Effectiveness of essential oils in the treatment of Colletotrichum truncatum-infected soybean seeds

Abstract

The aim of the study was to evaluate the antifungal activity of essential oils from "hortelã do campo" (Hyptis marrubioides), "alfazema-do-Brasil" (Aloysia gratissima) and "erva-baleeira" (Cordia verbenacea) and their efficacy in the treatment of soybean seeds infected with Colletotrichum truncatum. In vitro assays were performed to evaluate the effects of the oils on spore germination, mycelial growth, and the production and viability of C. truncatum conidia. Soybean seeds inoculated with C. truncatum were treated with essential oils at concentrations ranging from 0.5 to 2% and grown under greenhouse conditions. Seed health and germination percentages were evaluated according to standard protocols. Seedling emergence, stand establishment and the percentages of dead seedlings were determined, together with the emergence speed index, plantlet height and dry weight of aerial biomass. The oils from H. marrubioides, C. verbenacea and A. gratissima inhibited the germination and production of conidia as well as the growth of C. truncatum. At concentrations ≥ 1%, the effectiveness of the oils against soybean anthracnose was superior to, or at least comparable with, that of the fungicide carbendazim. The viability of conidia and the germination of soybean seeds were not affected by any of the treatments with essential oils. It is concluded that essential oils from H. marrubioides, A. gratissima and C. verbenacea have potential as alternatives to synthetic fungicides in the control of anthracnose in soybean seeds.

Antifungal activities of methanol extracts of some medicinal plants against germination and growth of Colletotrichum destructivum O’Gara in culture

“…However, in this study, the antifungal activity of the test plants against the spore germination and radial growth of C. destructivum were inferior to benomyl and did not confirm the report of Costa da Silva et al (2012; where the extract of Hyptis marrubioides was significantly superior to carbendazim in inhibiting the spore germination and radial growth of C. truncatum and Phakopsora pachyrhizi causing anthracnose disease and rust of soybean respectively. The pesticide activity of botanicals is based on the type of its active chemical principle, and amount of functional groups involved (Enyiukwu and Awurum 2012).…”

Local and systemic control of powdery mildew in eucalyptus using essential oils and decoctions from traditional Brazilian medicinal plants

“…While Silva et al. (,b, ) observed that the preparations derived from these plant species were very effective against Asian soybean rust and in the treatment of soybean seeds infected by Colletotrichum truncatum , no information is available concerning the effects of these products on Oidium and on the induction of resistance to fungal infection.…”

“…The essential oils of these three species of plants have also been shown to be effective in the control of phytopathogens (Silva et al. ,b, ). In the present study, we have investigated the local and systemic effects of the essential oils and decoctions derived from these plant species on the control of O. eucalypti in a highly susceptible hybrid Eucalyptus urophylla × Eucalyptus camaldulensis (‘urocam’).…”

Treatment of soybean seeds to control pathogenic fungi and maintain physiological quality

“…The pathogen can affect the plant at any stage of development and can cause seedling death; necrosis in petioles and ribs; spots on leaves, stems, and pods; total fall of pods; and total deterioration of seeds in late harvest. Losses can reach up to 100% under conditions of temperature and humidity favorable to fungal development (Silva et al, 2012). Furthermore, when present in the seeds, the pathogen can reduce germination by affecting their physiological quality, or later damage seedlings (Machado, 2012).…”