Antifungal Efficacy of Plant Extracts against Fungal Pathogens Associated with Postharvest Rot in Cocoyam

Antifungal Efficacy of Plant Extracts against Fungal Pathogens Associated with Postharvest Rot in Cocoyam

Nji Griphan Fru¹*, Onyeche Vange² and Ayeoffe Fontem Lum³

¹Centre for Food Technology and Research, Department of Biological Sciences, Benue State University, Makurdi, Benue State, Nigeria

²Department of Crop and Environment, Joseph Sarwuan Tarka University, Makurdi, Benue State, Nigeria

³Kings University, Odeomu, Osun State, Nigeria

*Corresponding Author

DOI: https://doi.org/10.51584/IJRIAS.2025.100700005

Received: 27 June 2025; Accepted: 02 July 2025; Published: 26 July 2025

ABSTRACT

Fungal pathogens affecting stored cocoyam are estimated to result in over 40% post-harvest and financial losses for cocoyam farmers in Sub-Saharan Africa. A study was conducted to isolate and identify fungal organisms responsible for postharvest rot of cocoyam corms during storage, as well as to assess the fungicidal efficacy and mycelia growth inhibitory effects in vitro of plant extracts from Black pepper (Piper nigrum), Neem (Azadirachta indica), and Alligator pepper (Aframomum melegueta) against fungi associated with cocoyam rot in storage. Cocoyam corms exhibiting signs of rot were retrieved from storage to isolate fungal pathogens. Fresh, healthy cocoyam corms were also used to assess the pathogenicity of the isolated fungi. The fungicidal capacity of the aqueous plant extracts was assessed using three extract concentrations (10% w/v, 20% w/v, and 30% w/v). Means were separated using Duncan Multiple Range Test, and analysis of variance was utilized for analysing the data at the 95% confidence level. All fungal pathogens isolated caused rot in both varieties of healthy cocoyam corms following a 14-day inoculation period. Rhizopus stolonifer and Bipolaris sp caused 73.33% rot severity each, followed by Aspergillus flavus (60.0%), Colletotrichum gloeosporioides (33.33%) and Botryodiplodia theobromae (26.67%). The highest radial growth inhibition (90.0%) was recorded for 30% w/v Alligator pepper on Rhizopus stolonifer and 30% w/v black pepper on Bipolaris spp. Alkaloids, tannins, phenols, saponins, flavonoids, cardiac glycosides terpenoids, and Phytosterols were found in the crude aqueous plant extracts. Aqueous extracts of Alligator pepper, Black pepper, and Neem significantly (P ≤ 0.05) inhibited the mycelia growth of fungal pathogens in vitro and can also be used as a substitute for conventional fungicides.

Keywords: Cocoyam varieties, Fungi pathogens, Pathogenicity, Plant extracts, Antifungal

INTRODUCTION

Cocoyam, a perennial herbaceous monocotyledonous plant belongs to the Araceae family. Xanthosoma sagittifolium (the white type or tannia) and Colocasia esculenta (the red type or taro) are the two most widely grown species (Onyeka, 2014; Bartholomew et al. 2017; Fru and Vange, 2023). The production of cocoyam in Sub-Saharan Africa is primarily carried out by resource-poor, small-scale farmers with limited agricultural input (Bartholomew et al. 2017). In Nigeria, cocoyam is the third most important root and tuber crop that is grown and consumed after cassava and yam, and it is superior in terms of nutrition to cassava and yam regarding minerals and digestible crude protein (Ca, Mg, and P) contents (Green, 2003; Chukwu et al. 2008; Ezeonu et al. 2018). Nutritionally, it has high carbohydrate content (13 – 29%), proteins (1.4 – 3.0%), vitamins, and minerals. More than 60% of the world’s cocoyam production comes from Cameroon, Ghana, and Nigeria (Onyeka, 2014; Fru et al. 2024).

Cocoyam corm decay and loss during storage in Nigeria is primarily as a result of microbial action with an estimated 40 – 50% loss (Eze and Maduewesi, 1990). According to Chukwu et al. (2008), sprouting, rots and other physiological changes during cocoyam storage resulted in roughly 50% economic losses after two months and after five months, approximately 95%. Rot is the softening of the plant parts brought on by a proteolytic enzyme that the pathogen secretes into the plant tissues, dissolving the plant parts or fruits (Akueshi et al. 2002). Rot pathogens that have been isolated from corms of C. antiquorum, C. esculenta, and X. sagittifolium during storage in Nigeria include F. salani, B. theobromae, F. oxysporium, S. rolfsii, Fusarium sp, and R. stolonifer. According to reports, these fungal pathogens are also the main causes behind storage rots in other root and tuber crops, including sweet potatoes, yams, and cassava (Amienyo & Ataga, 2006; Banito et al. 2010; Okigbo et al. 2010; Eze & Ameh, 2011). Rapid and pervasive host tissue degradation leads to quantitative pathogenic losses of stored cocoyam. The pattern of attack generally consists of one or a few peculiar pathogenic or saprophytic organisms growing on the decomposing moribund tissues left over from the initial infection, which results in wounds from harvest bruises and the places where the corms have detached (Eze and Ameh, 2011).

To combat the possible risks and pollution issues related to the use of synthetic chemicals, the use of biopesticides derived from plants has been proposed as an alternative to chemical use (Amadioha and Obi, 1998; Amadioha, 2000). According to Iwuagwu et al. (2018), fungicidal plants are highly effective at preventing fungal growth both in vitro and in vivo. Neem (Azadirachta indica), black pepper (Piper nigrum), and alligator pepper (Afromomum meleguata) are among plants with anti-fungi properties and potential alternatives to control and prevent cocoyam decay during storage.  This study aimed to isolate and identify fungi associated with the postharvest decay of cocoyam corms in storage, evaluate the pathogenicity of the isolated pathogenic fungi, and assess the efficacy of organic plant extracts of Neem (Azadirachta indica), Black pepper (Piper nigrum), and Alligator pepper (Afromomum melegueta) in inhibiting the radial growth of fungi pathogens in vitro and identifying the phytochemicals found in the plant extracts.

MATERIALS AND METHODS

Sources of Cocoyam Corm

A total of 50 rotten cocoyam corms were randomly collected from a cocoyam storage study conducted at Benue State University, Makurdi, Nigeria. The collected diseased corms were taken to the Biological Sciences Laboratory in the University for further Studies. Twenty-four (24) freshly harvested corms of Colocasia esculenta (taro) and Xanthosoma sagittifolium (tannia) were each obtained from local farms

Sterilization

Petri dishes, beakers, volumetric flasks, cork borer, test tubes, and other glass wares were sterilized for an hour at 160⁰C in a hot air oven. Sterilisation of the wire loops was done by burning them until red hot using a Bunsen burner and letting them cool. The work surfaces were cleaned with 70% alcohol to avoid contamination.

Media Preparation

The isolation media utilised was potato dextrose agar (PDA). The culture medium was prepared according to the manufacturer’s instructions by dissolving 39g of media in 1L of sterile distilled water. The solution was heated using a heating mantle and aseptically sterilized using an autoclaved at 121⁰C at 15 psi for 15 minutes, and then let to cool (42 – 45⁰C). The antibiotic chloramphenicol was added to the culture medium and mixed thoroughly before it was poured into sterilized Petri dishes to prevent bacteria growth.

Isolation of Fungal Pathogens from Cocoyam Corms

Mahmoud and Al-Ani (2016) isolation methods were applied. Using a sterile knife, pieces of diseased tissues (3 x 2 mm) were cut off the outside of decaying cocoyam corms. They were then surface-sterilized for one minute in a 5% sodium hypochlorite (NaOCl) solution. After being surface sterilised, they were rinsed three times with distilled sterile water and dried in a sterile Lamina flow chamber before being plated on a PDA medium that had hardened and been modified with chloramphenicol. The inoculated plates were incubated at room temperature and observed for microbial growth. Mycelia growth was observed for 3 – 5 days and pure cultures were obtained through sub-culturing. Pure cultures were obtained by several transfers of each growth colony from PDA plates containing previously cultured fungi (Liamngee et al. 2015). Using the formula used by Fayinminu et al. (2025), the occurrence of each isolated fungal pathogen was calculated by dividing the frequency of each fungus by the total number of fungi on each plate and the result was then reported as a percentage.

Percentage of Occurrence =

Identification of Fungal Isolates

Macroscopic and microscopic analyses of the growth morphology of the fungi were used to identify pure cultures (Terna et al. 2019). On the Petri plates, colony traits like appearance, change in medium colour, and growth rate were noted for macroscopic identification. Lactophenol cotton blue dye was used to produce slide mounts of the isolates for microscopic inspection, which was then conducted under a microscope. Barnett and Hunters (1985) and Marthur and Kongsdal (2003) Standard Fungi Manuals were consulted in order to compare the isolates that were observed.

Pathogenicity Test

The pathogenicity test was conducted using the Okigbo and Ikediugwu (2000) approach. Soil and debris were removed from healthy cocoyam corms by washing them with tap water. The corms were rinsed with sterile distilled water after being surface sterilised for 2 minutes with 1% sodium hypochlorite, and air dried. 1cm deep holes were bored from the tip of healthy cocoyam corms using a 5mm sterile cork borer. 7 – days – old cultures of each fungus were inserted into the holes in the corms, and the cocoyam cores from the corm were reinstalled after parts had been removed. A sterile PDA disc was used in place of the culture discs to serve as the control. No fungus was placed in the control. Each fungus was replicated four times in a completely randomized design. The inoculated corms were incubated for 14 days at room temperature (28 ± 2^oC). The same procedure was used for the control except that discs of un-inoculated PDA were placed in the holes created in the corms (Amienyo and Ataga, 2006).

Assessment of Cocoyam Corm Tissue Rot

Using a sterile knife, the inoculated corms were cut open at right angles along the inoculation points at the conclusion of the 14-day incubation period to yield identical halves. Morphological characteristics and growth patterns were observed in each case and compared with those of the original isolates for infection and disease development (Fatimoh et al. 2017; Liamngee et al. 2018).

Disease incidence

Disease incidence in corms was calculated as shown by Liamngee et al. (2015).

Disease incidence % (DI) = (number of infected corms)/(total number of corms sampled)×100

Disease severity

The corm disease severity was assessed on a scale of 0 – 5 as described by Bdliya and Langerfeld, (2005), where;

0 = no symptom of rot

1 = 1–15% of corm rotten

2 = 16–30% of corm rotten

3 = 31–45% of corm rotten

4 = 46–60% of corm rotten

5 ≥ 61% of corm rotten

The disease severity was computed using the formula

Disease severity % (DS) =∑(a+b)/(N.Z) X 100

Where: Ʃ (a + b) = Sum of symptomatic corms and their corresponding score scale

N = Total number of cocoyam corms assessed

Z = highest score scale on the severity scale.

Measurement of rot

The extent of the rot was determined by calculating the area of rot using the formula adopted by Ezeibekwe and Ibe (2010). The diameter and depth of the rot were measured using a transparent ruler that had been sterilised. By deducting the initial depth (1 cm) from the end depth, the true depth was got.

Where: d = diameter

             L = depth

            ∏ = 22/7 (Constant)

Preparation of Aqueous Plant Extracts

Seeds of Aframomum melegueta (Alligator pepper) and Piper nigrum (Black pepper) were sourced from Wadata Market, Makurdi, and fresh leaves of Azadirachta indica (Neem) were harvested from Benue State University campus. The fresh neem leaves were washed separately under a gentle stream of tap water to remove surface dirt, then in sterile distilled water containing 1% sodium hypochlorite for 2 minutes and air dried for 7 days before milling.

The seeds of A. melegueta, P. nigrum, and A. indica leaves were finely ground into powder using a blender. Extracts of A. melegueta, P. nigrum, and A. indica were obtained by adding each powder (100g, 200g, and 300g) to 1000 ml of sterile distilled water in 1000 ml conical flasks using the cold solvent extraction method as described by Nweke (2015) and Fru & Vange (2023). Each suspension was manually shaken for 2 minutes and allowed to stand for 24 hours before being filtered into a fresh flask using a four-fold sterile muslin cloth.

In Vitro Efficacy of Plant Extracts on the Radial Growth of Isolated Fungi Pathogens

The antifungal activities of the different plant extracts were evaluated using the poisoned food method described by Lum et al. (2019) with slight modifications in which 2 ml of each plant extract was added to 15 ml of PDA on Petri dishes and each plate was gently swirled on the laboratory bench to ensure even dispersion of extracts to give a PDA-extract mixture. The mixture was permitted to solidify prior to inoculation at the center of each plate with 4 mm diameter mycelia taken from the colony edge of pure cultures the isolated fungi (7 days old). Three replicates of each treatment were used in the control experiment, which involved inoculating sterile PDA with sterile distilled water containing the identified fungal pathogen.

Using a transparent meter rule, the radial growth diameters of the test fungi were measured in centimetres (cm) at 3, 5, and 7 days after the inoculated plates had been incubated at ambient temperature. The mean growth in two directions along two perpendicular lines drawn on the back of the plates was used to calculate the colony diameter. With minor adjustments, the formula of Ndifon and Lum (2021) was used to determine the inhibition of fungal growth by plant extracts.

Percentage Inhibition =(Rc-Rt)/Rc × 100

Where Rc = Radial growth diameter of the pathogen in control

Rt = Radial diameter of the pathogen in PDA-Extract plates

The scale outlined by Okigbo et al. (2015) was adopted to rate the extracts inhibitory effects;

0 % inhibition          = Not effective

1 – 19 % inhibition = Slightly effective

20 – 49% inhibition = Moderately effective

50 – 99% inhibition = Effective

100 % inhibition      = Highly effective

Phytochemical Analysis of Plant Extracts

Phytochemical analysis was carried out on part of the pulverized plant materials to reveal the presence of secondary metabolites in them using the method of Fru and Vange, (2023).

Data Analysis

Analysis of variance (ANOVA) was performed on the data collected using SPSS. Using Duncan Multiple Range Test (DMRT), treatment means were separated at a 5% probability level.

RESULTS AND DISCUSSIONS

Isolation, Identification, and Pathogenicity of the Fungi Causing Decay During Storage

The fungi pathogens isolated from the stored rotten cocoyam corms and their percentages of occurrence were Colletotrichum gloeosporioides (22.45%), Rhizopus stolonifer (11.57%), Bipolaris sp (33.33%), Botryodiplodia theobromae (17.69) and Aspergillus flavus (14.97%) as shown in Tables 1 and 3. This agrees with Anukworji et al. (2012) who identified most of these species in a study on isolation of fungi causing rot of cocoyam. Other fungi pathogens associated with cocoyam rot in Nigeria include Aspergillus flavus, Penicillium digitatum, Botryodiplodia theobromae, Sclerotium rolfsii, Fusarium solani, F. oxysporium, Botrytis spp, Pithium spp, Phytophthora colocasia, Rhizoctonia bunoides and Erwinia carotovora (Brunt et al. 2001). Some of these pathogens have also been isolated from yam (Okigbo et al. 2015; Ndifon and Lum, 2021; Ndifon and Lum, 2023).

The pathogenicity test revealed that all the isolated pathogens could induce rot in healthy cocoyam corms though, at various percentages of severity, mean area of rot caused after 14 days of inoculation as shown in Tables 2 and 4. The most virulent fungi pathogens were Rhizopus stolonifer and Bipolaris sp causing 73.33% rot each followed by Aspergillus flavus (60.0%) and Colletotrichum gloeosporioides (33.33%). The least virulent was Botryodiplodia theobromae inducing 26.67% rot in infected tissue. The un-inoculated cocoyam corms in the control units showed no signs of decay after 14 days. This is in agreement with the reports of many researchers on cocoyam corms (Offei, 1999; Eze and Ameh, 2011; Anukworji et al. 2012; Ezeonu et al. 2018). The isolation of more than one fungal pathogen from a particular corm affirms the possibility of multiple infections whose combined effect may cause rapid rotting of the cocoyam corms and this agrees with the reports of Anukworji et al. (2012) and Okigbo et al. (2015) on cocoyam and yam respectively. The ability of the fungal isolates to cause infection in healthy cocoyam corms was because the pathogens can utilize the nutrients from the corms as a substrate for growth and development (Liamngee et al. 2015). Thus, it is recommended to use the area method to measure the extent of pathogenic fungal damage to cocoyam corms and other root and tuber crops. The degree of severity of the mean area rot of Colocasia esculenta was significantly higher than the mean area rot of Xanthosoma sagittifolium.

Table 1: Percentage Occurrence of the Fungi Isolates from the Rotten Cocoyam Corms

Table 2: Incidence of decay and rot severity on healthy cocoyam corms inoculated with the test fungi

**significant at 1% level of probability and *significant at 5% level of probability

Table 3: Characterization of fungal isolates from decaying cocoyam corms during storage

Macroscopic characteristics	Microscopic characteristics	Appearance on PDA	Photomicrograph	Probable organisms
Pinkish mycelia colour with a cottony-like structure and traces of whitish cream colouration around the edges	Cylindrical-shaped conidia with a septum, single cell, hyaline, and a smooth round end			Colletotrichum gloeosporioides
Fast-growing colonies with cotton fluffy colouration becoming greyish-brown with time.	Non-septate sporangiospores are hyaline, smooth-walled, simple, or branched forming large terminal globose sporangium			Rhizopus stolonifer
The colony colour started as an effuse white cottony-like structure and the colour later turned to grey and finally turned to blackish brown.	Curved conidia with septate hyphae			Bipolaris sp
Growth began as white aerial filamentous mycelia with a grey centre. Colony turned grey and then dark grey to black as days progressed.	Conidia were ellipsoid in shape, thick-walled, and hyaline.  Spores were aseptate when immature but matured into 2-celled dark-brown spores			Botryodiplodia theobromae
The colony was a dense felt yellowish-green colouration. Mycelia growth was usually in concentric rings.	Conidia bluish green in nature with smooth long and hyaline conidiophores.			Aspergillus flavus

Table 4: Rot Types and Mean Area (cm²) of rot caused by each pathogenic fungus after 14 days of inoculation on cocoyam varieties

In Vitro Efficacy of Plant Extracts on the Radial Growth of Isolated Fungi Pathogens

The results of this study demonstrated the presence of fungi-toxic substances in the seeds of alligator pepper, black pepper, and neem leaves since they were capable of inhibiting the mycelia growth of the pathogenic fungi of cocoyam. The findings are consistent with previous reports of other studies, but with different fungal diseases and crops (Okigbo et al. 2009; Doherty et al. 2010; Nweke, 2015; Ezeonu et al. 2018; Gwa and Ekefan, 2018; Bamidele, 2019; Lum et al. 2019). However, the efficiency of the extracts differed with plant material, concentration, and each test fungus. The difference observed in fungi-toxic activity of the extracts is likely due to the solubility of the active compound(s) in water or the presence of inhibitors to the fungi-toxic principle. This also agrees with the report of Amadioha (2001) and Okigbo and Ogbonnaya (2006).

Mycelia growth inhibition of Colletotrichum gloeosporioides  

The radial growth of C. gloeosporioides in vitro was significantly suppressed by the synthetic fungicide (Mancozeb) and the different aqueous plant extracts used in the study at different concentrations. 30% w/v extract concentration (85.39%) proved to be the most fungi-toxic on C. gloeosporioides while the least inhibitory effect was observed at 10% w/v extract concentration (82.20%). This agrees with  Anukworji et al. (2012) who stated a significant difference between mycelia growth values recorded on the various plant extract concentrations. Colletotrichum gloeosporioides was significantly susceptible to the synthetic fungicide (Mancozeb) followed by Alligator pepper, Neem, and Black pepper with the least radial growth inhibition as shown in Table 5. This result agreed with the findings of Amienyo and Pandukur (2016) on the isolation of post-harvest fungi of cocoyam. Mancozeb at 8g/L (88.53%) significantly had the highest inhibitory effect on C. gloeosporioides in vitro compared to Neem at 10% w/v (79.67%) with the least inhibitory effect.

Table 5: Main effects of concentrations and plant extracts on percentage mean radial growth  inhibition on Colletotrichum gloeosporioides after inoculation

Table 6: Interaction effects of concentrations and plant extracts on percentage mean radial growth inhibition on Colletotrichum gloeosporioides after inoculation

Mycelia growth inhibition of Rhizopus stolonifer

Mancozeb and the different plant extracts used in the study at different concentrations were very effective in the inhibition of mycelia growth of R. stolonifer in vitro. Mancozeb gave the highest radial growth inhibitory effect on Rhizopus stolonifer by 91.53%, followed by the aqueous extract of Alligator pepper with 89.23% while aqueous extracts of Black pepper and Neem showed the least mycelia growth inhibition of 88.21% and 86.69% respectively as shown in Table 7. Similar results with Bibah (2014) and Ezeonu et al. (2018) showed that plant extracts were very effective in inhibiting the mycelia growth of R. stolonifer. The efficacy of the interaction of aqueous plant extracts and concentration in inhibiting R. Stolonifer was significantly different from Mancozeb at 8g/L (93.07%) with the highest inhibitory effect and Neem at 30% w/v (84.63%) with the least inhibitory effect as shown in Table 8.

Table 7: Main effects of concentrations and plant extracts on percentage mean radial growth  inhibition on Rhizopus stolonifer after inoculation

Table 8: Interaction effects of concentrations and plant extracts on percentage mean radial growth inhibition on Rhizopus stolonifer after inoculation

Mycelia Growth Inhibition of Bipolaris sp

The radial growth of Bipolaris sp in vitro was significantly (P ≤ 0.05) suppressed by Mancozeb and the different aqueous plant extracts used in the study at different concentrations. 30% w/v concentration (88.05%) was fungi-toxic on Bipolaris sp while the least inhibitory effect was observed at 10% w/v concentration (81.11%) as shown in Table 9. This agrees with  Anukworji et al. (2012) and Hasan et al. (2012) who observed significant differences between mycelia growth values recorded for the various plant extract concentrations. Bipolaris sp was more susceptible to Mancozeb (100.00%) followed by Black pepper (86.96%), Neem (84.71%), and Alligator pepper (81.91%) with the least radial growth inhibition. Similar results with Hasan et al. (2012); Prashith Kekuda et al. (2016), and Elsherbiny et al. (2017) showed that plant extracts were very effective in inhibiting mycelia growth of Bipolaris sp. Mancozeb at 8g/L (100.00%) and Mancozeb at 4g/L (100.00%) had the highest mycelia growth inhibitory effect of Bipolaris sp compared to Alligator pepper at 10% w/v (75.83%) with the least inhibitory effect as shown in Table 10.

Table 9: Main effects of concentrations and plant extracts on percentage mean radial growth inhibition on Bipolaris sp after inoculation

Table 10: Interaction effects of concentrations and plant extracts on percentage mean radial growth inhibition on Bipolaris sp after inoculation

Mycelia Growth Inhibition of Botryodiplodia theobromae

Fungi-toxic activities of the aqueous plant extracts increased with an increase in concentration against B. theobromae. 30% w/v (82.53%) proved to be the most effective while the least inhibitory effect was observed at 10% w/v (75.92%) on B. theobromae. This supports previous studies by Anukworji et al. (2012), Amienyo and Pandukur (2016), and Gwa and Ekefan (2018). The study showed that Mancozeb (100.00%) was highly effective against mycelia growth of B. theobromae while extracts of Alligator pepper (71.30%) were least effective among the extracts in vitro as shown in Table 11. This is similar to the results obtained by Anukworji et al. (2012) who reported a highly effective inhibition of A. niger, F. solani, S. rolfsii, and B. theobromae with aqueous plant extracts of C. papaya, G. kola, A. sativum, and A. indica. This study showed that B. theobromae is more susceptible to Mancozeb at 8g/L (100.0%) and Mancozeb at 4g/L (100.0%), but less susceptible to aqueous extracts of Neem at 10% w/v (70.50%), Alligator pepper at 10% w/v (70.43%), and Alligator pepper at 20% w/v (68.87%) as shown in Table 12.

Table 11: Main effects of concentrations and plant extracts on percentage mean radial growth inhibition on Botryodiplodia theobromae after inoculation

Table 12: Interaction effects of concentrations and plant extracts on percentage mean radial growth inhibition on Botryodiplodia theobromae after inoculation

Mycelia Growth Inhibition of Aspergillus flavus

The radial growth of A. flavus in vitro was significantly suppressed by Mancozeb and the different aqueous plant extracts used in the study at different concentrations. 30% w/v (85.22%) extract concentration proved to be the most fungi-toxic on A. flavus while the least inhibitory effect was observed at 10% w/v (82.09%) extract concentration after 7 days of incubation as shown in Table 13. The results are in agreement with the reports of many researchers like Anukworji et al. (2012) and Sulaiman et al. (2019) who stated a significant difference between mycelia growth values recorded in the various concentrations. Aspergillus flavus was more susceptible to the Mancozeb (87.62%) and Alligator pepper (85.59%), with Neem (82.91%) and Black pepper (82.79%) having the least fungi-toxic effect. These results agree with the findings of Okigbo and Nmeka, (2005) on the control of yam tuber rot with leaf extracts. The most significant fungi-toxic effects on the interaction between concentration and extracts were observed with Mancozeb at 4g/L (88.20%) compared to Neem at 10% w/v (78.97%) with the least fungi-toxic effect on A. flavus as shown on Table 14. The presence of antifungal substances in the different aqueous plant extracts which caused mycelia growth inhibition of fungi pathogens in vitro agrees with reports of other researchers (Okigbo and Nmeka, 2005; Anukworji et al. 2012; Okigbo et al. 2015; Amienyo and Pandukur, 2016; Sulaiman et al. 2019).

Table 13: Main effects of concentrations and plant extracts on percentage mean radial growth  inhibition on Aspergillus flavus after inoculation

Table 14: Interaction effects of concentrations and plant extracts on percentage mean radial growth inhibition on Aspergillus flavus after inoculation

Phytochemical Analysis of Plant Extracts

Results of the qualitative phytochemical screening of aqueous plant extracts of Alligator pepper (Aframomum melegueta), Black pepper (Piper nigrum), and Neem (Azadirachta indica) are shown in Table 15. Phytochemical analysis of aqueous plant extracts revealed the presence of alkaloids, tannins, phenols, saponins, flavonoids, cardiac glycosides terpenoids, and Phytosterols. The fungicidal and pharmacological potential of all these phytochemicals were proven by the report of several works (Okigbo et al. 2009; Ezeonu et al. 2019; Fru and Vange, 2023). Phytochemical screening of Black pepper extract by Aghale et al. (2017) indicated the presence of alkaloids, flavonoids, saponins, tannins, and phenols. The phytochemical analysis of Alligator pepper by Doherty et al. (2010) revealed the presence of tannin, saponin, flavonoid, steroid, terpenoids, cardiac glycoside, alkaloid, and phenols.

Table 15: Phytochemicals present in the plant extracts

–  = Absent                     + = Present                         ++ = Highly present

CONCLUSION

This study identified Colletotrichum gloeosporioides, Rhizopus stolonifer, Bipolaris sp, Botryodiplodia theobromae, and Aspergillus flavus as the main fungi pathogens responsible for causing postharvest losses to cocoyam varieties during storage in Makurdi. Pathogenicity test and mean area of rot confirmed the ability of the isolated pathogens to induce rot, with Rhizopus stolonifer and Bipolaris sp causing the highest severity. Results obtained from phytochemical screening of the aqueous extracts of Alligator pepper, Black pepper, and Neem confirmed their anti-microbial potency and their use in disease control. Due to their ability to considerably limit the growth of fungal pathogens in vitro, this study demonstrated that the various aqueous plant extracts had fungi-toxic compounds. Notably, the plant extracts were shown to be just as effective as the conventional synthetic fungicide, and more effective in many instances. This indicates that the plant extracts possess naturally active antimicrobial components. Considering matrices of performance parameters it can be concluded that black pepper extract is the most effective of the three plant extracts and 30% w/v was the most effective concentration of the different plant extracts. The botanicals can be used commercially as an alternative to synthetic fungicide due to their availability, accessibility, and affordability as safe treatment in a sustainable organic post-harvest management system.

REFERENCES

1. Aghale, D.N., Egbucha, K.C. & Umeh, O.J. (2017). Evaluation of some plant extracts on the control of fungi infestation on yam in storage. Nigerian Journal of Agriculture, Food and Environment, 13(2), 148–152.
2. Akueshi, C.O., Kadir, C.O., Akwueshi, E.U., Agina, S.E. & Ngurukwem, C. (2002). Antimicrobial potential of Hytissau veoleus Poit (Laminaceae). Nigerian Journal of Botany, 15, 37–41.
3. Amadioha, A.C. and Obi, V.C. (1998). Fungitoxic activity of Azadirachta indica and Xylopica on Collectotrichum lindemuthianum. Journal of Herbs Spices and Medicinal Plants, 6, 33–40.
4. Amadioha, A.C. (2000). Controlling rice blast in vitro and in vivo with extracts of Azadirachta indica. Crop Protection, 19, 287–290.
5. Amadioha, A.C. (2001). Fungitoxic effects of some leaf extracts against Rhizopus oryzae causing tuber rot of potato. Archieves of Phytopathology and Plant Protection, 33(6), 499–507.
6. Amienyo, C.A., & Ataga, A.E. (2006). Post harvest fungal diseases of sweet potato (Ipomoea batatas L. Lam) tubers sold in selected markets in Rivers state, Nigeria. Science Africa, 5(2), 95–98.
7. Amienyo, C.A., & Pandukur, S.G. (2016). Effect of Azadirachta indica extract on the radial growth of some test fungi isolated from two varieties of cocoyam (Colocasia esculenta L.) corms and cormels in some markets in Plateau State, Nigeria. Journal of Phytopathology and Pest Management, 3(1), 46–59.
8. Anukworji, C.A., Putheti, R.R., & Okigbo, R.N. (2012). Isolation of fungi causing rot of cocoyam (colocasia esculenta L. schott) and control with plant extracts : (Allium sativum, Garcinia kola, heckel, Azadirachta indica, and Carica papaya). Global Advanced Research Journal of Agricultural Science Vol., 1(1).
9. Bamidele, H.O. (2019). Antifungal potency of Aframomum melegueta (Alligator Pepper) seed extracts on postharvest rot fungi of two Citrus Species. Sustainable Food Production, 6, 1–11. https://doi.org/10.18052/www.scipress.com/sfp.6.1
10. Banito, A. Kpumoua, K.E.; Bissang, B, and Wydra, K. (2010). Assessment of cassava root ands stem rots in ecozones of Togo and evaluation of the athogen virulence. Journal Bot., 42(3), 2059–2068.
11. Barnett, H. & Hunters, B. (1985). Illustrated Genera of Imperfect Fungi (4th Editio). Macmillan Incorporation.
12. Bartholomew, N.A., Emylia, J.T., & Chibuzor, N. (2017). Preventive and curative control of sclerotium rot disease of cocoyam cormel (Colocasia esculenta L. Scott) using plant extracts and Trichoderma koningii. Journal of Applied Biology & Biotechnology, 5(6), 40–44. https://doi.org/10.7324/jabb.2017.50606
13. Bdliya, B.S., & Langerfeld, E. (2005). Soft rot and Blackleg (Erwinia carotovora) of potato as affected by inoculum density and variety. Nigerian Journal of Plant Protection, 22, 65–75.
14. Bibah, L. (2014). Efficacy of organic extracts. Doctoral Dissertation. Kwame Nkrumah University Of Science And Technology Kumasi College, Ghana.
15. Brunt, J., Hunter, D. & Delp, C. (2001). A Bibliography of Taro Leaf Blight. Secretariat of the Pacific Community (SPC) AusAID Taro Genetic Resources: Conservation and Utilization. Noumea, New Caledonia, 93.
16. Chukwu, G.O.C., Nwosu, K.I., Madu, T.U., Chinaka, C. & Okoye, B.C. (2008). Development of gocing storage method for cocoyam. Munich Personnel RePEc Archives (MPRA), 25, 17444.
17. Doherty, F.V., Olaniran, O.O. & Kanife, U.C. (2010). Antimicrobial Activities of Aframomum melegueta (Alligator Pepper). International Journal of Biology, 2(2), 126–131. https://doi.org/10.5539/ijb.v2n2p126
18. Doughari, J.H., Elmahmood, A.M. & Manzara, S. (2007). Studies on the antibacterial activity of root extracts of Carica papaya L. African Journal of Microbiology Research, 1(3), 37–41.
19. Elsherbiny, E.A., Safwat, N.A., & Elaasser, M.M. (2017). Fungitoxicity of organic extracts of Ocimum basilicum on growth and morphogenesis of Bipolaris spp. Journal of Applied Microbiology, 123(4), 841–852. https://doi.org/10.1111/jam.13543
20. Eze, C.S. & Maduewesi, J.N.C. (1990). Relation of traditional methods to the magnitude of storage losses of cocoyam (Colocasia esculenta (L.) Schott). Nigerian Journal of Plant Protection, 13, 26–34.
21. Eze C. S. & Ameh, G. I. (2011). Comparative assessment of pathogenicity of storage rot causing fungi of Cocoyams (Colacasia esculenta (L.) Schott) and their host-pathogen interactions. Nigerian Journal of Biotechnology, 22, 23–27.
22. Eze, S.C. (1984). Studies on storage rot of cocoyam (Colocasia esculenta (L.) Schott). M.Sc Dissertation. Deptartment of Botany, University of Nigeria, Nsukka, 73.
23. Ezeibekwe, I.O. & Ibe, A.E. (2010). Fungal organisms associated with Yam (Dioscorea rotundata, Poir) rot at Owerri,Imo State of Nigeria. Journal of Molecular Genetics, 2(1), 1–5.
24. Ezeonu, C.S., Tatah, V.S., Imo, C., Mamma, E., Mayel, M.H., Kukoyi, A.J., & Jeji, I.A. (2019). Inhibitory effect of aqueous and ethanolic extracts of Neem parts on fungal rot disease of Solanum tuberosum. Pakistan Journal of Biological Sciences, 22(5), 206–213. https://doi.org/10.3923/pjbs.2019.206.213
25. Ezeonu, C.S. Imo, C., Agwaranze, D.I., Iruka, A. Joseph, A. (2018). Antifungal effect of aqueous and ethanolic extracts of neem leaves , stem bark and seeds on fungal rot diseases of yam and cocoyam. Chemical and Biological Technologies in Agriculture, 5(1), 1–9. https://doi.org/10.1186/s40538-018-0130-3
26. Fatimoh, A.O., Moses, A.A., Adekunle, O.B., & Dare, O.E. (2017). Isolation and identification of rot fungi on post-harvest of pepper. Aascıt Journal of Biology, 3(5), 24–29.
27. Fayinminu, A.O., Liamngee, K., Gbira, T., Fru, N.G., Rekiya, Y., Mohammad, A., … Awua, D.T. (2025). Identification and pathogenicity of fungi causing postharvest decay of Irish Potato (Solanum tuberosum L.) tubers sold in Makurdi. Euroeean Journal of Ecology, Biology and Agriculture, 2(1), 1–13. https://doi.org/10.59324/ejeba.2025.2(1).01
28. Fru, N.G. and Vange, O. (2023). Efficacy of organic plant extracts on the post-harvest shelf life of cocoyam (Xanthosoma sagittifolium (L.) Schott) during storage. International Journal of Plant Pathology and Microbiology, 3(2), 84–90. Retrieved from https://www.plantpathologyjournal.com/archives/2023.v3.i2.B
29. Fru, N.G., Vange, O., Mzeyeche, D.S., & Kum, A.B. (2024). Effects of some indigenous organic plant extracts on the nutritional quality of stored cocoyam (Xanthosoma sagittifolium (L.) Schott). PROCEEDINGS OF 58TH ANNUAL CONFERENCE OF THE AGRICULTURAL SOCIETY OF NIGERIA Held at University of Abuja, Nigeria, 21-25 October, 2024, 3, 1280–1291.
30. Green, B. (2003). Taxonomic and nutritional analysis of certain tuber crops in the Niger Delta of Nigeria. African Journal of Environmental Studies, 4(1/2), 120–122.
31. Gulcin, I. (2005). The antioxidant and radical scavenging activities of black pepper (Piper nigrum) seeds. International Journal of Food Sciences and Nutrition, 56, 491–499.
32. Gwa, V.I. & Ekefan, E.J. (2018). Fungicidal effect of some plant extracts against tuber dry Rot of white yam (Dioscorea Rotundata Poir) caused by Aspergillus Niger. International Journal of Horticulture and Agriculture, 3(3), 1–7.
33. Hasan, M.M., Ahmed, F., Islam, M.R., & Murad, K.F.I. (2012). In vitro effect of botanical extracts and fungicides against Bipolaris sorokiniana, causal agent of leaf blotch of barley. Journal of Agroforestry and Environment, 6(1), 83–87.
34. Iwuagwu, C.C., Onejeme, F.C., Ononuju, C.C., Umechuruba, C.I., and Nwogbaga, A.C. (2018). Effects of plant extracts and synthetic fungicides on the radial growth of Phoma oryzae on rice (Oryza sativa L.) in some rice growing areas of South Eastern Nigeria. Journal of Plant Pathology and Microbiology, 9(12), 1–5. https://doi.org/10.4172/2157-7471.1000468
35. Junaid, S.A., Olabode, A.O., Onwuliri, F.C., Okwori, A.E.J., & Agina, S.E. (2006). The antimicrobial properties of Ocimum gratissimum extracts on some selected bacterial gastrointestinal isolates. African Journal of Biotechnology, 5(22), 2315–2321. https://doi.org/10.5897/AJB06.417
36. Liamngee, K., Akomaye, M.U., & Okoro, J.K. (2015). Efficacy of some botanicals in the control of fungi causing postharvest rot of yam in Katube market, Obudu, Nigeria. IOSR Journal of Pharmacy and Biological Sciences, 10(6), 33–34.
37. Liamngee, K., Iheanacho, A.C. & Kortse, P. A. (2018). Isolation , Identification and Pathogenicity of fungal organisms causing postharvest spoilage of tomato fruits during storage. Annual Research and Review in Biology, 26(6), 1–7. https://doi.org/10.9734/ARRB/2018/41804
38. Lum, A.F., Ndifon, E.M., Mbong, G.A., Chi, S J., & Ntsomboh-Ntsefong, G. (2019). Anti-fungal activity of plant extracts for the management of Fusarium oxysporum f. sp. elaiedis in vitro. International Journal of Biosciences (IJB), 15(6), 1–9. https://doi.org/10.12692/ijb/14.6.1-9
39. Mahmoud, S.N. & Al-Ani, N.K. (2016). Effect of different sterilization methods on contamination and viability of nodal segments of Cestrum nocturnum L. International Journal of Research Studies in Biosciences (IJRSB), 4(1), 4–9.
40. Marthur S.B. & Kongsdal, O. (2003). Common Laboratory Seed Health Testing Methods for Detecting Fungi (2nd Editio). International Seed Testing Association, Switzerland.
41. Ndifon, E.M. and Lum, A.F. (2021). Assessment of white yam tuber rot disease and in vitro management of Aspergillus niger in Ebonyi State, Nigeria. International Journal of Biosciences, 19(4), 32–40.
42. Ndifon, E.M. and Lum, A. F. (2023). Comparison of isolates of Phytophthora colocasiae Raciborski from diverse altitudes and appraisal of plant extracts for its management in vitro. FUDMA Journal of Agriculture and Agricultural Technology, 9(2), 40–45.
43. Nweke, F.U. (2015). Effect of Some plant leaf extracts on mycelia growth and spore germination of Botryodiplodia Theobromae causal organism of yam tuber rot. Journal of Biology, Agriculture and Healthcare, 5(8), 67–72.
44. Offei, M.A. (1999). Rotting of cocoyam (Xanthosoma sagittifolium (L.) Schott) cormels in storage: Aetiology and control. Master Thesis. Department of Crop Science Faculty of Agriculture University Of Ghana Legon.
45. Okigbo, R.N., Opara, P.U. & Anuagasi, C.L. (2015). Efficacy of extracts of water yam (Dioscorea alata) and aerial yam (Dioscorea bulbifera) peels in the control of white yam (Dioscorea rotundata) rot. Journal of Agricultural Technology, 11(8), 1823–1842.
46. Okigbo, R.N. & Ikediugwu, F.E.O. (2000). Studies in the biological control of postharvest rot of yams (Dioscorea rotundata) with Trichoderma viride. Journal of Phytopathology, 148, 331–335.
47. Okigbo, R.N. & Nmeka, L.A. (2005). Control of yam tuber rot with leaf extracts of Xylopia aethiopia and Zingiber offlcinale. African Journal of Biotechnology, 4(8), 804–807.
48. Okigbo, R.N; Agbata, C.A; and Echezona, C.E. (2010). Effect of leaf extract of Azadirachta India and Chromolaena odorata on post harvest spoilage fungi of yams in storage. Current Res J. of Soil Sci, 2(1), 9–12.
49. Okigbo, R.N. & Ogbonnaya, U.O. (2006). Antifungal effects of two tropical plant leaf extracts (Ocimum gratissimum and Aframomum melegueta) on postharvest yam (Dioscorea spp) rot. African Journal of Biotechnology, 5(9), 727–731.
50. Okigbo, R.N., Putheti, R. & Achusi, C.T. (2009). Post-Harvest deterioration of cassava and its control using extracts of Azadirachta Indica and Aframomum Melegueta. E-Journal of Chemistry, 6(4), 1274–1280. https://doi.org/10.1155/2009/680519
51. Onuegbu, B.A. (1999). Composition of four cocoyam cultivars and their tolerance to corm rot. Tropical Science, 39, 136–139.
52. Onyeka, J. (2014). Status of cocoyam (Colocasia esculenta and Xanthosoma spp) in West and Central Africa: production, household importance and the threat from leaf Blight. CGIAR Research Program on Roots, Tubers and Bananas (RTB)., 32.
53. Prashith, K.T.R., Akarsh, S., Noor, N., Ranjitha, M.C., Darshini, S.M., & Vidya, P. (2016). In vitro antifungal activity of some plants against Bipolaris sorokiniana (Sacc.) Shoem. International Journal of Current Microbiology and Applied Sciences, 5(6), 331–337. https://doi.org/10.20546/ijcmas.2016.506.037
54. Sulaiman, B., Hayatu, M., & Terna, T.P. (2019). Biocontrol potentials of selected plants against some post-harvest fungal. FUDMA Journal of Science, 3(2), 354–363.
55. Terna, T.P., Audi, Y. A., & Terna, F. C. (2019). Isolation and identification of fungi associated with stored sorghum (Sorghum bicolor L. Moench) seeds in Lafia, Nasarawa State, Nigeria. FUDMA Journal of Science, 3(1), 33–38.
56. Ugwuoke, K.I., Onyeke, C.C., & Tsopmbeng, N.G.R. (2008). The efficacy of botanical protectants in the storage of Cocoyam (Colocasia esculenta (L) Schott). Agro-Science. Journal of Tropical Agriculture, Food, Environment and Extension, 7(2), 93–98.