Effectiveness of Cymbopogon citratu s Oil Encapsulated in Chitosan on Colletotrichum gloeosporioides Isolated from Capsicum annuum


Abstract

One of the principal etiological agents associated with losses in horticultural crops is the fungus Colletotrichum sp. This study aimed to evaluate the in vitro effectiveness of the essential oil (EO) from Cymbopogon citratus in chitosan supports for the control of Colletotrichum gloeosporioides isolated from sweet pepper plants.

Methods: The extraction and phytochemical analysis of the EO of C. citratus were performed along with its encapsulation in chitosan-agar in order to compare it with other techniques and determine its effect on C. gloeosporioides.

Results: The EO from the citral chemotype (58%) encapsulated in the chitosan-agar, with an 83% encapsulation efficiency in mass percentage, resulted in the total inhibition of mycelial growth at a minimum inhibitory concentration of 1370 ppm. This concentration was effective in controlling the disease under greenhouse conditions. The effectivity of the capsules containing EO was superior to that of other controls using EO evaluated in vitro. The capsules demonstrated an effective period of 51 days, with an additional 30 days of effectiveness after a reinfection cycle, thus providing similar results to the control with Trichoderma sp.

Conclusions: Chitosan capsules present a promising strategy in the use of C. citratus EO on C. gloeosporioides, and they are highly effective and stable under in vitro and field conditions.

Keywords: anthracnose; citral; encapsulation; lemongrass; sweet pepper.

Conflict of interest statement

Adriana Patricia Tofi?o-Rivera, Glorismar Castro-Amaris and Fánor Casierra-Posada declare that they have no competing interest.

Figures

Figure 1
Figure 1
Verification of amplification of the internal transcribed spacer region (ITS) region by 1% agarose gel electrophoresis. The bp values shown are approximated. Code 2 corresponds to Colletotrichum gloeosporioides.
Figure 2
Figure 2
Chromatogram of the essential oil from lemongrass. The first peak (A) represents myrcene, the second peak (B) represents neral, and the third peak (C) represents geranial.
Figure 3
Figure 3
Cumulative EO percentage released from optimized capsules in a phosphate buffer (Ph 7.4).
Figure 4
Figure 4
Comparison of the effectiveness of techniques using Cymbopogon citratus EO in the inhibition of mycelial growth of C. gloeosporioides up to 30 days.
Figure 5
Figure 5
Consistency and weight measurement process during days 15, 30, and 45 of the test with a 100%, 50%, and 10% reduction in weight, respectively (A–C). Weight loss ratio of Chitosan-Agar-EO capsules from day 1 to day 45 (D–F).
Figure 6
Figure 6
EO chitosan capsule weight stability.
Figure 7
Figure 7
Day 1 of the test to evaluate the antifungal activity of EO capsules in greenhouse conditions: Topito chili plants infected with 1 × 106 conidia mL?1 with treatments of 20, 30, and 40 capsules of (Chitosan-Agar-EO) from Cymbopogon citratus.
Figure 8
Figure 8
Damage assessment of Topito peppers at different durations. Day 10 (A–F) and 51 (G–L) of evaluation: peppers and leaves with slight signs of infection in treatment with 20 capsules of EO and without signs of infection in treatments with 30 and 40 capsules of EO. Peppers and leaves with serious signs of infection in controls with 20, 30, and 40 capsules of corn oil.
Figure 9
Figure 9
Difference between Topito peppers from infected plants and those treated with capsules (Chitosan-Agar-EO) of Cymbopogon citratus (A) and Chitosan-AGAR-Corn Oil (B).
Figure 10
Figure 10
Diagram of the system used for testing the in vitro volatile effect of the de EO-agar-chitosan capsules.
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