The document summarizes a study that investigated the effect of neem (Azadirachta indica) leaf extracts on the growth of Fusarium spp, a fungus that causes rot in stored kola nuts. Aqueous and ethanolic extracts of neem leaves at concentrations of 5-25% were tested against Fusarium spp in vitro. Both extracts significantly inhibited the radial growth of the fungus, with 20-25% concentrations exhibiting the highest inhibition of 82%. The ethanolic extracts showed greater inhibition at lower concentrations compared to aqueous extracts. This suggests that neem leaf extracts have potential as natural antifungal agents to help control rot fungus and extend the storage life of kola nuts.

1. International Journal of Tropical Agriculture and Food Systems, 4(1): 83-85, 2010
www.tapasinstitute.org/journals/ijotafs
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Tapas Institute of Scientific Research and Development, 2010
SHORT COMMUNICATION
EFFECT OF NEEM (AZADIRACHTA INDICA) LEAF EXTRACTS ON THE ROT
FUNGUS (FUSARIUM SPP) ISOLATED FROM KOLA NUTS
D. O. Adeniyi, S. B. Orisajo and K. B. Adejobi
Plant Pathology Section, Crop Protection Division, Cocoa Research Institute of Nigeria, Km 14,
Ibadan-Ijebu-Ode Road, PMB. 5244, Ibadan, Nigeria
Corresponding author: D. O. Adeniyi; E-mail: deleadeniyi7@gmail.com
ABSTRACT: The storage lifespan of kola nuts is challenged by the problem of decay of nuts in
storage as a result of the attack by the rot fungus (Fusarium spp). The effect of the neem leaf
(Azadirachta indica) extracts on the rot fungus was investigated in order to aid extended kola nuts
storage. The aqueous and ethanolic leaf extracts of neem plant in varied concentrations were used
as amendments of 20 ml of potato dextrose agar (PDA) at ambient temperature. It was observed
that the various concentrations (5.0, 10.0, 15.0, 20.0 and 25.0 g/cm3) of the neem leaf extracts
inhibited radial growth of Fusarium spp Significantly with 20.0 and 25.0 g/cm3 having the best
mean percentage inhibition of 82%. The ethanolic extracts had a higher inhibition of Fusarium spp.
at lower concentrations compared to aqueous extracts but both extracts were significantly better
than the control.
Keywords: Kola nuts, Neem, Azadirachta indica, leaf extraction, Fusarium spp, rot fungus
INTRODUCTION
Cola is a tropical African genus that belongs to the family Sterculiaceae, with over a hundred
species. The two most commonly used species and of greatest economic importance are the Cola
acuminata and C. nitida (Lovejoy, 1980). Kola nuts are often stored immediately after harvest in
baskets lined with leaves, however the high rate of transpiration forming droplets of water on their
surface initiate the development of various parasitic fungi (Opeke, 2005).
Cola nitida and C. acuminata were believed to be resistant and biologically robust species and have
no important diseases associated with them (Russell, 1955), but reports have shown that Cola
species are vulnerable to a host of fungal diseases that can attack all parts of the crop
(Oludemokun, 1979). Various publications have shown that, storage of kola nuts in basket with
fresh leaves at a high temperature and high humidity provokes development of various parasitic
fungi, especially wet rots caused by Fusarium and Penicillium species (Oludemokun, 1979). One of
the principal post harvest pathogens was found to be Fusarium sp (Gohil and Vala, 1996; Gour and
Sharmaik, 1998; Pandey et al., 1992; So, 1990; Tariq and Magee, 1990).
Plants have been known for their medicinal and anti-microbial properties since ancient times.
Research attention has recently been focused on alternative safe and cheap methods of managing
pathogenic microorganisms. Some plants extracts harbor inhibitors that alter sporulation and
vegetative growth (Abdel-Raouf, 2001). Some members of the family Meliaceae are known to
pathogenic properties of fungus (Ram et al., 2000).
Azadirachta indica is a well-known medicinal plant. For more than 200 years, it has been used as
one of the most versatile medicinal plant having a wide spectrum of biological activity. Scientists
have derived some beneficial compounds from it for diseases control. Such natural plants products
are biodegradable, exhibit structural diversity and rarely contain halogenated atoms (Hina, and
Arshad, 2007).
A large number of compounds have been isolated from various parts of neem. Those with
antifungal biological activity are nimbidin, gedunin, cyclic trisulphide and cyclic tetrasulphide
(Kausik et al., 2002).
This study was undertaken to evaluate the antifungal potential of aqueous and ethanolic extracts of
the leaves of A. indica against Fusarium spp isolated from kola nuts.
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2. Adeniyi et al.: IJOTAFS 4(1): 2010
MATERIALS AND METHODS
Fresh leaves of neem (Azadirachta indica) were collected and washed thoroughly in water. The
leaves were air-dried on laboratory bench at room temperature and ground into powder using
mortar and pestle. The hot water extraction of the leaves was achieved by infusing 5.0, 10.0, 15.0,
20.0 and 25.0 g of A. indica powder into 100 ml of sterile distilled water in a 250 ml conical flask in
water bath at 50OC for 2 hours. This was allowed to cool and the crude extracts obtained from the
infusion by filtration through sterile muslin cloth to give concentration of 5, 10, 15, 20 and 25%
respectively. The ethanolic extraction of the neem leaf was prepared according to the method of
(Ayoola et al., 2008).
Potato dextrose agar(PDA) was prepared routinely and 10% lactic acid added to suppress bacteria
growth. The Fusarium sp was isolated from the storage rot development in kolanut using the
method of (Hina and Arshad, 2007), with some modifications and maintained on Agar PDA
medium.
The effect of neem leaf extract was tested on the mycelial growth of the isolated fungus. Five ml of
each of the percent concentrations of the neem extract were mixed thoroughly with about 20 ml of
PDA separately in Petri dishes and were allowed to solidify. An inoculum disc of 4 mm diameter of
the pure culture of the isolate was placed on the potato dextrose extract agar in each Petri dish
and replicated thrice. Five ml of sterile water in place of the extracts serve as control. The plates
were incubated at ambient temperature and observations were recorded at regular interval.
The toxicity of the crude and ethanolic extracts was determined against the pathogen. The percent
inhibition of mycelial growth over control was calculated using the formula:
Percentage of inhibition = 1 –
Diameter of treated colony
Diameter of control colony
RESULTS AND DISCUSSION
The aqueous and ethanolic extracts of the leaf of A. indica showed varying degrees of inhibition on
Fusarium sp by suppressing their mycelial growth. The degree of inhibition in both methods of
extraction increased with the increase in the concentration of leaf extract, but the control showed
zero inhibition.
The mycelial growth inhibition by the aqueous leaf extract ranged from 14 – 82% at 20 and 25%
concentration, while that of the ethanolic extract was from 30 – 82% at the same extract
concentrations (Table 1).
Table 1: Inhibition of Aqueous and Ethanolic extracts on mycelial growth of Fusarium spp.
Leaf extracts concentration
Percentage Inhibition
Water extracts (%)
Ethanolic extracts (%)
5
14d
30d
10
25c
41c
15
32b
72b
20
82a
82a
25
82a
82a
0 (Control)
0e
0e
Mean followed by the same letter in the same column are not significantly different (P=0.05)
The ethanolic extract tested was shown to be more effective as it was seen to have greater percent
of inhibition on the fungus compared to the aqueous extract. However, both exhibit equal
inhibitions of the mycelial growth at 20 and 25% extracts concentrations. The ethanolic extracts
again had higher inhibition of Fusarium spp. at lower concentrations compared to aqueous extracts.
Azadirachta indica has been reported as effective against Fusarium oxysporum causing wilt disease
of Solanum melogena. A. indica was effective in reducing the mycelial growth of F. oxysporum at
50% concentration of plant extracts (Siva et al., 2008). The present results are also in agreement
with the earlier report by Govindachariu et al. (1999) that A. indica showed high antifungal activity
against spore germination of F. oxysporum and Colletotrichum lindemuthianum. Extracts of Tridax
procumbens and Capparis deciduas were also reported to totally inhibit spore germination of F.
oxysporum (Bindu and Padma, 2009). The aqueous extracts of A. inidica significantly suppressed
the biomass of Macrophomina phaseolina. There was a gradual decrease in fungal biomass with
the increase in extract concentration (Hina and Arshad, 2007).
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3. Adeniyi et al.: IJOTAFS 4(1): 2010
CONCLUSION
Azadirachta indica as shown in this experiment is effective in inhibiting the mycelial growth of
Fusarium spp in-vitro. Azadirachta indica could thus serve as inhibitor of Fusarium spp. associated
with kola nuts as observed in this experiment.
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