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Original Article • Braz. J. Biol. 85 • 2025 • https://doi.org/10.1590/1519-6984.294377 linkcopy

Open-access Preventive control of post-harvest diseases in citrus (orange, mexican and lemon) using noni essential oil and Saccharomyces Cerevisiae

Controle preventivo de doenças pós-colheita em citros (laranja, mexerica e limão) utilizando óleo essencial de noni e Saccharomyces Cerevisiae

AuthorshipSCIMAGO INSTITUTIONS RANKINGS

Abstract

Citrus fruits (Citrus) are of great importance in the fruit production chain in Brazil. With a significant contribution to the country's economy. However, post-harvest diseases negatively affect the quality and quantity of fruits that would be marketed. Thus, the main objective of the work was to evaluate the effect of noni essential oil (Morinda citrifolia) and commercial Saccharomyces cerevisiae (Fleischmann) in the control of post-harvest diseases in citrus. The pathogenic isolates were obtained from diseased citrus fruits collected at the local market in the city of Gurupi-TO. Noni essential oil was extracted using the hydrodistillation method. In vitro tests with noni essential oil were performed at concentrations of 1.25; 2.5; 5; 10 and 30 mg mL-1 and a solution based on sterilized distilled water was prepared for the yeast at concentrations of 1%, 2%, 3%, 4% and 5% evaluated for 10 days with intervals of 48 hours maintained at 25 ± 1°C. The phytotoxicity test was evaluated at the same concentrations. For in vivo tests, the same concentrations as in vitro tests were used. The isolated pathogens that attack the fruits in the post-harvest are Penicillium sp., Guignardia sp. and Aspergillus sp. Etiology confirmed by pathogenicity test. By means of gas chromatography (GC/MS) the major compound identified in noni essential oil was octanoic acid (92.02%). The best in vitro fungitastic activity of noni essential oil was achieved at a concentration of 30 mg mL-1, inhibiting the mycelial growth of the pathogens Penicillium sp. and Guignardia sp. at 100%. S. cerevisiae showed better fungitastic activity from the concentration of 3%, 4% and 5% for the pathogen Penicillium sp. with inhibition of 76%, 87% and 88% and Aspergillus sp. with 100% inhibition at both concentrations (4% and 5%). The noni essential oil did not show phytotoxicity in the fruits. The two in vivo treatments showed protective action, especially the yeast S. cerevisiae. Based on the results we can conclude that the essential oil of noni and the yeast S. cerevisiae present themselves as a good alternative in the biological control of pathogens characteristic of post-harvest in citrus fruits.

Keywords:
Morinda citrifolia; biological control; yeast; citrus fruits

Resumo

As frutas cítricas (Citrus) são de grande importância na cadeia produtiva de frutas no Brasil. Com contribuição significativa para a economia do país. Contudo, doenças pós-colheita afetam negativamente a qualidade e quantidade dos frutos que seriam comercializados. Desta forma, o objetivo principal do trabalho foi avaliar o efeito do óleo essencial de noni (Morinda citrifolia) e Saccharomyces cerevisiae comercial (Fleischmann) no controle de doenças pós-colheita em citros. Os isolados patogênicos foram obtidos a partir de frutas cítricas doente coletadas no mercado local da cidade de Gurupi-TO. O óleo essencial de noni foi extraído utilizando o método de hidrodestilação. Os testes in vitro com óleo essencial de noni foi realizado nas concentrações de 1,25; 2,5; 5; 10 e 30 mg mL-1 e para a levedura foi preparada uma solução a base de água destilada esterilizada nas concentrações de 1%, 2%, 3%, 4% e 5% avaliados por 10 dias com intervalos de 48h mantidos a 25 ± 1 ºC. O teste de fitotoxidez foi avaliado nas mesmas concentrações. Para os testes in vivo foram utilizadas as mesmas concentrações dos testes in vitro. Os patógenos isolados que atacam os frutos na pós-colheita são Penicillium sp., Guignardia sp. e Aspergillus sp. Etiologia confirmada por meio do teste de patogenicidade. Por meio de Cromatografia gasosa (CG/MS) o composto majoritário identificado no óleo essencial de noni foi o ácido octanóico (92,02%). A melhor atividade fungitástica in vitro do óleo essencial de noni foi alcançada na concentração de 30 mg mL-1 inibindo o crescimento micelial dos patógenos Penicillium sp. e Guignardia sp. em 100%. A S. cerevisiae apresentou melhor atividade fungitástica a partir da concentração de 3%, 4% e 5% para o patógeno Penicillium sp. com inibição de 76%, 87% e 88% e Aspergillus sp. com inibição de 100% nas duas concentrações (4% e 5%). O óleo essencial de noni não apresentou fitotoxidez nos frutos. Os dois tratamentos in vivo apresentaram ação protetiva, sendo destaque a levedura S. cerevisiae. Com base nos resultados podemos concluir que o óleo essencial de noni e a levedura S. cerevisiae se apresentam como uma boa alternativa no controle biológico de patógenos característicos da pós-colheita em frutas cítricas.

Palavras-chave:
Morinda citrifolia; controle biológico; levedura; frutos cítricos

1. Introduction

Brazil has cultivated agricultural crops of great economic importance for the country, including the production of orange, lime orange, lemon and tangerine. According to Conab, orange production is expected to increase from 15.8 million tons in the 2018/19 harvest to 16.8 million tons in the coming years (CONAB, 2020). The production of citrus fruits recorded annually in the world exceeds 88 million tons and 50% of this production is destined for juice production. Brazil is considered one of the largest exporters of processed citrus fruits. Furthermore, the country is considered one of the largest orange producers in the world (39%). Followed by China with 68.2% of global tangerine production, Mexico, Argentina and the European Union the world's largest producers of lemon and lime (Silva, 2019).

However, pathogenic fungi are the main agents causing the decrease in productivity of citrus crops in Brazil and around the world. Among the possible diseases that can affect citrus post-harvest are green and blue molds caused by P. digitatum and P. italicum respectively, and sour rot caused mainly by G. citri-aurantii. These are the diseases considered most important, in terms of the economy, as in addition to affecting the quality, it also affects the quantity of citrus fruits, devaluing them for fresh trade (Moura et al., 2019). Therefore, the use of natural products as an alternative to control fungal diseases is a promising choice. Because, in addition to reducing the use of pesticides, they contribute to a sustainable environment, and economically viable, since products of biological origin are considered low cost, serving both small and large producers (Costa, 2017).

Essential oils originate from the secondary metabolism of plants, and have in their composition, volatile aromatic compounds such as terpenes and their derivatives, these being the main responsible for its antimicrobial activity. Sarto and Zanusso Junior (2014) state that noni essential oil (Morinda citrifolia) is a sustainable and low-cost alternative, being economically viable. The biotechnological importance of the research consisted in the search for new alternative and environmentally sustainable measures, low cost and reducing the use of chemical products, through the use of noni essential oil and S. cerevisiae.

2. Material and Methods

The phytopathogens were isolated from diseased fruits obtained from supermarkets located in the city of Gurupi-TO. The parts of the fruits with symptoms of the disease were cut into 8 mm fragments and washed in running water. Then, they were superficially disinfected by consecutive portions in 70% alcohol for 30 min, 1% hypochlorite solution for 40 min and three times in sterile distilled water. Afterwards, with the aid of sterile harvesting, the fragments were transferred to Petri dishes containing 20 mL of PDA culture medium prepared with the addition of the antibiotic amoxicillin (500 mg) and then sealed with plastic film. After 10 days of incubation under photoperiod (12 hours light and 12 hours dark) and temperature at 25°C in BOD, colony coloration and presence or absence of chlamydospores were evidenced. After supervision, the Petri dishes containing fungal colonies were subdivided using 5 mm diameter discs containing fungal mycelium onto new plates with the same culture medium, obtaining a pure colony (Valadares, 2009). The pathogenicity test (Koch's Postulate) was carried out according to the methodology of Moura (2019, adapted).

The extraction of the essential oil was carried out by the hydrodistillation method, using the modified Clevenger apparatus. The extraction process was carried out over a period of 2 hours, keeping the solution boiling. After 2 hours, the essential oil was collected with the aid of a Pasteur pipette and stored at 10°C in an amber glass bottle wrapped with aluminum foil, protected from light until its use in in vitro and in vivo tests (Seixas et al., 2011, adapted). The determination of the composition of noni essential oil was carried out using Gas Chromatography Coupled with Mass Spectrometry (GC/MS) (Model GC-2010) [GCMS-QP2020 Program].

For bioassays of the fungistatic activity of noni essential oil, concentrations of 1.25, 2.5, 5, 10, 30 mg/mL-1 of noni essential oil prepared with Tween 80 were prepared. As a positive control, a bioassay was set up with sterile distilled water. and a bioassay with 2% Methyl Thiophanate fungicide as a negative control. After preparation, 200 µL of each concentration was added to the petri dish containing PDA culture medium, the concentrations were distributed over the medium using a Drigalski loop. Then, 5 mm diameter mycelium-agar discs of the fungi were inoculated in the center of the plate with the respective treatments. Subsequently, the plates were sealed with plastic film and incubated in a BOD chamber (25 ± 1 ºC). Radial growth was measured for 10 days at 48-hour intervals (Barros et al., 2019, adapted). Statistical analysis was performed using ANOVA using the Sigma Plot 11.0 and Excell 2010 programs.

For the fungistatic activity of the commercial yeast S. cerevisiae (Fleischmann), bioassays were prepared in which the yeast was diluted in sterile distilled water at concentrations of 1%, 2%, 3%, 4% and 5%, then added to medium of PDA culture (Potato-Dextrose-Agar) 200 µL of each S. cerevisiae yeast suspension. As a positive control, a bioassay was set up with sterile distilled water and a bioassay with 2% Methyl Thiophanate fungicide as a negative control. The treatments were prepared in a 15 x 1 x 5 factorial scheme following the combination of a phytopathogenic fungus and five concentrations of the yeast S. cerevisiae. The entire bioassay was set up according to the methodology proposed and used by Barros et al. (2019, adapted).

The solution preparation methodology used in this stage was the same as that used in in vitro tests, only the volumes to be applied varied, as well as the positive and negative control. Conidial solutions were prepared at a concentration of 105 conidia mL-1. Different concentrations of noni essential oil and S. cerevisiae solution were applied to the fruits with the aid of a flexible rod (cotton swabs). Approximately two hours after applying the solutions (200 µL), the pathogen was placed (100 µL) on the fruits using a pipette and then the fruits were kept in a humid and dark chamber for 48 hours. Subsequently, the fruits were placed in a natural environment with a temperature ranging from 25°C ±2ºC for the development of the disease. Four days after inoculation, five assessments of the severity of the disease were carried out with an interval of two days using the rating scale adopted by Costa (2017). From the grade values ​​obtained in the evaluations, the area under the disease progression curve (AACPD) was calculated according to (Ferreira et al., 2018).

3. Results

The microorganisms isolated from citrus fruits were: the fungus of the genus Penicillium sp. identified in the orange fruit (Figure 1A and figure 1B), Guignardia sp. isolated from tangerine fruit (Figure 1C and figure 1D) and Aspergillus sp. isolated from the lemon fruit (Figure 1E and figure 1F). They are pathogenic agents characteristic of post-harvest diseases in citrus crops.

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Figure 1
Morphological structure of the fungus Penicillium sp. (A) and orange infected by the pathogen (B); Morphological structure of the fungus Guignardia sp. (C) and infected by the pathogen (D); Morphological structure of the fungus Aspergillus sp. (E) and Lemon infected by the pathogen (F).

Based on the morphological structures identified and expressed in Figure 1 and the symptoms of the disease in the fruit (Figure 1B), it is possible to identify the isolated fungus. Figure 1A shows the morphology that characterizes the species of the fungal group Penicillium sp., which causes green mold in citrus fruits. This species of fungus produces spores that form olive green colonies with a white border. It is responsible for causing green mold in orange fruits, a disease that directly affects the quality of the fruit, preventing its sale. The morphological structure of the pathogen's conidiophores is similar to the shape of a broom with branches (La Spada et al., 2021).

In relation to the morphological structure presented in Figure 1C and the symptoms in the fruit (Figure 1D) and based on the literature examined, the structure identified above characterizes the pathogenic fungus Guignardia sp., the main causal agent of black spot disease in citrus, specifically in tangerine. The fungus has circular structures called cylindrical-shaped asci, dark in color and connected to translucent septa. The disease has a great influence on the appearance of the fruit, as it presents irreversible lesions on the surface of the fruit, leaving it with an undesirable appearance for sale (Tran et al., 2018).

In Figure 1E, the pathogen has a morphology characteristic of the pathogenic fungus Aspergillus sp. Aspergillus sp. is responsible for large losses in different foods with a high level of contamination due to excessive sporulation of the pathogen, it causes a direct impact on fruit productivity as it is a pre- and post-harvest disease. In its morphological structure, the fungus has a stipe linked to a globose vesicle, characterized by metulae and phialides connected to conidia in the surface area. The fruit contaminated by the pathogen Aspergillus sp. becomes a disposable fruit, due to loss of quality.

The hydrodistillation method adopted to extract noni essential oil was efficient with a yield of approximately 1.8 mL per extraction. According to the result obtained in the chromatographic analysis (Table 1), the majority constituent identified in the chemical composition of noni essential oil was octanoic acid (92.02%).

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Table 1
Chemical constituents identified in the composition of noni essential oil (Morinda citrifolia) extracted from the fruits.

The fungistatic activity of noni essential oil against the three pathogenic isolates showed that the essential oil showed effective inhibitory activity at the highest concentration of 30 mg mL-1 (Figures 2, 3 and 4). The following graphs allow you to observe the percentage of pathogen growth in relation to the treatment received.

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Figure 2
Fungistatic activity of noni essential oil (Morinda citrifolia) against the pathogenic fungus Penicillium sp.
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Figure 3
Fungistatic activity of noni essential oil (Morinda citrifolia) against the pathogenic fungus Guignardia sp.
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Figure 4
Fungistatic activity of noni essential oil (Morinda citrifolia) against the pathogenic fungus Aspergillus sp.

The fungus Penicillium sp. (Figure 2) showed zero growth percentage at the highest concentration of noni oil (30 mg mL-1), providing 100% inhibition of the pathogen at this concentration. Not statistically different from the negative control Methyl thiophanate (CN) (2%). The other oil concentrations did not show significant results, with a growth rate above 50% being statistically equal or similar to the positive control (CP). The result achieved proves that noni oil in low concentrations does not present fungitoxic action considered effective in inhibiting the pathogen Penicillium sp. Next, figure 3 highlights the results of noni oil in controlling the growth of the pathogen Guignardia sp.

The fungus Guignardia sp. subjected to the fungistatic action of noni essential oil, it showed zero growth at a concentration of 30 mg mL-1 with 100% inhibition of the fungus. While the negative control exhibited growth of 4% with significant inhibition of 96%, the result being statistically similar to the higher concentration of the oil. Concentrations below 30 mg mL-1 did not show significant efficacy in inhibiting the mycelial growth of the pathogen. Note that, on the third day of evaluation, the fungus Guignardia sp. showed 100% growth throughout the plate, only at concentrations of 1,25; 2,5; 5 and 10 mg mL-1. These concentrations did not show inhibitory potential for this pathogen, being statistically analogous to the positive control (CP).

Based on the results obtained for the fungus Guignardia sp. its non-inhibition can be explained by the fact that the oil does not present phytotoxic action against this pathogen at concentrations lower than 30 mg mL-1. Therefore, for the pathogen to have its germination process interrupted, it is ideal to test concentrations above 30 mg mL-1. The literature does not report the use of noni oil to control the fungus Guignardia sp. which makes the current work a novelty in relation to the use of treatment against the pathogen.

Figure 4 shows the fungistatic action of different concentrations of noni oil in controlling the fungus Aspergillus sp.

The fungistatic action of noni oil against the growth of the fungus Aspergillus sp. presented results with a low level of significance, showing a relatively low percentage of inhibition. At the highest concentration (30 mg mL-1) of the treatment, there was 31% inhibition with mycelial growth of 69%, similar to the negative control (CN), which showed 72% growth and 28% inhibition, these being considered statistically unsatisfactory results.

The following results demonstrate the efficacy of the fungistatic action of the Saccharomyces cerevisiae yeast solution as a biocontrol agent for the phytopathogens represented in the following graphs (Figures 5, 6 and 7).

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Figura 5
Atividade fungistática da Saccharomyces cerevisiae frente ao fungo patogênico Penicillium sp.
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Figure 6
Fungistatic activity of Saccharomyces cerevisiae against the pathogenic fungus Guignardia sp.
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Figure 7
Fungistatic activity of Saccharomyces cerevisiae against the pathogenic fungus Aspergillus sp.

The yeast exhibited fungistatic activity at all concentrations tested for the fungus Penicillium sp. The best fungistatic effects of the yeast Saccharomyces cerevisiae were noted at a concentration of 3%. At this concentration, the pathogen grew only 24%, resulting in an inhibition of 76%. At a concentration of 4%, the pathogen showed growth of 13%, exhibiting an inhibition of 87% of Penicillium sp., similar to the concentration of 5%, in which the fungus grew only 12%, presenting an inhibition of 88%. Therefore, fungistatic potential was noted for all concentrations of the S. cerevisiae solution. These results were statistically significant.

However, the percentage of inhibition of the yeast S. cerevisiae was similar to the inhibition induced by the negative control (NC), which provided 10% growth despite some species of fungi already showing resistance to this fungicide. It is worth mentioning that, in the positive control plate (PC), the fungus showed 70% growth. This result scientifically proves the effectiveness of the treatment (S. cerevisiae solution) as a possible alternative in the control of diseases caused in citrus by the pathogen Penicillium sp.

For the fungus Guignardia sp. the Saccharomyces cerevisiae yeast solution was not effective in inhibiting the mycelial growth of the fungus, the pathogen was resistant to all concentrations tested. It was found that within four days the pathogen had already taken the entire plate, which resulted in zero percent inhibition, thus making it unfeasible to use Saccharomyces cerevisiae as a source of treatment for this pathogen. However, the negative control (CN) inhibited the growth of the fungus Guignardia sp. by 85%. proving that this strain did not show resistance to the fungicide.

However, Figure 7, different from the previous figure, shows the results of the fungistatic action of the S. cerevisiae solution in the in vitro control of the pathogen Aspergillus sp.

The S. cerevisiae yeast solution was effective in inhibiting the fungus Aspergillus sp. presenting satisfactory statistical results in all concentrations tested. The treatment was an excellent biological agent in inactivating fungal growth. A Concentrations of 5% and 4% showed better fungistatic activity, inhibiting 100% the growth of the fungus Aspergillus sp. The 3% concentration showed 77% inhibition resulting in mycelial growth of only 23%. The other concentrations (1% and 2%) of the treatment showed growth of 42% and 34% with significant inhibition of 58% and 66% respectively, statistically a result that conferred fungistatic action on the studied pathogen.

For the fungus species Aspergillus sp. the applied treatment presented itself as an excellent alternative, as it exhibited better inhibition efficacy than the negative control (CN). The fungicide did not show significant effectiveness in controlling the pathogen, as it had a mycelial growth of 96% with only 4% inhibition of the fungus Aspergillus sp.

Figure 8 below is the result of the test evaluating the protective effect of essential oil on fresh fruits. When evaluating the graphs, observe the Area Below Disease Progression (AACPD) in orange fruits (Graph 8A), tangerine fruits (Graph 8B) and lemon fruits (Graph 8C). Preventive treatment with noni oil proved to be a good biological alternative in the protective action against diseases caused in citrus fruits by pathogenic fungi such as Penicillium sp. (8A), Guignardia sp. (8B) and Aspergillus sp. (8C).

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Figure 8
Area Below the Disease Progress Curve (AACPD) in citrus. Preventive treatment with noni oil on orange fruit (Penicillium sp.) (A); tangerine (Guignardia sp.) (B) and Lemon (Aspergillus sp.) (C).

In graph 8A, all concentrations of the oil showed protective action in controlling the green mold disease in orange fruits, as the development of symptoms remained below the disease progress curve (AACPD). These concentrations were statistically better than the commercial fungicide Methyl Thiophanate (CN). It is also noted that the best protective effect was found at a concentration of 30 mg/mL-1. In graph 8B, contrary to the result obtained in in vitro tests, the in vivo oil demonstrated an excellent potential for protective action against tangerine fruits in the control of black macha disease, the effect was observed from a concentration of 2,5; 10 and 30 mg/mL-1. The lowest concentration (1,25 mg/mL-1) presented a similar result to the commercial fungicide Thiophanate methyl (CN) and the positive control (CP) without statistically differing from each other in relation to the development of the disease.

However, for the fungus Aspergillus sp. (8C) the best fungistatic action with protective effect presented by noni oil was presented in a higher concentration (30 mg/mL-1) followed by a concentration of 10 mg/mL-1, these being more effective than the commercial fungicide Thiophanate methyl (CN). The remaining observations do not show statistical difference from the positive control. Observe the AACPD in the following graphs and its representativeness in terms of disease prevention and control in orange (A), tangerine (B) and lemon (C) fruits.

The current result proved that noni oil is a good biological agent in the protective action of citrus fruits, and provided significant results in the protection of fruits that are highly consumed in the country.

Figure 9 highlights the preventive effect of the Saccharomyces cerevisiae solution in protecting fruits in vivo. It is possible to evaluate the graphs based on the analysis of the Area Below Disease Progression (AACPD) presented by the evaluated fruits, orange (Graph 9A), tangerine (Graph 9B) and lemon (Graph 9C).

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Figure 9
Area Below the Disease Progress Curve (AACPD) in citrus. Preventive treatment solution for S. cerevisiae in Orange (Penicillium sp.) (A); tangerine (Guignardia sp.) (B) and Lemon (Aspergillus sp.).

The yeast S. cerevisiae provided excellent protective activity to the treated fruits. All concentrations tested (1%, 2%, 3%, 4% and 5%) demonstrated preventive potential in controlling diseases that attack orange (9A), tangerine (9B) and lemon (9C) fruits post-harvest. The treatment protected the fruits by 100% against the action of pathogenic fungi, which was better than the commercial fungicide. In view of the above, only the AACPD referring to the negative control (CN) and the positive control (CP) can be seen in the graph. Therefore, observe the results achieved with the S. cerevisiae based treatment in Figure 9A, B and C. And the AACPD for all concentrations and treatments evaluated.

The results obtained in the current work on the preventive action of noni essential oil and S. cerevisiae are of great relevance and contribution to scientific research and agriculture in the country. Although there are already studies related to the use of noni essential oil, these are considered few, as it is a compound that has a lot to be investigated. Since, from vegetables and their molecules, a low-cost product can be generated, environmentally safe and meeting the needs of small and large producers.

S. cerevisiae is a model yeast, as there is a huge variety of works correlating the application of yeast for different purposes, this characteristic increasingly enriches the idea of ​​researching and carrying out more and more studies with this variety of microorganism.

4. Discussion

The morphological identification obtained for the pathogenic fungus Penicillium sp. is in accordance with that described by Costa et al. (2019). According to the author, the infection initially appears on the skin of the fruit in the form of a spot considered watery, which, under appropriate growth conditions, allows the development of white mycelia, followed by conidia that have an olive green color, thus characterizing the green mold, a disease that directly influences the quality of orange fruits.

Ghooshkhaneh et al. (2018) report that, if the environment has a temperature and humidity suitable for the fungus, it causes damage to the skin of the fruit, causing a stain with a watery appearance, and subsequently forming white mycelia. They also point out that, after the lesion reaches a diameter of 2.5 to 5 cm, the production of olive green spores begins, a characteristic that defines the pathogen.

Silva-Pinhati et al. (2017) report that it is characteristic of the fungus Guignardia sp. the cause of freckled spots on citrus fruits. As described, the pathogen causes damage to the skin of the fruit, leaving it with a necrotic appearance and the presence of pycnidia in the center of these lesions. In a study, the authors state that the spots do not affect the internal part of the fruit, however, they have a direct influence on the appearance of the fruit, which results in the loss of commercial value.

Wickert et al. (2012) describe that citrus fruits contaminated by the fungus Guignardia sp. After the infection process, they have freckled spots with a hard appearance. In their work, the authors describe that the propagation of the fungus occurs through structures known as sexually formed ascospores, or asexual pycnidia.

Silva (2009) confirms in his work that the genus Aspergillus encompasses a number of 132 species divided into 18 groups. The differentiation of fungi in this genus is identified according to their morphological characteristics. Among the species, there is a variation in the color (brown, black, gray, green and yellow) of the pathogen, which is an excellent attribute to be evaluated, thus facilitating the identification of the microorganism.

Dalcin et al. (2017) in chemical analysis of noni oil, also reported octanoic acid as the majority compound with a content of 82.24%. Similar results were obtained by Costa (2017), in his research the author found the same amount of octanoic acid (82.24%).

The inhibition of the pathogen induced at the highest concentration of the treatment may be related to the volatile organic compounds identified in noni oil. These are compounds that have a phytotoxic action for the pathogen in which they can act on the oxidation of lipids that make up the plasma membrane, thus inhibiting the germination of conidia and thus preventing the growth of the pathogen (Russiano et al., 2019).

Costa (2017) proved through his work the effectiveness of noni essential oil in controlling Colletotrichum gloeosporioides, the agent that causes anthracnose in post-harvest papaya. The author found that the essential oil was an excellent inhibitor of the mycelial growth of the pathogen from a concentration of 3000 ppm, thus proving its fungitoxic potential against post-harvest pathogens. There are not many reports in the literature correlating the application of noni oil to control pathogens that act post-harvest on fruits. However, different studies such as that of, Barros et al. (2021) and Dalcin et al. (2017) proved the effectiveness of noni oil on pathogens that cause disease in mango trees, soybean crops and melon crops.

Russiano et al. (2019) studied the action of citronella essential oil in controlling the pathogen Penicillium sp. cause of blue mold disease in post-harvest apple fruits. The authors confirmed in their work that citronella essential oil inhibited the mycelial growth of the pathogen by 100% in the two doses tested (5 μL and 10 μL). The result demonstrates that essential oils are compounds that have potential, as well as being a promising source and classifying as an alternative control option for protecting fruits post-harvest.

However, different essential oils were tested by Mattos (2010) to control the fungus Guignardia citricarpa. The author evaluated the essential oil of mint, citronella, rosemary, eucalyptus, and ginger, in concentrations of 10,000 and 100,000 mL.L-1. However, none of the oils showed antifungal properties against the fungus Guignardia citricarpa. Thus, the result of the current work on the control of the fungus Guignardia sp. is seen as a promising result in controlling the pathogen in the highest concentration of noni oil.

However Nunes et al. (2021) tested the effectiveness of thyme essential oil in controlling Aspergillus niger, Penicillium expansum and Sclerotinia sclerotiorum and it showed 100% inhibition at concentrations of 0.01%; 0.02% and 0.05%. The authors report that they are pathogens that cause diseases after harvesting grains, fruits such as apples and oranges, and vegetables such as carrots and lettuce.

According to the results obtained by ANOVA, the highest concentration indicates that noni oil has potential in controlling the disease green mold and black spot in citrus. Some studies describe that the mechanism of action of essential oils is directly related to the leakage of the cellular content that makes up the fungal cell wall. This is because the constituents of the essential oil act in the oxidation process of the lipids that make up the cell membrane (Russiano et al., 2019).

The research results corroborate the results obtained by Cunha et al. (2020), the authors observed the fungitastic activity of the yeast Candida stellimalicola and Saccharomyces cerevisiae in controlling the pathogen Penicillium italicum, the causal agent of blue mold in post-harvest orange fruits. And they found inhibition above 90% through the yeast C. stellimalicola and 86% inhibition of mycelial growth of the pathogen mediated by the action of S. cerevisiae. This denotes promise in the use of yeast as an alternative source to the use of chemical products.

The literature does not report the use of the yeast S. cerevisiae to control Guignardia sp. However, Toffano et al. (2017) evaluated the effect of volatile organic compounds (VOCs) produced by S. cerevisiae on the control of Guignardia citricarpa and reported that, after 12 days, volatile organic compounds (VOCs) reduced mycelial growth and germination of the pathogen. Such action was mediated by alcohols 3-methyl-1-butanol and 2-methyl-1-butanol. According to the authors, alcohols have the characteristic of damaging the plasma membrane by affecting the structure and stability of the lipid bilayer, directly impacting the permeability of the cellular environment.

Therefore, in the study by Abdel-Kareem et al. (2019) live S. cerevisiae cells were tested to control aflatoxin-producing Aspergillus flavus in coffee beans. According to the author, the maximum inhibition of mycelial growth was 85%, a result considered statistically significant. Therefore, based on the results of the current study carried out, it can be stated that the yeast S. cerevisiae presents itself as an excellent alternative in the biological control of the pathogens evaluated above.

However, Costa (2017) evaluated the protective effect of essential oil in papaya fruits. The author tested noni oil combined with other compounds such as sunflower oil and lippia, and states that the compounds in noni oil combined with others, promoted an inhibitory action on the pathogen Colletrotrichum gloeosporioides, reducing AACPD.

Studies of the severity of the disease in fruits or any other cultivar are of fundamental importance, as they allow viewing and identifying the best treatment to help control and prevent a given disease. Thus enabling, through AACPD (Area below disease progress), a more direct conclusion about the effective protection of the studied bioproduct.

Based on the current results, it can be stated that noni oil presents itself as a good alternative and with great potential for protective action against diseases that occur post-harvest in citrus. It is important to highlight that the ideal is to test this organic compound on fruits during pre-harvest, as this can provide even more significant protection.

It is worth noting that this protective effect is directly related to the phytochemical compounds present in noni oil. The compounds have the action of inducing a fungistatic effect on the structure of the fungus, thus preventing the progress of the disease, as well as the action of inducing the defense mechanism of plants and fruits.

Benato et al. (2018) observed the preventive effect of cinnamon and lemongrass essential oil in controlling green mold disease in oranges. It found that lemongrass at a concentration of 0.5 g L-1 showed a reduction in the AACPD value by 53% when compared to the control. This confirms that essential oils are phytochemical compounds with great potential for protective and preventive action against certain fungal diseases.

The protective effect found in microorganisms such as the yeast S. cerevisiae may be related to their ability to produce volatile organic compounds that can help protect the fruits. There is also the possibility of competition for space among other factors that should be better studied.

Ferreira (2020), verified the action of an antifungal compound (unidentified) produced by yeast Hansenula wingei in controlling the blue rot disease in apple fruits. The author confirmed the preventive efficacy of the compound in fruits, which significantly controlled the severity of the disease in post-harvest fruits by 61.52%.

The literature also reports several scientific studies confirming the protective potential of S. cerevisiae in other fruits affected by fungal diseases. As well as the protective potential presented by other yeast species.

Da Cunha et al. (2018) studied the curative and preventive potential of the yeast Candida stellimalicola in protecting orange fruits against blue mold. According to the authors, when applied preventively, yeast reduces the severity of the disease by more than 90%, controlling blue mold on orange fruits. Furthermore, the authors add that the ideal would be to apply the yeast pre-harvest, this way, it can offer better protection to the fruits in relation to the action of pathogens that occur post-harvest.

Heling et al. (2017) evaluated the potential of S. cerevisiae to control Colletotrichum musae in bananas. Satisfactorily, the authors report that yeast as a treatment reduced the progress of the disease by 48% and state that the microorganism is a potential agent in the control of Colletotrichum musae.

5. Conclusion

From the above, it can be concluded that, among the main causal agents of diseases in the post-harvest of citrus are the fungi Penicillium sp, Guignardia sp and Aspergillus sp. It was found that the major compound present in noni essential oil is octanoic acid. It was found that noni essential oil showed fungitastic activity at the highest concentration of 30 mg mL-1 only for the fungus Penicillium sp, Guignardia sp. In contrast, the fungitastic potential of the yeast S. cerevisiae was observed for the pathogens Penicillium sp. and Aspergillus sp. with inhibition of 88% and 100% at the highest concentration (5%). Noni essential oil did not show phytotoxicity in citrus fruits. And the preventive potential of noni oil and S. cerevisiae was achieved in both treatments, with the yeast S. cerevisiae being the highlight, which showed 100% protection in all fruits tested. The study proved the fungal potential of Morinda citrifolia and S. cerevisiae in controlling pathogenic fungi in post-harvest citrus. It aimed to study a new bioproduct in order to contribute to a sustainable and biologically correct environment in terms of food quality and alternative control.

Acknowledgements

Thank Capes for providing the scholarship and the Federal University of Tocantins (UFT) for the structure and availability of laboratories for the development of research.

Data Availability Statement

The entire data set that supports the results of this study was published in the article itself.

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Edited by

  • Editor:
    Takako Matsumura Tundisi

Publication Dates

  • Publication in this collection
    13 Oct 2025
  • Date of issue
    2025

History

  • Received
    19 Feb 2025
  • Accepted
    01 Aug 2025
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