Abstract

FOGLIATA, Gabriela M. et al. Identification of Fusarium oxysporum as the causal agent of a peduncle rot in Tucumán, Argentina and in vitro efficacy of fungicides for its control. Rev. ind. agric. Tucumán [online]. 2018, vol.95, n.2, pp.15-24. ISSN 1851-3018.

In 2007, a peduncle rot with presence of mycelium was detected in lemon fruits stored in commercial packinghouses in Tucumán. This disease, known as "Fusarium rot", can be caused by different species of the genus Fusarium. Although it is considered a disease of low importance, due to its occasional occurrence, significant losses in orange and grapefruit fruits have been reported in other countries. The current study was conducted to identify the causal agent of lemon peduncle rot in Tucumán, evaluate its damage in fruit and estimate the in vitro efficacy against its causal agent, of postharvest fungicides currently used for control of other fruit rots. During the years 2007 to 2011, 22 strains were collected, which were all identified as Fusarium oxysporum by morphological and cultural characterization, PCR and sequencing. Pathogenicity tests were performed on fruit by artificial inoculation and the fungus re-isolated on PDA. In order to evaluate the incidence and type of damage, lemon fruits, untreated or treated with sodium hypochlorite, alone or with ethephon were stored under predisposing conditions, resulting in an incidence of 14.0%, 22.5% and 41.0%, respectively. Peduncle rot did not advance towards the peel or internal tissues of the fruit. The highest in vitro efficacy, inhibition of mycelial growth of the pathogen in PDA, was obtained with carbendazim (EC95 1.5 mg/L) and propiconazole (EC95 7.2 mg/L). Azoxystrobin+fludioxonil, imazalil, thiabendazole and imazalil+pyrimethanil, were less effective (EC95 of 46.6 mg/L, 56.3 mg/L, 84.3 mg/L and 93.9 mg/L, respectively). Fusarium oxysporum was confirmed as the causal agent of peduncle rot in lemon in Tucumán, with development of white mycelium and with the rot only restricted to the peduncle. Among the most effective fungicides in vitro, carbendazim has restrictions on its use, both for fresh fruit and for industry, so it is of interest to evaluate propiconazole in in vivo tests.

Keywords : imazalil; carbendazim; propiconazole; EC95.

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