Extrato de alho no controle in vitro e in vivo da antracnose da videira

Abstract

The aim of this study was to evaluate the in vitro and in vivo efficacy of the crude extract of garlic in controlling anthracnose of grapevine (Elsinoe ampelina). In the first experiment in vitro, 0, 5, 10, 15, 20, 25 or 30 mL L-1 crude extract of garlic were added to potato-dextrose-agar medium (PDA) before autoclaving for sterilization and to melting media. After 3, 5, 7 and 9 days of incubation at 24 ± 2°C and photoperiod of 16 hours, the mycelial growth of E. ampelina was measured. In the second experiment in vitro, we repeated the methodology of adding the extract to the melting medium plus 2.5 mL-1 of vegetable oil and an absolute control with PDA only. After two and four hours of incubation at 24°C and constant light, germination of E. ampelina was assessed. The experimental design for in vitro experiments was completely randomized with four replicates and the experimental plot consisted of a Petri dish. In the field experiment, after pruning of the grapevine cv. Isabel, the levels of crude extract of garlic plus oil were weekly sprayed on the leaves of the plant, except on the absolute control (no treatment). From the first symptoms of anthracnose of grapevine, the severity that was expressed as area under the disease progress curve (AUDPC) was evaluated. The design was in randomized blocks with five replicates. The crude extract of garlic reduced the mycelial growth of the pathogen, especially when added to the culture medium prior to sterilization, when it expressed its maximal antifungal potential. When the vegetable oil was added to the extract levels, there was complete inhibition at the levels 25 or 30 mL L-1. This additive effect of these compounds was also noted for the germination test of E. ampelina. Under field conditions, the crude extract of garlic reduced the AUDPC by 83.59% at 25 mL L-1.