Mycobiota associated with a disease in plants of Lavandula hybrida Reverchon

摘要

The lavendin (Lavandula hybrida Reverchon) and the lavender (Lavandula officinalis Chaix ex Villars) are used in the pharmaceutical, cosmetic, and veterinary industries. The lavendin is the species with the most extended production area for its high yield of good quality essential oil and dried flowers. In 2012, in the south of Buenos Aires province (Argentina), L.hybrida plants with dark and necrotic lesions on leaves and stems, with death of the most affected plants, were observed in the field. This problem justified the present study to identify the cause of the damage observed. Segments of symptomatic tissues of twenty plants, chosen from a total of forty plants examined, were disinfected and placed into Petri dishes with potato dextrose agar (APG 2%). Fungal colonies developed on all the tissue segments.The isolates were identified as Phomopsis lavandulae (Gabotto) Cif. & Vegni), Fusarium oxysporum Schltdl, Selenophoma Maire, and Pestalotiopsis maculans (Corda) Nag Raj.Pathogenecity of each fungus was separately examined by inoculating leaves and stem of ten healthy plants with the fungal suspension using a hypodermic syringe; the control was inoculated with sterile distilled water. This material was cultured in Petri dishes with PGA. In this test, only the material inoculated with Selenophom reproduced the symptoms observed in the field. Between 24-48 h after inoculation, all the tissues developed browning and necrosis. The pathogen was then reisolated from leaves and stems fulfilling Koch's postulates. The controls remained symptomless. This is the first report of Selenophoma as the causal agent of browning and necrosis in Lavandula hybrida in Argentina.