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© 2021 by the authors; licensee Asian Online Journal Publishing Group 
 

Agriculture and Food Sciences Research 
Vol. 8, No. 1, 1-9, 2021 

ISSN(E) 2411-6653/ ISSN(P) 2518-0193 
DOI: 10.20448/journal.512.2021.81.1.9 

© 2021 by the authors; licensee Asian Online Journal Publishing Group 

    
 

 

 
 
 
Impact of the Aerobic Mesophilic Microorganisms on Black Sigatoka of Bananas 
According to the Cropping Systems in the Region of Kisangani (Case of the old 
secondary forest) 

 
Gabriel Akwakwa Hopla1   

Yang Sun2   
Chunyu Sun3 
Odimba Onautshu4 

 

 
( Corresponding Author) 

 
1College of Life Sciences, Jilin Agricultural University, Changchun, China; Faculty of Sciences, University of 
Kisangani, DRC. 
2,3College of Life Sciences, Jilin Agricultural University, Changchun, China. 

 
4Faculty of Sciences, University of Kisangani, DRC. 

 
Abstract 

The microorganisms play crucial roles in the cycle of matter and damage the organic substances, sources of 
electrons, source of carbon, and source of energy for their biosynthesis. In this work, we studied the impact 
of the aerobic mesophiles microorganisms on the black sigatokaof banana in the old secondary forest. The 
objective was to count and to identify the microbial diversity of the forest ecosystems, as well as to study 
their impact on the development of the black sigatoka of banana. The assessment of the microbial 
populations has been done in an experimental field according to a device in blocks of Fischer by the method 
of successive dilutions of coloration of Gram and by the discharge of ascospores. The results showed that 
the rain season was lower in total microbial biomass (700, 7 colonies) than subdry season (840,3 colonies). 
The Bacillus genera have been more represented more than the Coccusgenera. The impact of black sigatoka 
of banana was raised at the cultivar LibangaLikale (40%) and low at Yangambi 5 Km (14%). The 
distribution of microorganisms in depth in the sub-dry season to the level of surface with vegetation was 
considerable either 3819, 3. 103  UFC( UNIT FORMAT COLONY) by gram of soil between 0 and 5 cm 
against 2754,5.103 UFC by gram of soil between 15 and 20 cm. This suggests that the raised number of 
microorganisms could have positive impact on soil fertility by decreasing the illnesses in this ecosystem. 

 
Keywords: Aerobic mesophilic, Black Sigatoka, Cropping systems, Libanga Likale,Yangambi 5Km, Litete, Gros Michel, 
Mycosphaerellafijiensis Morelet, Bacillus. 

 
Citation | Gabriel Akwakwa Hopla; Yang Sun; Chunyu Sun; 
Odimba Onautshu (2021). Impact of the Aerobic Mesophilic 
Microorganisms on Black Sigatoka of Bananas According to the 
Cropping Systems in the Region of Kisangani (Case of the old 
secondary forest). Agriculture and Food Sciences Research, 8(1): 1-
9. 
History:  
Received: 3 November 2020 
Revised: 5 February 2021 
Accepted: 26 February 2021 
Published: 16 March 2021 
Licensed: This work is licensed under a Creative Commons 

Attribution 3.0 License  
Publisher:  Asian Online Journal Publishing Group 
 

Acknowledgement: All authors contributed to the conception and design of 
the study. 
Funding: This study received no specific financial support. 
Competing Interests: The authors declare that they have no conflict of 
interests. 
Transparency: The authors confirm that the manuscript is an honest, 
accurate, and transparent account of the study was reported; that no vital 
features of the study have been omitted; and that any discrepancies from the 
study as planned have been explained. 
Ethical: This study follows all ethical practices during writing.   

 

 

Contents 
1. Introduction ......................................................................................................................................................................................... 2 
2. Material and Methods ........................................................................................................................................................................ 3 
3. Results and Discussion ...................................................................................................................................................................... 4 
4. Conclusion and Suggestions ............................................................................................................................................................. 6 
References ................................................................................................................................................................................................. 6 
 

 
 
 

 

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Contribution of this paper to the literature 
The objective was to count and to identify the microbial diversity of the forest ecosystems, as well as to 
study their impact on the development of the black sigatoka of banana. 

 
1. Introduction 

The soil is not just the support in which plants take root and can provide the nutrients essential for their 
development, but also is a reservoir of microorganisms. 

 These soil microorganisms are important for plant productivity. They are the most abundant living organisms 
in the soil, and they play an active role in the nutrient and organic matter cycle, soil fertility, plant health and 
production.  Over 90% of plants worldwide develop symbiotic associations with at least one type of mycorrhizae 
[1].  

In the soil, there are beneficial bacteria that maintain very intimate relationships with the plant and strengthen 
its natural defenses against stress of biotic origin. 

 Bacteria are of considerable importance in biogeochemical cycles, such as those of carbon or nitrogen with a 
fundamental role in the fixation of atmospheric nitrogen, a function which has been much studied for several 
decades [2].  

The soil is the outermost layer, marked by living things in the earth's crust.  It is the site of an intense 
exchange of matter and energy between air, water and the global cycles of matter [3].''  

It is considered to be one of the most biospheres and is therefore a major reservoir of microbial diversity.  It is 
made up of insoluble mineral debris produced by the fragmentation and alteration of sedimentary rocks (limestone, 
etc.), organic matter (colloidal humus, etc.), living and dead organic matter, air and water, which allow the 
proliferation of telluric microorganisms [4].  

The physical properties of the soil are determined by the sizes of the particles that compose it.  We can classify 
them by decreasing diameter: sands, silts, clay.  The organic part of the soil includes plant debris, animal remains 
and varying amounts of amorphous organic matter called humus.  The gases contained in the soil are mainly 
oxygen, nitrogen, carbon dioxide (CO2) and mineral substances dissolved or dissociated by hydrolysis (mineral 
ion).  Oxygen is important for the metabolism of plants and their growth.  Its presence is also necessary for the 
development of bacteria, and other organisms. 

In the soil, there are not only microorganisms that swarm.  Animals, plants, and viruses are also found [5].  
This population of the soil undergoes great fluctuations because of the physicochemical factors of the soil in 

particular the structure, the organic matters, the textures, the ionic concentration, the temperature, the humidity, 
the pH, the biotic factors: the types of relations (symbiosis parasitism, predation, and commensalism), the 
phenomenon of inhibition.  To these is added the individual potentiality of each species (reproduction, adaptation, 
feeding). 

Soil is considered today as a vital, non-renewable source, which should therefore be preserved, although the 
horticultural uses non-soil growing media.  Most of the methods developed to ensure soil health apply to 
horticultural substrates and every effort should be made to limit the use of synthetic chemical inputs and depreciate 
natural resources such as silt [4].  

 Microorganisms play crucial roles in the cycle of matter and degrade organic matter, sources of electrons, 
source of carbon, and source of energy for their biosynthesis.  By dying, microorganisms in turn help enrich the soil 
with different carbon compounds [6].  

On the other hand, many of them promote the growth of plants, ensure the degradation of pollutants and 
provide compounds of interest, enzymes, antibiotics or other molecules. 

Microorganisms are found in all types of environment found in nature: They colonize all ecosystems, such as 
soil, freshwater and marine water, air, but also more hostile environments such as the poles, deserts, geysers, the 
ocean floor, etc.  Microorganisms found in extreme environments are called  extremophiles [7]. 

Many microorganisms are associated with plants or animals with which they can maintain relationships of 
symbiosis, commensalism or parasitism.  Some microorganisms can be pathogenic, that is, cause disease in plants or 
animals. 

 Man very early used the properties of microorganisms (bacteria) to feed, to heal.  Today the fields of 
application are very varied.  In the food industry, bacteria , such as Lactobacillus,Lactococcusor Streptococcus, yeasts 
and molds are involved in the production of fermented foods, such as cheese, yogurt, beer [7].  

The ability of heterotrophic bacteria to degrade a wide variety of organic compounds is exploited for the 
treatment of polluted soils in bioremediation strategies or for the treatment of wastewater [8].  Bacteria are also 
used in septic tanks to purify them.  In agriculture, some bacteria can be used in place of pesticides in biological 
control to fight plant parasites [9]. (ex: Bacillus thuringiensis), other bacteria will have a beneficial effect on the 
growth of  plants [10].  

Black Sigatoka or Black Streak Disease, caused by the fungus MycosphaerellafijiensisMorelet, is considered to be 
the most devastating disease in the world banana crop [11].   This disease, which has a wide geographic 
distribution, causes early death of infected leaves and is responsible for more than 50% of the losses in banana 
production [11]. 

The banana tree is a giant and perennial herb 1.5 to 9 m tall.  It consists of a corm (underground part) with 
roots and shoots, a pseudo trunk provided with leaves, and a bunch of fruits Jones [12]; Swennen and Vuylsteke 
[13].  Its reproduction is vegetative and ensured by suckers [14]. Bananas are monocots without an aerial 
vegetative stem [15] classified in the order of 

Zingiberal, the Musaceaefamily and the genus of Musa. 
The genus Musa is characterized by inflorescences with bracts inserted separately from the flowers, and 

includes 5 sections: Australimusa, Callimusa, Rhodochlamys, Eumusa and Ingentimusa Swennen and Vuylsteke [13].   
The Australimusa include a species cultivated for its fibers, M. textilis and the Féhi of the Pacific islands bearing an 
erect inflorescence, fruit to be cooked and a colored sap.  The Callimusa include a few ornamental species such as 
M.coccinea.  The Rhodochlamys also include ornamental species such as M. ornata, M. velutina and M. laterita.  Edible 



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bananas belong to the Eumusasection and are divided into three categories according to consumption: cooking 
bananas, dessert bananas and wine bananas. 

In the Democratic Republic of Congo (DRC), it is currently spread in all the provinces [16]. 
Bananas and plantains play an important economic, cultural and nutritional role worldwide, particularly in 

developing countries in the tropics [17]. They are among the main staple foods in producing countries and 
constitute a considerable source of employment and income through local and international markets [18]. 

In the Kisangani region, no studies have been done on the contribution of microorganisms to banana fungal 
diseases. That is why this study was carried out around the Masako Forest Reserve in order to determine the 
impact of aerobic mesophilic microorganisms associated with black Sigatoka of banana. 

The causative agent of MRN for bananas is M. fijiensisMorelet.  According to Cabi [19], this mushroom is 
classified as follows: 
Phylum: Ascomycota. 
Class: Ascomycetes. 
Subclass: Dothideomycetidae. 
Order: Mycosphaerellales. 
Family: Mycosphaerellaceae. 
Genus: Mycosphaerella. 
 

2. Material and Methods 
2.1. Study Area  

The research was conducted in the Kisangani region, around  Masako Forest Reserve (0 ° 36'N, 25 ° 13'E, 
Eastern Province) [20].  Covers  an area of 2105 ha of which 1/3 is occupied by the northeast primary forest and at 
least 2/3 by the secondary forests in the northwest [21].  While the south part of the reserve is occupied by fallow 
and crops (see figure 1). 

The Masako Forest Reserve is part of the relatively humid Guinean-Congolese rain forests.  It includes six 
types of vegetation, including: ruderal vegetation, crop weed, post crop vegetation, Musangacercropioid vegetation, 
Gilbertiondendrondewevrei forest, and aquatic and semi aquatic vegetation.  The soil of the experimental site is 
sandy-clay, lumpy, fine to medium, brittle, with many roots, dark brown in color [22].  All the eco-climatic data 
the position of the city of Kisangani are near the Equator, and give it an equatorial climate of the Af type in the 
Köppen classification [23]. 
 

2.2. Experimental Set Up 
The experimental plots were established in fallow fields and secondary forest according to the Fisher block 

system [24].With 4 treatments and 5 repetitions per treatment.  The blocks, also called repetitions, were made up 
of a group of plots almost forming a square.  Five blocks or repeats each containing six plants of the same cultivar 
was placed in each plot (see figure 2).  Four locally cultivated varieties (Gros Michel, Libanga Likale, Litete and 
Yangambi  5Km) were used and distributed randomly in the plots of each block. 
 

2.3. Biological Material 
The biological material used in this work consisted of soil samples taken under aseptic conditions, using a 

graduated auger, brand Eijkelkamppo Box 469872 G, in a field of old secondary forest.  The type of soil examined 
in this work was of the silty-sandy type with a fine structure and a very strong anthropic activity. 
 

2.4. Plant Material 
The plant material consisted of 4 cultivars of bananas and plantains, including LibangaLikale (Plantain: Musa 

AAB), LibangaLikale (Plantain: Musa AAB), Gros-Michel (Banana: Musa AAA), and Yangambi Km5 (Banana: 
Musa AAA), the most cultivated by farmers in Kisangani region.  The choice of these cultivars was motivated by 
their presence in the study environment and this is justified by several reasons mentioned by the inhabitants of the 
village (figure 3).   
 

2.5. Sampling of Soil Microbial Populations 
We collected the soil under aseptic conditions using an auger. We weighed 10 g of soil under the same 

conditions, and then fixed the sample in 90 ml of peptone water.  A series of successive dilutions was made, but 
only one dilution for 2 Petri dishes due to 1 ml of inoculum per dish was seeded.  The liquefied nutrient agar cooled 
to 45 ° C was poured into the seeded Petrie dish and after solidification, a second layer was poured.  The incubation 
was carried out at 30 ° C for 72 hours.  The number of CFU (Colony-forming Unit) was obtained using the 
following formula: 

1).21,01.( DnnVml

Colonies
N

+
=



 
Where: N: number of CFU / g (ml) of the initial product. 
 ∑ Colonies: sum of colonies of interpretable boxes. 
 Vml: volume of inoculum = 1 ml. 
 n1: number of boxes considered at D1 selected. 
 n2: number of boxes considered at D2 selected ;  D1: Factor of the selected D1. 
 

2.6. Identification of Aerobic Mesophilic Microorganisms 
The bacteria were identified using at genus level using by the Gram staining method. The bacteria were 

classified into two groups: Gram positive colored purple and Gram negative colored pink.  Gram staining was 
based on the principle that crystal violet stains of all bacteria purple or dark blue.  Lugol played the role of an 
etcher.  Alcohol acetone crossed the wall of some bacteria and discolored them.  However, the wall of other bacteria 



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remained impassable by alcohol and retained the purple or dark blue color which was well reinforced by lugol.  
Finally, saffron colored pink or red any bacteria which wall was discolored and did not act on bacteria colored 
purple or dark blue [25]. 

We took the inoculum and spread it on an object slide to get a smear smearusing a platinum loop.  We then 
dried the smear at laboratory temperature and fixed the preparation by passing the bottom of the slide over the 
flame.  Then we covered the entire smear successively with crystal violet, lugol, alcohol and saffron;  while leaving 
a minute of reaction for each dye, except the alcohol which was left for 30 seconds of reaction.  Before switching 
from one dye to another, the preparation was washed with tap water.  Finally, we dried the preparation at 
laboratory temperature, applied a drop of immersion oil and observed under the microscope at 100x objective. 
 

2.7. Mushroom Isolates 
From the samples of collected leaves, the strains of Mycosphaerella spp.  were isolated by the ascospore 

discharge technique on agar medium (H2O Agar), which were then subcultured on Potato Dextrose Agar medium 
(PDA) [24]. For discharge, the pieces of necrotic leaves were first cut, then soaked in sterile distilled water for 20 
minutes to moisten them.  The leaf pieces were then placed inside lids of Petri dishes which were placed on dishes 
containing 3% agar.  The underside of the leaf was directed upwards, facing the culture medium.  The dishes were 
incubated at 25 ° C overnight.  The following day, the ascospores discharged onto the agar overnight were 
subcultured individually on the PDA medium (39 g / l). 

Transplanting was done by observation with an inverted microscope (Motic AE31), carefully recovering, one 
by one, the discharged ascospores using a needle.  The cultures were incubated at 25 ° C. and the phenotype of the 
strains observed after 45 days to evaluate the correspondence with that of M. fijiensis, M. musicola or M. eumusae.  
The strains obtained were subcultured in Petri dishes and in tubes in order to preserve the established collection. 
 
2.8. Evolution of the Disease 

Data were recorded on only one variable: the incidence of the disease. 
The incidence of the disease (number of plants infected with Mycosphaerella fijiensis expressed as a percentage) 

was assessed every 2 weeks from 2 months after planting. 
 

2.9. Data Analysis 
Statistical analysis was performed using R.2.10.0 software. 

 

3. Results and Discussion 
The results of our investigations are presented in Tables 1 to 4 and illustrated by Figures 4 and 5. The total 

density of the microbial flora according to the depth during the dry season and that of rains is presented in table 2. 
 

Table-1. Number of microbial colonies as a function of soil depth during two seasons. 

Season Depth ( cm) Number of colonies 

Sub-dry 

0-5 1238 
5-10 889 

10-15 628 
15-20 606 

Average 840,3 

Rain 

0-5 504 
5-10 588 

10-15 726 
15-20 788 

Average 700,7 

 
By examining Table 1 relating to the density of bacteria during the dry season and that of rain, it appears that 

the number of bacteria varies according to the seasons as well as the depths.  However, the rainy season is low in 
total microbial biomass with an average of 700.7 number of microbial colonies compared to the dry season which 
showed a high value of the number of colonies is 840.3. Furthermore, the number of microorganisms was higher at 
the surface, 1238 between 0 and 5 cm during the dry season and decreases with depth.   

A contrary situation was observed during the rainy season when this number increases with depth since we 
observed 504 colonies on the surface and 788 in depth.  This could be due to the unfavorable climatic conditions on 
the surface during the rainy season allowing the mesophilic bacteria to penetrate in depth and to grow between 20 
and 45 ° C. Compared to previous work, Alexander [26] found 97,510 bacteria per gram of soil, the bacterial titer, 
while Meddah, et al. [27].  found up to 5,4,107. The distribution of bacteria in depth during the dry season and 
that of rain is illustrated in Figure 4. 

Looking at Figure 4, it appears that a decrease in the number of microorganisms was observed with depth 
during the dry season while an increase in this number was observed during the rainy season.  In addition, the 
distribution of microorganisms in depth in the dry season at the level of the planted surface increased from 
3819.3.103 CFU to 3184.8.103 CFU per gram of soil.  This suggests that the environmental conditions of the 
environment are recognized as playing a determining role in the dynamics of colonization by the microbial 
population. 

In the middle of the forest, the densities are much higher and the highest concentrations are located at the level 
of the first 10 centimeters and decrease slightly at the last centimeter.  This suggests that the high number of 
microorganisms could have an impact on soil fertility and thereby decrease the incidence of diseases in this 
ecosystem.  Furthermore, abiotic factors can also affect the specific composition of microbial communities and their 
biochemical potential.  As a result, we see that there is a drop in microorganisms and we have found that the 
number of colonies in certain boxes, for example in the last 20 centimeters deep, is higher than on the surface.   



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The variations recorded are due to physicochemical factors as well as to crops which could exert certain 
influences on microbial populations in the soil.  Also, abiotic factors can affect the specific composition of microbial 
communities and their biochemical potential. 

 The results of the identification of the bacteria by Gram staining during the dry season are presented in Table 
2. 
 

Table-2. Characterization of Bacteria after Gram staining during the dry season. 

subsèche. 

Strains Form Gram Staining Genus Density 

S1 Bacillus Gram+ Bacillus ++++ 

S2 Coccus Gram+ Staphylococcus ++ 

S3 Bacillus Gram+ Bacillus ++++ 

S4 Coccus Gram+ Staphylococcus ++ 

S5 Bacillus Gram+ Bacillus ++++ 

S6 Bacillus Gram+ Bacillus ++++ 

S7 Bacillus Gram+ Bacillus ++++ 

S8 Bacillus Gram+ Bacillus ++ 

S9 Bacillus Gram+ Bacillus + 
Legend:              S: Strain 
                           +: 25% 
                        ++ : 50% 
                      +++ : 75% 
                    ++++ : 100% 

 
In light of this table, it appears that during the dry season, the bacillus and shell forms were observed with a 

large dominance of the first form which also dominates in density.  With regard to Gram staining, all the strains 
observed are Gram + belonging to the genus Bacillus and Staphylococcus.  The method used being specific to genera, 
it did not allow us to determine the species. 

The results of the identification of bacteria by Gram staining during the rainy season are presented in Table 3. 
 

Table-3. Characterization of Bacteria after Gram staining in the rainy season. 

Strains Form Gram Staining Genus Density 

S1 Bacillus Gram+ Bacillus ++++ 

S2 Bacillus Gram+ Bacillus ++ 
S3 Bacillus Gram+ Bacillus +++ 

S4 Bacillus Gram+ Bacillus + 
S5 Coccus Gram+ Diplococcus +++ 

S6 Coccus Gram+ Streptococcus ++ 

Legend:          S: Strain 
                           +: 25% 
                        ++ : 50% 
                      +++ : 75% 
                    ++++ : 100% 

 
The observation in Table 3 shows that the bacillus form has been more observed (4 strains) than the shell form 

(2 strains) although all the bacteria are Gram +.  As for the genus, the bacillus form has been represented by a 
single genus, Bacillus, while the shell form has been represented by the genera Diplococcus and Streptococcus. 

Figure 5 illustrates the incidence of black Sigatoka in bananas and plantains in the old secondary forest. The   
overall rate for all cultivars was below 50%, and ranged from 14 to 40%.  As in previous studies carried out in a hut 
garden [16]. we find that plantains were more susceptible to this disease and therefore had a high incidence, 40% 
for Libanga Likale and 32% for Litete than  banana trees.  In addition Gros Michel was more sensitive to this 
disease (34%) while Yangambi km 5 (14%) showed tolerance to black Sigatoka. 
 

Table-4. Effect of depth on the density (CFU) of bacteria in the rainy season. 

Depth(cm) Sample D1 D2 CFU (103) 

0-5 
B1 260 217 

4113,6 
B2 271 157 

5-10 
B1 219 133 

2600 
B2 105 112 

10-15 
B1 97 98 

1650 
B2 89 79 

15-20 
B1 72 68 

1295,4 
B2 67 78 

Légend: B1 et B2 : Petridish 1 et 2, Cm : Centimeter, D : Dilution, CFU : ColonyFarmat Unit. 

 
The findings showed that there is a high concentration of the CFU density of bacteria (4113.6) followed by the 

depth in CFU density of the bacteria of 2600 of 5-10, the depth on the density of UFC of 10-15 with 1650 UFC, 
and the depth of 15-20cm with 1295.4UFC of bacteria. Table 4 revealed that the density of bacteria decreased 
according to the depth in the rainy season. The density of bacteria was the highest at 0-5cm and lowest at 15-20cm. 

Table 5 showed that the density of bacteria increased according to the depthin the dry season. 
The bacteria were the highest at 15-20cm (with CFU of 2918.2.103) and lowest at 0-5 CFU of 

(995.5.103).As shown in Tables 4 and 5, the density of bacteria varied differently according to the depth 
between these two seasons. 

This result may be explained due to during the dry season,the bacteria moved to moved deep to look for 
their nutrients. 



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Table-5. Effect of depth on the density (CFU) of bacteria in the dry season. 

Depth (cm) Sample D1 D2 CFU (103) 

0-5 
B1 45 47 

995,5 
B2 69 58 

5-10 
B1 72 69 

1609,1 
B2 120 93 

10-15 
B1 88 105 

2145,5 
B2 99 180 

15-20 
B1 111 210 

2918,2 
B2 103 218 

Légend: B1 et B2 : Petridish 1 et 2, Cm : Centimeter, D : Dilution, CFU : ColonyFarmat Unit 

 
Table-6. Incidence of black Sigatoka in old secondary forest. 

Cultivars LibangaLikale Litete Gros Michel Yangambi Km 5 

Plants N PS PI % N PS PI % N PS PI % N PS PI % 

Bloc 1 6 3 3 50 5 4 1 20 4 2 2 50 5 4 0 0 
Bloc 2 5 3 2 40 4 3 1 25 5 3 2 40 5 5 0 0 
Bloc 3 5 4 1 20 4 3 1 25 5 3 2 40 6 4 2 33 
Bloc 4 4 2 2 50 5 3 2 40 5 4 1 20 5 4 1 20 
Bloc 5 5 3 2 40 4 2 2 50 5 4 1 20 6 5 1 17 

Avarage  40  32  34  14 

Standard 
deviation  12.2  12.5  13.4  14 

Legend: N: Number of Plant, P.S.: Plant Saint, P.I.: Plant infected. 

 
Table 6 indicated that the highest incidence of black Sigatoka in old secondary forest was recorded in cultivar 

Libanga Likale (with average of 40%) and the lowest in Cultivar Yangambi 5Km (with average of 14%). We 
concluded that cultivar Yangambi 5Km was the most resistant to black Sigatoka. 
 

4. Conclusion and Suggestions 
The main objective of this work was to count and identify microbial diversity as well as to study the incidence 

of black Sigatoka in old secondary forest near the Masako forest reserve in Kisangani.  The evaluation of microbial 
populations was carried out in an experimental field using a Fischer block device.  Parameters such as density of 
microbial population, depth of soil, characterization of microorganisms and incidence of black Sigatoka were 
assessed during the dry and rainy seasons. 

The results obtained during this work show that: 
The rainy season is low in total microbial biomass (700.7 colonies) than the season dries up (840.3 colonies). 
The bacteria rate increases with depth during the rainy season and decreases during the rainy season. 
The distribution of bacteria in depth in the dry season at the level of the planted area is considerable, at 3,819.3.  

103 CFU per gram of soil between 0 and 5 cm compared to 2754.5.103 CFU per gram of soil between 15 and 20 
cm. 

The number of CFUs during the rainy season varied from 2,990.9.103 to 3,581.8.  103 CFU per gram of soil 
between 0-5 cm and 15-20 cm respectively.  

The incidence of black Sigatoka in bananas is high in the cultivar Libanga Likale (40%) and low in Yangambi 
Km 5 (14%).  In addition Litete and Gros Michel were presented with intermediate values respectively 32 and 34%. 

The number of bacteria is relatively high in this ecosystem and would reduce the incidence of black Sigatoka in 
bananas and plantains 

Statistically, the one-factor analysis of variance has shown that there are significant differences between the 
parameters studied. 
We suggest that: 

In-depth studies are carried out to characterize microorganisms at the level of species existing in the soil in 
order to determine their relationships with soil fertility. 

That other studies be carried out in more depth on the molecular characteristic of microbial communities in the 
Kisangani region in order to better understand them given their very small size. 
 

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Figure-1. Location of the Masako Forest Reserve. 

Source: Adaptation of 2010 satellite photo, of Lisingi and CFT. 

 
 

http://www.cabicompendium.org,/


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Figure-2. Fisher block device. 

 
Legend:  

 : Gros Michel 

 : Libanga Likale 

 : Litete 

 : Yangambi Km 5 

 : Edge plants 

 

 
Figure-3. Banana and plantain cultivars used 

 



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Figure-4. Distribution of bacteria by depth over two seasons. 

 

 
Figure-5. Incidence of black Sigatoka in bananas and plantains in old secondary forest in Masako in 2014. 

 

Statistiques analysis result 
• ANOVA :CFU-Saison 
Df   Sum Sq Mean Sq F value Pr(>F) 
Saison       1   990722  990722  1.0264 0.3282 
Residuals   14 13513548  965253 
meansd n 
Rainy 1917.075  755.6602 8 
Dry 2414.750 1165.9694 8 
 

• ANOVA : CFU-Depth 
Df   Sum Sq Mean Sq F value Pr(>F) 
Depth   3   920840  306947  0.2712  0.845 
Residuals   12 13583431 1131953                
meansd n 
0-5 cm   2554.55 1800.2359 4 
10-15 cm 1897.75  286.0771 4 
15-20 cm 2106.80  936.9240 4 
5-10 cm  2104.55  572.0964 4 
 

• ANOVA : Incidence-Cultivar 
Df Sum Sq Mean Sq F value  Pr(>F)   
Cllivars     3 1880.0  626.67  3.6343 0.03581 * 
Residuals   16 2758.9  172.43 
--- 
Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1  
meansdn 
Gros Michel      34 13.41641 5 
LibangaLikale   40 12.24745 5 
Litete           32 12.54990 5 
Yangambi 5Km     14 14.22049 5 

  

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