Abstract
Colletotrichum gloeosporioides and Pseudopestalotiopsis camelliae-sinensis are the two most important tea plant (Camellia sinensis L.) pathogenic fungi. Interest in natural plant extracts as alternatives to synthetic chemical fungicides to control plant pathogens is growing. In this study, the volatile fraction of Baeckea frutescens L. was extracted by supercritical fluid extraction (SFE-CO2), and its chemical composition was analyzed, and investigated for its antifungal activity against C. gloeosporioides and P. camelliae. The major constituents of the volatile fraction were β-caryophyllene (28.05%), α-caryophyllene (24.02%), δ-cadinene (6.29%) and eucalyptol (5.46%) in B. frutescens SFE-CO2 extracts. The terpineol, linalool, terpinen-4-ol and eucalyptol showed strong contact antifungal activity against P. camelliae and C. gloeosporioides with median inhibitory concentration (MIC50) in the range of 0.69 μL/mL to 2.79 μL/mL and 0.62 μL/mL to 2.18 μL/mL, respectively. Additionally, the volatile fraction had high fumigation antifungal activity against P. camelliae and C. gloeosporioides with an inhibition rate between 20.87% and 92.91%. Terpineol presented the highest antifungal activity in the contact and fumigation toxicity assays. Terpineol, linalool, terpinen-4-ol and eucalyptol were associated with the most active chemical compounds in the volatile fraction against the fungi. The results suggest that B. frutescens SFE-CO2 extracts are potential ingredients to develop a natural fungicide for control of tea plant pathogens.
Highlights
As an alternative to using chemical fungicides, plant extracts have attracted the attention of chemical companies as they may be used as botanical fungicides
The tea plant suffers from biotic stresses of some pathogenic fungi, which is a serious concern for the tea industry as this condition impacts on reduced tea yields, decreased quality and damaged human health [9,10]
Materials of the extract obtained by Supercritical fluid extraction (SFE)-CO2 was 2.2% (w/w relative to dry material weight)
Summary
As an alternative to using chemical fungicides, plant extracts have attracted the attention of chemical companies as they may be used as botanical fungicides. Baeckea frutescens L. is an important medicinal plant belonging to the Myrtaceae family [1] and is found in Peninsular Malaysia and Sumatra and distributed along coastal areas of southeastern China and Australia [2]. The leaves of B. frutescens are rich in various volatile constituents such as terpenoids, sesquiterpenes and phenylpropanoids, which are secondary metabolites associated with numerous bioactivities [1,5,6]. The tea plant (Camellia sinensis L.) is a crucial commercial crop in world [7]. Made from fresh leaves of C. sinensis, is a prominent beverage worldwide and is the second most consumed nonalcoholic beverage after water [8]. Pseudopestalotiopsis camelliae-sinensis was shown to cause grey blight disease on tea plants in China [13]. Some research has showed that planting disease-resistant varieties of
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