The Effectiveness of Botanical Pesticide as Antifungal on Chili (Capsicum annum L) Disease

Chilli (Capsicum annum L) is a horticulture commodity with a large scale of consumption in the world. In Mexico, chili is usually used in many traditional cuisines such as “Oaxacan black mole” and become international recognition as a culinary spice [1]. Unfortunately, the chili disease caused by some of the pathogen species reduces the quality and quantity of chili production significantly [2]. Some of the main chili diseases include anthracnose, geminivirus, leaf spot, and Fusarium wilt. Chili disease can inhibit plant growth and reduce production ranging between 20-80%. Colletotrichum sp. and Phytophthora capsici are the some of the fungal pathogen in chili disease. Colletotrichum sp. is causative agents of anthracnose diseases and caused yield losses of up to 50% [3, 4] and P. capsici caused leaf blight in chili [5].

In the field, farmers still used synthetic pesticides to control chili diseases. Synthetic pesticides are known have a negative effect to environment, human health, and natural enemies [6, 7]. It has encouraged the researcher to developed of alternative non-synthetic pesticide to control chili diseases [8, 9]. One of the alternative methods is developed a botanical pesticide [10, 11].

Botanical pesticide is an important part of the concept of organic and sustainable agriculture because it is environmental friendly and safe for the human health [12]. It is derived from plants which have naturally occurring defensive properties. Many plants have been reported used as a botanical pesticide and showed promising results [13].

Anacardium occidentale, Chromolaena odorata, Cassia alata and Albizia saponaria are reported to inhibit the Phytophthora palmivora on cocoa [14]. Sarkhosh et al. [15] reported that essential oil from mint (Mentha piperita Willd.), savory (Satureja khuzistanica Jamzad.), thyme (Thymus daenensis Celak.), cinnamon (Cinnamomum zeylanicum Blume.) can inhibit mycelial growth of Colletotrichum, Botryosphaeria, Fusarium, and Phytophthora. Other reports show that the essential oils of lemongrass (C. citratus L), citronella (Cymbopogon nardus (L.)), and peppermint (Mentha piperita L.) effectively suppress the growth of Helminthosporium sp. [10]. Orange peel essential oil contains 96.6% limonene and perfectly inhibit Aspergillus flavus growth [16].

There are many plants that can be used as sources of botanical pesticide, included Jatropha curcas, Toona sureni, and Pangium edule and S. aromaticum and C. citratus L. However, to our knowledge, no studies have identified these plants in controlling chili disease. Therefore, research related to this topic is essential, since it will provide environmentally friendly pesticides that positively affect human health.

While in Indonesia itself, chili is used as a spice in various dishes that are consumed daily. In the rainy season in tropical areas such as Indonesia, plant diseases become the biggest obstacle to yield gain because, if not handled properly, the loss of yield quantity can reach 100%. At the same time, chemical control causes health problems and chemical pollution. It drives the enthusiasm to get a chili vegetable fungicide that effectively controls pathogenic chili fungi.

The aim of this research was to evaluate the effectiveness of antifungal extract of Jatropha curcas, Toona sureni, and Pangium edule and S. aromaticum and C. citratus L to againts the causative agent in chili disease so it will be known which one is the most effective as an anti-fungal. The results showed that the inhibition on colony development of Colletotrichum sp. and Phytophthora capsici tested was significant.

The growth of P. capsici was faster than that of Colletotrichum sp. At 6 DSI, control treatment showed P. capsici reached 5.16 cm on colony diameter and 3.74 cm for Colletotrichum sp. Colletotrichum sp. tends to be stronger against the provision of botanical pesticides. P. capsici did not show growth of mycelium until the end of observation, whereas Colletotrichum sp. began to show there was hyphal development in 6 DSI.

The major chemical composition of the essential oil extracted was different depending on botanical pesticide material. The dominant compounds in J. curcas extract was phenol (81.87%), suren contained a lot of 9,12-Octadecadienoic acid (Z, Z) - and Phytol acetate, and Squalene (37.08%) and Farnesol isomer (29.55%) were the dominant compound in P. edule. The major compounds in the two essential oils were very specific, such as eugenol in S. aromaticum and citronellal in lemongrass. The composition of eugenol in S. aromaticum was 70.97%, and citronellal (44.23%) and geraniol (23.84%) in lemongrass.

3.2 Discussion

The present investigation showed that two essential oils tested, had high in vitro antifungal activity against Colletotrichum sp. dan P. capsici. The previous studies showed that these oils have been shown to inhibit several plant pathogenic fungi growth. Sharma et al. [20] reported that S. aromaticum oil exhibited complete inhibition Fusarium oxysporum f. sp. lycopersici growth and spore germination at 125 ppm. Costa et al. [21] evaluating the S. aromaticum essential oil effect on the hyphae of Rizoctonia solani, F. Solni, and F. oxysporum, found different morphological changes and inhibition of hyphal development. S. aromaticum oil also can suppress the growth of bacterial wilt in tomatoes [22]. C. citratus L essential oil impacts on colony growth and spore production of C. coccodes, Botrytis cinerea, Cladosporium herbarum, Rhizopus stolonifer and Aspergillus niger [23]. The application of citronella oil on post-harvest fruits shows promising results [24]. In vitro test show that citronella oil can suppress post-harvest pathogen such as Rhizopus stolonifera, Botrytis cinereal, Colletotrichum coccodes, Aspergillus niger, and Cladosporium herbarum [23].

Only P. edule extract that was effective significantly as antifungal from tree botanical extract tested. Previous study informed that P. edule extract had ability to inhibit the growth of A. flavus [25], C. capsici [19], and C. gloeosporioides [26]. The major chemical composition of were Squalene and Farnesol isomer (Table 3). Squalene reported effected to ergosterol biosynthesis, inhibition of the terminal oxidase, and transport electron [27]. Georgopapadaku and Bertasso [28] reported that effect of squalene were biosynthesis inhibition, membrane integrity, and cell growth inhibition in Candida albicans.

Based on the results of the GCMS analysis of the extracts of the four vegetable pesticides studied, several secondary metabolites were found, the main compounds being phenol, octadecadienoic acid, phytol acetate, farnesol, citronellal, geraniol, eugenol.

Jatropha leaf phenol extract obtained seven peaks, indicating the presence of 7 secondary metabolites, which showed mass spectrum or rest area greater than 3%. The main compounds identified were Phenol (range area 81.87%). The other research reported that the presence of saponins, steroids, tannins, glycosides, alkaloids, and flavonoids was discovered during the phytochemical screening of J. curcas stem bark extracts [29]. J. curcas Linn. leaf and latex extracts, contained appreciable amounts of phenolic and saponin compounds [30].

The content contained in jatropha leaves includes alkaloids, saponins, tannins, phenolics, and flavonoids [31]. The chemical compound used as a producer of biofuels, jatropha is also used in other forms, such as for lubricating oil and raw materials in making soap. High-quality raw materials in the insecticide, fungicide, and molluscide industries [32]. These chemicals are known to be physiologically active and so help J. curcas antibacterial activity. These secondary metabolites have antibacterial action via various methods [29]. These extracts also showed good antioxidant activity towards DPPH and NO radical scavenging activity [30].

Suren plant extract contains 32.15% octadecadienoic and 30.56% phytol acetate; both compounds have the potential as antifungal agents [33]. The kluwek plant contains farnesol which has the potential to be a plant-based fungicide. Citronellal and geniol in citronella extract reached 44.23% and 23.84%, respectively. Citronellal, geraniol, and citronellol are the main ingredients in citronella oil that can be used as antibacterial [34, 35]. The repellency of T. sureni seed extracts against the red flour beetle increased proportionally with the concentration of the extract [36].

Clove oil, according to GCMS, contains 70.97% eugenol, which is used in the perfume industry and can also be used as an antiseptic. The other research reported the main constituents of clove essential oil are phenylpropanoides such as carvacrol, thymol, eugenol and cinnamaldehyde [37]. According to research conducted by Campaniello et al. [38], eugenol is an effective antifungal compound. The presence of eugenol activity that can inhibit the growth of Aspergillus niger, A. terreus, Emericella nidulan expansum, P. glabrum, P. italicum, Fusarium oxysporum, and F. avenaceum with different concentrations.

Farnesol has the capability as an antifungal associated with the inhibition of fungal dimorphism. Fermesol can damage the cell membrane of pathogenic fungal hyphae and can interfere with the process of biofilm formation. Fermesol has widly used on farmacical industry as alternatif antifungal.

The antifungal activity of essential oils related to the presence of bioactive terpenes, phenolic acids, alcohols, hydrocarbons and aldehydes. S. aromaticum essential oil contains eugenol which include on phenolic compound. Eugenol was known to have antimicrobial ability in some pathogenic fungi, yeast and bacteria [39-41].

Mode of actions of eugenol in controlling fungal pathogen were disintegrating mycelia, inhibition of germ tube formation, inhibition of ergosterol synthesis, and disturbance of membrane permeability. The research conducted by de Oliveira Pereira et al. [42] shows that giving eugenol to the fungus growing media caused weight loss of dry mycelium. Pinto et al. [40] evaluated the effect of eugenol on the content of ergosterol. Ergosterol is the major sterol component of the fungal cell membrane. The results showed a threefold decrease in sterols in fungi treated with eugenol compared with controls [10].

The effect of eugenol on the permeability of the outer membrane has been proven by [39] by using violet crystal dye. Crystal violet penetrates the outer membrane easily enters when the membrane is defective, inversely proportional to normal conditions. The experiments were carried out on Salmonella typhi treated with eugenol and compared with control cells. The result showed that eugenol alters membrane permeability and makes the cells hyperpermeable to solutes, which are generally less permeable. The other research reported that S. aromaticum has better antimicrobial efficacy than O. sanctum to against planktonic and biofilm forms of E. faecalis [43].

Citronellal and geraniol are the two highest compounds contained in C. citratus L oil, based on the results of GC-MS analysis. The antifungal activity of C. citratus L is strongly suspected to involve the role of the compound. Previous study showed that two monoterpenoids (citronellol and geraniol) showed outstanding antifungal activity against Cladosporium carrionii, C. cladosporioides, and C. oxysporum [44]. Pereira et al. [45] reported that citronellol and geraniol had an effect on the mycelial dry weight, conidia germination, and conidiogenesis of Trichophyton rubrum. It's also inhibited the essential compound on cell membrane (ergosterol) biosynthesis.

Their antifungal mode of action involves destructing plasma membrane lipid bilayer. Disruption of the membrane enzymes activity, and interrupt the process of solute transport, metabolism regulation, ergosterol synthesis, cell wall formation and morphogenesis [46]. However, the cultivation of red chilies has its own challenges, especially diseases caused by fungi [47]. Therefore, the development of this botanical pesticide is important for red chili production.

The results of this study will be the basis for the development of botanical pesticides in the future. C. citratus L was the plant that gave the best inhibitory effect against the two tested pathogens. After knowing this information, farmers can try using oil or C. citratus L extract as an alternative to using synthetic pesticides.