rosmarinum officinalis L. is of great interest due to its aromatic and medicinal properties. In 2004, in the south of Buenos Aires province (Argentina), rosemary plants showing wilt and necrotic lesions in leaves, stems and twigs (die back) were observed in the field and the greenhouse. This work has focused on the identification of the causal agent of the above mentioned pathology. Forty plants were examined and segments of the symptomatic tissues from ten of them were disinfected with a 2% sodium hypochlorite solution, rinsed in sterile water and plated into Petri dishes with potato dextrose agar (PDA, 2%). The plates were incubated at 22ºC for eight days. Grayish white colonies and acervuli with conidia in orange masses and dark setae were observed on the all tissue segments. The cylindrical shaped conidia germinated developing mycelium or apressoria. The isolate was identified as Colletotrichum gloesporioides (Penz) Penz & Sacc. To confirm its pathogenicity, leaves and twigs taken from ten healthy plants were inoculated with a suspension of the fungus using a hypodermic syringe, the control was inoculated with sterile distilled water. This material was cultured in Petri dishes with PGA. This test reproduced the symptoms observed in the field and greenhouse. Between 24_48 h after inoculation, all the tissues developed necrosis. The pathogen was then reisolated from leaves and twigs fulfilling Koch´s postulates. The controls remained symptomless. This is the first report of Colletotrichum gloesporioides as the causal agent of die back in Rosmarinum officinalis in Argentina.

Palavras-chave : rosemary; Colletotrichum gloesporioides; die back; aromatic-medicinal; Lamiaceae.

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