Antifungal Effect of Cymbopogon citratus, Eucalyptus camaldulensis and Azadirachta indica Oil Extracts on Sorghum Seed-Borne Fungi
I. Somda ,
The aim of the study was to evaluate the potential of essential of from local plant in controlling some major seed-borne fungi of sorghum grow in Burkina Faso. Essential oils from Cymbopogon citratus (Lemongrass) Eucalyptus camaldulensis, (Eucalyptus) and crude oil from Azadirachta indica (Neem) were tested in vitro for inhibitory activity against Colletotrichum graminicola, Phoma sorghina and Fusarium moniliforme. Plant extracts were also tested on naturally infected sorghum seeds for controlling the fungi above mentioned. Essential oil from C. citratus significantly inhibited the in vitro radial growth of C. graminicola (76.2% inhibition), compared to the fungicide Dithane M-45. The mycelial growth of P. sorghina and F. moniliforme was slightly affected by this oil at the concentrations used. The extent of inhibition of the fungal growth was dependent on the concentration of essential oil used. Neem crude oil and Eucalyptus essential oil presented low inhibitory activity against test fungi. Concentrations of Eucalyptus essential oil were not harmful to sorghum seedling growth, while neem crude oil was highly phytotoxic. Essential oil of lemongrass at the concentration of 6% was effective in controlling seed-borne infection and seed-to-seedling transmission of C. graminicola and P. sorghina without affecting seedling development. Lemongrass has the potential to be used as sorghum seed treatment for controlling C. graminicola, P. sorghina and F. moniliforme.
Sorghum (Sorghum bicolor (L.) Moench) is widely grown in the Soudano-Sahelian and Sahelian zones of West Africa. It constitutes, together with pearl millet, the staple food of most populations in these areas (Gueye and Delobel, 1999). Based on 1984-1998 averages, the production of sorghum is estimated to 49% of cereals grown in Burkina Faso. Abiotic and biotic stresses limit sorghum production. Leaf anthracnose, grain anthracnose and grain mould are the most important constraints of sorghum production in Burkina Faso. It was reported that the combined effect of leaf and stalk infection by Colletotrichum graminicola (Ces.) Wilson can cause yield losses ranging from 8 to 46%. Mould fungi such as Fusarium moniliforme Sheldon (Syn. F. thapsinum Klittich, Leslie, Nelson et Marasas sp. nov. (Klittich et al., 1997)) and Phoma sorghina (Sacc.) Boerema, Dorebosch and van Kesteren were found at high incidence on seed samples from Burkina Faso tested at the Danish Seed Health Centre (former DGISP) (Somda, unpublished data).
Good quality seed of improved varieties does not reach the traditional small-scale
farmers. They use their own seeds extracted from plants without paying attention
to diseased or healthy plants. Traditionally, smallholder farmers do not apply
chemical seed treatment for the control of sorghum diseases because they cannot
afford it. Widespread public concern for health and environmental effects of
synthetic pesticides and the restriction of their use create an opportunity
for alternative products, in particular reduced-risk pesticides (Isman, 2000;
Alvarez-Castellenos et al., 2001). Research on natural products including
plant extracts which might substitute agrochemicals or contribute to the development
of new agents (Addor, 1995) cited by Alvarez-Castellenos et al. (2001)
for disease control is extremely important. Many authors have shown that certain
essential oils have properties against some important plant pathogens (Montes-Belmont
and Carvajal, 1998; Alvarez-Castellenos et al., 2001; Soliman and Badea,
2002; Daferera et al., 2003; Nguefack et al., 2004; Nguefack et
al., 2005). In developing countries, the use of plant parts or derivatives
such as wood-ash to control insect pests of stored products and backyard vegetables
has been practiced (Owusu, 2001). In Nigeria, lemongrass powder and essential
oil have effectively protected melon seeds against toxigenic Aspergillus
flavus (Banjole and Joda, 2004). Neem seed crude oil and leaf extracts
efficiently controlled rice blast in vitro and in vivo (Amadioha,
2000). Neem crude oil and other plant derivatives have been used by smallholder
farmers to protect their own-saved seed, grain and legumes against insect pests
in Burkina Faso (Sérémé Paco, personal communication).
Although many workers in developing countries reported on antifungal properties
of plant extracts, potential of local plants needs to be documented in Burkina
Faso. Therefore, the aim of this investigation, is to test the effectiveness
of oil extracts of botanicals namely Cymbopogon citratus (D.C.)
Stapf., Eucalyptus camaldulensis Dehnh. and Azadirachta indica
A. Juss. in controlling sorghum seed-borne infection by C. graminicola,
F. moniliforme and P. sorghina and investigate the effects of
extracts on seedling growth and seed-to-seedling transmission.
MATERIALS AND METHODS
Fungal isolates: Isolates of Colletotrichum graminicola, Fusarium moniliforme and Phoma sorghina were recovered, in 2003 at DSHC (former DGISP), Denmark, from sorghum seeds collected in 2002 in Burkina Faso. The isolates were preserved on dry sterile soil and sand mixture in glass tubes for long term storage. A dense suspension (2-5 mL) of mycelium plus spores scraped from agar cultures was added into each vial and mixed with the soil. The screw caps were wrapped with Parafilm® to prevent dehydration. The tubes were stored at 5°C until use.
Sorghum seed samples: Naturally infected sorghum seeds from farmers own saved seed lots were chosen based on the pericarp colour (red and white) and on the incidence of C. graminicola, P. sorghina and F. moniliforme revealed by the standard blotter test performed at DSHC according to Mathur and Kongsdal (2003) (Table 1).
Botanicals and synthetic fungicide: Essential oils and crude oil were used in this study (Table 2). Essential oil (CEO) of lemongrass (Cymbopogon citratus), essential oil (EEO) of Eucalyptus (Eucalyptus camaldulensis) and crude oil (NCO) of neem (Azadirachta indica) were tested. The essential oils were prepared by the Research Institute for Applied Sciences and Technology (IRSAT) of Burkina Faso. Extraction was performed by using stream distillation. Throughout the study, the commercial fungicide Dithane M-45 (Zinc-manganese ethylene bisdithiocarbamate) (Dow chemicals) was used as positive control.
Testing effect of oil extracts on fungal growth: One isolate of each test fungal species was tested in three replicates for each concentration of Essential Oil (EO) using the agar diffusion method. Four concentrations of essential oils (2, 4, 6 and 8%) were tested. The oils were emulsified using 0.1% sterilized water agar (Remmal et al., 1993). Conidial suspensions of 106 conidia mL-1 were prepared from 7 days agar cultures. A drop of 50 μL of the suspension was streak on agar plates (9 cm diameter) containing 25 mL PDA. Ten microliters of the EO emulsion were loaded into each of the four wells (2 mm diameter) made in the agar medium. Control plates were loaded with either water agar (0.1%) or Dithane (0.3%,w/v). The plates were incubated at 25±1°C under cycles of 12 h NUV light/12 h darkness for 2-3 days. The Inhibition Zone (IZ) around each well was evaluated by measuring two perpendicular diameters for each well. The mean of diameters of the four wells gave the IZ for each replicate.
Seed treatment with oil extracts: The seeds were treated with an emulsion
of essential oils (Eos) in 0.1% water agar solution.
||Sorghum seed samples collected in south western region of
Burkina Faso and their natural infection rates by pathogenic fungi
||Plant species collected from Ouagadougou, Burkina Faso environment
and tested in this study
Four concentrations were considered based on preliminary test (data not shown). The EO emulsions were tested at the concentrations 2, 4, 6 and 8%. One hundred microliters of the mixture were applied per gram of seeds in 50 mL-Erlenmeyer flasks according to Adegoke and Odesola (1996). Negative controls were treatment with water agar and untreated seeds. The positive control was treatment with Dithane M-45 at the rate of 0.3% of seed weight. After treatment, the flasks were covered with Parafilm®, shaken for 5 min and maintained overnight at 20-22°C in darkness.
Testing effect of oil extracts on seed health: Two hundred seeds were tested for each treatment. The oil-treated seeds were plated in Petri dishes containing three layers of moistened blotter papers according to Mathur and Kongsdal (2003). A set of four plates (100 seeds) was considered as replicate. Petri plates containing 25 seeds were considered as sub-replicates and randomly arranged in the incubation room. The positive control was treated with Dithane M-45 (0.3%, w/w). The negative control was treated with water agar. Set of untreated seeds was also considered. The disease incidence was recorded as percent of seed bearing a given fungus per replicate.
Testing effect of oil extracts on seedling emergence and growth: Two hundred seeds per treatment (100 seeds per replicate) were used for the growing-on test. Seeds were treated as described for the seed health experiment and were planted in standard peat soil (Weibull K-Soil) in plastic pots (14x13x6 cm), i.e., 25 seeds per pot and eight pots per treatment. After sowing, the pots were incubated in growth chamber at 28±2°C under cycles of 12 h fluorescent light/12 h darkness. Four pots per replicate were randomly arranged in the trays. After 3, 7 and 14 days, seedling emergence was evaluated and percentage of emerging seedlings calculated. After 14 days of incubation, the seedlings from each replicate were cut at the soil level and weighed.
Testing effect of oil extracts on fungal seed to seedling transmission: After weighing, 20 fresh plants randomly picked per replicate (i.e., five plants per pot) were assayed for recovery of the four seed-borne fungi cited above. The first leaves were removed and plated on moistened blotters. After surface disinfection and sterilization in 70% ethanol for 30 sec and in 1% sodium hypochloride for 1 min, respectively, stems were cut aseptically into smaller sections from the base up to ca 10 mm. These segments were plated on three layers of moistened blotter papers in Petri dishes and incubated at 25±1°C under NUV light (12 h/12 cycles). Stem and corresponding first leaf were plated and marked accordingly. After five days, the fragments were inspected under stereomicroscope for the presence or absence of the target fungi.
Data analyses: Treatment effects were determined by one-way analysis of variance using a completely randomised design. The significance of differences between treatments was determined, using the Least Significant Difference (LSD) test of Statgraphic statistical software, version 5. Pearson correlation was also performed to reveal the relationships between different parameters.
Effect of oil extracts on fungal radial growth: Isolates of C. graminicola, P. sorghina and F. moniliforme recovered from naturally infected seeds were tested in vitro. The results of this study showed differences in sensitivity of the different fungal species and in potency of essential oils. C. citratus essential oil exhibited antifungal activity against all the three species of fungi. E. camaldulensis essential oil showed very low level of antifungal activity and neem crude oil had no adverse effect on the growth of the test isolates (Table 3). C. graminicola was highly sensitive to essential oil of C. citratus; 76.2% inhibition was obtained using 8% emulsion. Fifty percent growth inhibition was recorded for P. sorghina at the highest concentration, while F. moniliforme was less sensitive to the lemongrass essential oil (21.4-41.3%). A dose dependent inhibition of C. graminicola mycelial growth was caused by lemongrass essential oil.
Effect of oil extracts on seed health: Statistical analyses showed significant
effects of treatments on C. graminicola recorded on sample 47056
and on P. sorghina and F. moniliforme evaluated on sample 205/214.
C. citratus essential oil was more effective than that of E. camaldulensis
on C. graminicola (Table 4). The highest percent
reduction of C. graminicola (94.4%) was recorded at the concentration
6%, while only 16.7% reduction was obtained with E. camaldulensis oil
at concentration 8%. Essential oil from C. citratus was very effective
against P. sorghina with reduction of infection percent ranging from
71.7-95.1%, while infection by F. moniliforme was reduced to levels
ranging from 20.7-62.1% on sample 205/214. Both P. sorghina and F.
moniliforme were less sensitive to E. camaldulensis essential oil
(13.6 and 44.8% reduction of infection, respectively).
||Effect of oil extracts on mycelial growth inhibition of Colletotrichum
graminicola, Phoma sorghina and Fusarium moniliforme1
|1: Data are mean diameters (mm) of inhibitory zones round
12 wells per concentration, 2: Azadirachta indica crude oil,
essential oils of Cymbopogon citratus and Eucalyptus camaldulensis
tested at different concentrations (v/v, oil/water agar). Mean values in
the same column followed by the same letter are not significantly different.
Data within brackets are the percent inhibition compared to treatment with
||Effect of seed treatment with oil extracts on the incidence
of Colletotrichum graminicola, Phoma sorghina and Fusarium
|1: Data are mean N. of infected seeds per replicate, 2:
Essential oils tested at four different concentrations (v/v), 3:
C.g. = C. graminicola, P. s. = P. sorghina, F. m. = F.
moniliforme; Data within brackets are the percent reduction compared
to negative control (WA); WA: water agar, DIT: Dithane-M45 used at dosage
0.3% (w/w), NT: non-treated, nt : not tested. Mean values followed by the
same letter are not significantly different (p<0.05)
Effect of oil extracts on fungal seed to seedling transmission: Treatment
effects on transmission of the target fungi from seeds to leaves and stems were
not statistically significant. Therefore, Fig. 1 describe
the trend of the seedling infection compared to percent infection of seed. The
transmission rate was higher than expected, based on the results from the seed
health testing. On sample 47056, having the highest initial incidence of C.
graminicola (10.5%), leaf and stem transmissions were observed with percent
infection more than 10% (Fig. 1a). C. citratus essential
oil reduced interestingly the transmission of C. graminicola and P.
sorghina, as compared to the water agar control (Fig. 1a,
b). E. camaldulensis had no adverse effect on the
transmission of the target fungi (Fig. 1). As shown in Fig.
1b, P. sorghina was less transmitted to both leaves and stems, while
F. moniliforme appeared highly transmitted to seedlings of both samples
tested (Fig. 1c, d). The synthetic fungicide
Dithane M-45 also appeared less effective against F. moniliforme on sample
205/214 (Fig. 1d). On sample 205/214 exhibiting 20.25% seed
infection in the original sample, there was no apparent difference in seed-to-seedling
transmission of F. moniliforme after treatments.
Effect of oil extracts on seedling emergence: A highly significant treatment
effect on seedling emergence was found at the different dates of evaluation
(Fig. 2). All the treatments were compared to the water agar
control for both seed samples (47056 and 205/214) displaying potential emergence
of 84 and 82%, respectively. Neem crude oil showed high inhibitory effect on
seed germination and emergence on both samples. Emergence of 40% was hardly
obtained with neem oil across the sample and the dates of evaluation (Fig.
2). Essential oil from C. citratus showed a clear depressive effect
on sample 47056 when high concentrations were used (Fig. 2a).
Lower concentrations (2 and 4%) were as good as the negative control (ca
100% emergence). Emergence was 10% higher with Dithane treatment than that of
the negative control (Fig. 2a). The same trend was observed
with sample 205/214 Fig. 2c). The highest concentration of
C. citratus essential oil (8%) was markedly harmful to emergence. Interestingly,
concentration of 6% was as effective as 2 and 4% in having no depressive effect
on seedling growth. In return, essential oil from E. camaldulensis was
slightly more effective than the control with percent emergence ranging from
100-110% on the white sorghum sample 47056 (Fig. 2b).
||Effect of essential oils on seed infection and seed to seedling
transmission of C. graminicola, on sample 47056 (a), P. sorghina
on sample 205/214 (b) F. moniliforme on samples 47056 and 205/214,
respectively (c, d)
||Effect of treatment with essential oils of Cymbopogon citratus
(Cc) (a, c), Eucalyptus camaldulensis (Ec) (b, d) at four concentrations
and neem crude oil on the emergence percentage of two sorghum samples (47056
and 205/214) compared to water agar control (potential emergence of the
samples 47056 and 205/214 are 84 and 82%, respectively)
Similarly, on the red sorghum sample 205/214, the effects of the different
concentrations used were comparable to the controls. On both samples, concentrations
of E. camaldulensis essential oils had no adverse effect on seedling
emergence which percentages ranged from 95-110% compared to the negative control
(Fig. 2b, d).
||Effect of plant extracts on sorghum seedling growth rate (nb
day-1) and total biomass (g)2
|1: Data are mean numbers of seedlings per replicate; 2:
Data are mean fresh weights of seedlings per replicate; 3: A..
indica crude oil, essential oils of Cymbopogon citratus and Eucalyptus
camaldulensis tested at different concentrations (v/v). Mean values
in the same column followed by the same letter are not significantly different
||Relationships between fungal radial growth inhibition seed
health and seed to seedling transmission of Colletotrichum graminicola
(a), Phoma sorghina (b) and Fusarium moniliforme (c)
after treatment with essential oils
|1: Inhibition zones round the wells containing
the antagonist compound tested. Values are Pearson product moment correlation
coefficients followed by *: p<0.05, significant, **: p<0.01, highly
significant, NS: Non significant
Effect of oil extracts on seedling growth rate and biomass production: Neem oil and both essential oils significantly affected seedling growth rate and total biomass (Table 5). Neem crude oil exhibited the greatest inhibitory effect on growth rate (3.6 and 4.5 seedlings day-1 for samples 47056 and 205/214, respectively and biomass (5.6 and 7.0 g for samples 47056 and 205/214, respectively. C. citratus essential oil at concentration of 8% significantly reduced both growth rate and total biomass, whereas E. camaldulensis essential oil had no depressive effect (Table 5).
Relationships between inhibition of fungal radial growth, seed health and
seed transmission: Since essential oils showed effects on different parameters,
the influence between those parameters was evaluated (Table 6).
The inhibitory effect of essential oil treatments on fungal radial growth was
highly and negatively correlated to the incidence of target fungi on seed; correlation
coefficients ranging from -0.76 to -0.93. The transmission of C. graminicola
from seed to stems was weakly and positively correlated to seed infection (0.59).
No significant correlation was found between seed infection of P. sorghina
and its seed to seedling transmission. There were positive and low relationships
between stem and leaf transmission of C. graminicola and P. sorghina.
Mycelial growth inhibition in vitro and seed to stem transmission of
F. moniliforme were negatively and highly correlated (-0.86), while weak
and positive correlation was found between seed infection and stem transmission
Phoma sorghina and Fusarium moniliforme are responsible of grain
mould on sorghum grown in Burkina Faso. Furthermore, Colletotrichum graminicola
is the most threatening grain, leaf and stalk disease of sorghum in smallholder
farmers fields. These fungi were the main pathogens encountered in many seed
samples from Burkina Faso analysed at the Danish Government Institute of Seed
Pathology for Developing Countries, Denmark (Somda et al., unpublished
data). Extracts from local plants (botanicals) may provide resource-poor farmers
with an option to control seed-borne pathogens of their own saved seeds, using
locally available, environmentally friendly methods. The overall aim sought
in this study was to evaluate the efficacy of essential and crude oils in controlling
major facultative pathogens carried by sorghum seeds without inhibiting seed
germination and seedling growth. The agar diffusion test showed that essential
oil emulsions exhibit an inhibitory property against C. graminicola,
P. sorghina and F. moniliforme. Neem crude oil had no effect on
the target fungi. This contrasts with the results of Amadioha (2000), who found
radial growth reduction of Pyricularia oryzae Cav. by neem oil extracts.
The lack of inhibitory activity may be a result of low concentration or lack
of active constituents, or simply because of the oil extraction method. Nevertheless,
results of the radial growth experiments showed that this modified agar diffusion
method was efficient in screening low volumes of essential oils. C. citratus
essential oil showed the highest antifungal activity against C. graminicola,
P. sorghina and F. moniliforme, as compared to the fungicide Dithane
M-45. E. camaldulensis essential oils were slightly effective at high
concentrations. These results showed that the inhibitory effect of C. citratus
essential oil was concentration dependent. Interestingly, strong relations were
obtained between the inhibition of fungal radial growth by essential oils and
their effects on seed infection along with seedling growth regulation. This
result infers that the agar diffusion test can actually be used as a first step
when evaluating the potency of plant extracts to control seed-borne pathogenic
organisms. Another important point raised by present study is that essential
oils were effective in controlling the test fungi on sorghum seeds. Of the three
plants extracts evaluated, C. citratus essential oil was the most potent.
The concentrations of 6 and 8% caused the greatest reduction of seed infection
at levels comparable to the fungicide Dithane M-45. E. camaldulensis
essential oils were inferior as fongitoxicant on sorghum seeds, confirming its
lack of potency demonstrated in vitro. Studies on the uses of plant
extracts to control grain spoilage and phytopathogenic fungi are well documented
(Dubey et al., 2000; Bajwa et al., 2003; Aladi et al.,
2005; Yulia et al., 2006; Cardenas-Ortega et al., 2007). The fungitoxic
effects of lemongrass essential oil were in agreement with the results obtained
by Banjole and Joda (2004), Nguefack et al. (2004) and Abd-El-Khair and
Wafaa (2007). As seed treatment, lemongrass essential oil at concentrations
6 and 8% was more effective against C. graminicola in reducing seed infection
by 66.7 to 94.4% in the white sample (47056) and by 71.7 to 95.1% in the red
sorghum sample 205/214. More than 50% of the growth of F. moniliforme
was reduced by C. citratus essential oil both in vitro and in
vivo on seed whereas E. camaldulensis essential oil was less efficient
even at high concentrations. The weaker control effect obtained with E. camaldulensis
essential oil against all tested fungi could be attributed to its contents of
known antimicrobial compounds. C. citratus from Burkina Faso contained
citral a and b (Menut et al., 2000), which is absent in E. camaldulensis
essential oils (Maximous, 2004).
The potential use of plant oil extracts for the control of plant diseases requires identification of extracts which inhibit the growth of pathogens at non-phytotoxic concentrations. C. citratus essential oil was efficient in reducing seedling infection of C. graminicola, P. sorghina and, in some instances, F. moniliforme at levels comparable to the fungicide Dithane M-45. Low concentrations (2 and 4%) of C. citratus essential oil improved seedling emergence, while high concentrations maintained seedling emergence at a level equivalent to the potential emergence of the original sorghum seed samples.
The present study concludes that lemongrass essential oil at 6% concentration
can be effectively used to treat sorghum seed against pathogenic fungi, namely
C. graminicola and P. sorghina. These findings prompt further
investigations on the effectiveness of this oil extract under field conditions.
The first author wishes to thank DANIDA and the Danish Seed Health Centre for Developing Countries (DSHC), formerly DGISP, for providing the grant and opportunity for this work. Authors are also grateful to Ms Henriette West for reviewing the manuscript.
1: Abd El-Khair, H. and W.M. Haggag, 2007. Application of some Egyptian medicinal plant extracts against potato late and early blights. Res. J. Agric. Biol. Sci., 3: 166-175.
Direct Link |
2: Addor, R.W., 1995. Insecticides. In: Agrochemical from Natural Products, Godfrey, C.R.A. (Ed.). CRC Press, New York, pp: 1-62.
3: Adegoke, G.O. and B.A. Odesola, 1996. Storage of maize and cowpea and inhibition of microbial agents of biodeterioration using the powder and essential oil of lemon grass (Cymbopogon citratus). Int. Biodeterior. Biodegrad., 37: 81-84.
Direct Link |
4: Aladi, D.A., I.A. Oyero, Jimoh and N.A. Amusa, 2005. Fungitoxic and phytotoxic effect of Vernonia amygdalina (L.), Bryophyllum pinnantus Kurz, Ocimum gratissimum (Closium) L. and Eucalyptus globules (Caliptos) Labill water extracts on cowpea and cowpea seeling pathogens in Ago-Iwoye, South Western Nigeria. World J. Agric. Sci., 1: 70-75.
5: Alvarez-Castellanos, P.P., C.D. Bishop and M.J. Pascual-Villalobos, 2001. Antifungal activity of the essential oil of flowerheads of garland chrysanthemum (Chrysanthemum coronarium) against agricultural pathogens. Phytochemistry, 57: 99-102.
Direct Link |
6: Amadioha, A.C., 2000. Controlling rice blast in vitro and in vivo with extracts of Azadirachta indica. Crop Protect., 19: 287-290.
CrossRef | Direct Link |
7: Bajwa, R., A. Khalid and T.S. Cheema, 2003. Antifungal activity of allelopathic plant extracts III: Growth response of some pathogenic fungi to aqueous extract of Parthenium hysterophorus. Plant Pathol. J., 2: 145-156.
CrossRef | Direct Link |
8: Bankole, S.A. and A.O. Joda, 2004. Effect of lemon grass (Cymbopogon citratus Stapf) powder and essential oil on mould deterioration and aflatoxin contamination of melon seeds (Colocynthis citrullus L.). Afr. J. Biotechnol., 3: 52-59.
9: Cardenas-Ortega, N.C., C. Perez-Gonzalez, M.A. Zavala-Sanchez, A.B. Hernandez-Ramirez and S. Perez-Gutierrez, 2007. Antifungal activity of Siselin in protecting stored maize from Aspergillus flavus. Asian J. Plant Sci., 6: 712-714.
Direct Link |
10: Daferera, D.J., B.N. Ziogas and M.G. Polissiou, 2003. The effectiveness of plant essential oils on the growth of Botrytis cinerea, Fusarium sp. and Clavibacter michiganensis subsp. michiganensis. Crop Prot., 22: 39-44.
CrossRef | Direct Link |
11: Dubey, N.K., T. Pramila and H.B. Singh, 2000. Prospects of some essential oils as antifungal agents. J. Med. Arom. Plant Sci., 22: 350-354.
12: Gueye, M.T. and A. Delobel, 1999. Relative susceptibility of stored pearl millet products and fonio to insect infestation. J. Stored Prod. Res., 35: 277-283.
Direct Link |
13: Isman, M.B., 2000. Plant essential oils for pest and disease management. Crop Protect., 19: 603-608.
CrossRef | Direct Link |
14: Klittich, C.J.R., J.F. Leslie, P.E. Nelson and W.F.O. Marasas, 1997. Fusarium thapsinum (Gibberella thapsina): A new species in section Liseola from sorghum. Mycologia, 89: 643-652.
CrossRef | Direct Link |
15: Mathur, S.B. and O. Kongsdal, 2003. Common Laboratory Seed Health Testing Methods for Detecting Fungi. 1st Edn., International Seed Testing Association, Bassersdorf, Switzerland, ISBN-13: 9783906549354, Pages: 425.
16: Maximous, S.L., 2004. Effect of harvest date and steam distillation time on essential oils of three Eucalyptus species growing in EL-Kassasin region. Bull. Fac. Agric., 55: 71-84.
17: Menut, C., J.M. Bessière, D. Samate, A.K. Djibo, G. Buchbauer and B. Shopper, 2000. Aromatic plants composition, antioxidant and antiradical properties of the essential oils of three Cymbopogon species from Burkina Faso. J. Essent. Oil Res., 12: 207-212.
18: Montes-Belmont, R. and M. Carvajal, 1998. Control of Aspergillus flavus in maize with plant essential oils and their components. J. Food Protect., 61: 616-619.
PubMed | Direct Link |
19: Nguefack, J., V. Leth, P.H. Amvam Zollo and S.B. Mathur, 2004. Evaluation of five essential oils from aromatic plants of Cameroon for controlling food spoilage and mycotoxin producing fungi. Int. J. Food Microbiol., 94: 329-334.
CrossRef | PubMed | Direct Link |
20: Nguefack, J., I. Somda, C.N. Mortensen and P.H. Amvam Zollo, 2005. Evaluation of five essential oils from aromatic plants of Cameroon for controlling seed-borne bacteria of rice (Oryza sativa L.). Seed Sci. Technol., 33: 397-407.
Direct Link |
21: Owusu, E.O., 2001. Effect of some Ghanian plant components on control of two stored-product insect pests of cereals. J. Stored Prod. Res., 37: 85-91.
Direct Link |
22: Remmal, A., T. Bouchikhi, K. Rhayour, M. Ettayebi and A. Tantaoui-Elaraki, 1993. Improved method for the determination of antimicrobial activity of essential oils in agar medium. J. Essent. Oil Res., 5: 179-184.
CrossRef | Direct Link |
23: Soliman, K.M. and R.I. Badeaa, 2002. Effect of oil extracted from some medicinal plants on different mycotoxigenic fungi. Food Chem. Toxicol., 40: 1669-1675.
CrossRef | PubMed | Direct Link |
24: Yulia, E., W.A. Shipton and R.J. Coventry, 2006. Activity of some plant oils and extracts against Colletotrichum gloeosporioides. Plant Pathol. J., 5: 253-257.
CrossRef | Direct Link |