ESSENTIAL OILS FROM CLOVE AFFECT GROWTH OF PENICILLIUMSPECIES OBTAINED FROM LEMONS

摘要

Continuous use of fungicides to control citrus postharvest diseases has led to increasing resistant strains of pathogens. Since the appearance of fungicide resistance has become an important factor in limiting the efficacy fungicide treatments, new studies have been needed in order to improve control methods. There is a growing consumer's concern about the possible harmful effects of synthetic fungicides on the human health and the environment. Alternatives to synthetic fungicides for citrus decay control include essential oils. These compounds are known for their natural components and they are searched for potential bio-active plant extracts against fungi. In this study, two isolates of P. digitatum and P. italicum each were collected from lemon fruits affected by green and blue mould, respectively. Isolates were purified in potato dextrose agar (PDA) in order to separate the two species which we are demonstrated that they commonly grow together in nature. In vitro assays, in which isolates weregrown at 26°C on Petri dishes containing PDA for up to 17 days, were carried out by pouring several doses of essential oils from clove {Syzyg-ium aromaticum l.) on PDA to obtain the following concentrations (v/v): 1.6; 8, 40, 200 and 500 muL L~(-1) + tween 80 (0.1 mL L~(-1) ). Mycelial growth curves and growth, conidiation, mass of aerial mycelium and co-nidial size were measured. Penicillium isolates showed a slight degree of variability in their growth kinetics, depending on the isolate. 500 muL~(-1) inhibited the growth of all the isolates, whereas concentrations lower than 40 muL~(-1) slightly increased the growth. 200 muL~(-1) reduced both growth and conidiation in all isolates. Aerial mycelium of P. digitatum was not affected by clove, whereasreduced the mass of mycelium of P. italicum at concentrations higher than 8 u.L L'1. In vivo experiment was carried out inoculating a drop of an extract of conidia with a hypodermal syringe though a puncture reaching the albedo. Fruits inoculated were stored at 23°C and 74% RH for 25 days. Imazalil was used as a fungicide control. The treatment composed by 25% of commercial dose of imazalil plus 200 ul L'1 of clove was the best to reduce decay until 10% of commercial dose of imazalil. In addition, thisexperimental treatment significantly reduced conidiation, therefore could inhibit the decay dispersion during storage. This suggests that treatments based on both imazalil and clove essential oils may have potential effect in controlling both green andblue mould.