Isolation and characterization of fungi associated with spoiled tomatoes



The study examined the various fugal pathogens associated with tomatoes spoilage as well as their preliminary taxonomic grouping up to genus level. 30 samples of the spoiled tomatoes were collected for the study. Morphological studies reveal the fungi members which include members of the genus aspergillus, cladosporium, fusarium. Species of fusarium were seen to be the most occurring in all samples. Statistical analysis also concurred to the fact that fungi are responsible for spoilage of tomatoes purchased in Afaha Nsit. It implies that fungi are greatly responsible for tomato spoilage. Proper handling, transportation and though washing with clean or chlorinated water will go a long way in reducing the risk of tomatoes spoilage by fungi.


Title Page        –           –           –           –           –           –           –           –          

Certification         –        –        –        –        –        –        –       

Dedication  –        –        –        –        –        –        –        –       

Acknowledgements –           –           –           –           –           –          

Abstract          –           –           –           –           –           –           –           –          

Table of Contents       –           –           –           –           –           –           –          


1.1       Background to the study     –           –           –           –          

1.2       Statement of the Problem    –           –           –           –          

1.3       Objectives of the study       –           –           –           –           –          

1.4       Significance of the study    –           –           –           –          

1.5       Research Questions             –           –           –           –           –          

1.6       Hypotheses   –           –           –           –           –           –           –          

1.7     Scope of the Study    –           –           –           –           –          

1.8       Limitation of the Study       –           –           –           –           –          

1.9       Justification  –           –           –           –           –           –           –

1.10    Definition of Terms –           –           –           –           –           –          


2.1       Brief history of Tomatoes Cultivation      –           –           –          

2.2       Tomato production and postharvest spoilage in Nigeria       –           –           –           –           –         

2.3       Over-view of disease symptoms due to fungi in tomato       –           –           –           –           –       

2.4       Physiological disorders of Tomato           –           –           –          

2.5       Control of postharvest diseases and losses of Tomatoes  –           –           –           –           –           –     2.6       Summary of related Literature       –           –           –           –          


3.1       Samples Collection –           –           –           –           –          

3.2       Materials Sterilization         –           –           –           –           –          

3.3       Samples Processing             –           –           –           –           –          

3.4       Isolation of Fungi     –           –           –           –           –           –          

3.5       Characterization and Identification of the Isolates –     

3.5.1   Slide Culture Technique     –           –           –           –           –          

3.5.2   Microscopic Examination –           –           –           –          

3.5.3   Gram Stain    –           –           –           –           –           –           –          

3.5.4   Chlamydospore Formation Test    –           –           –          

3.5.5   Germ Tube Test        –           –           –           –           –           –          

3.5.6   Sugar Assimilation Test      –           –           –           –           –          

3.5.7   Motility Test             –           –           –           –           –           –          

3.6       Pathogenicity Test of the Isolates –           –           –          

3.7       Organoleptic Test     –           –           –           –           –           –          

3.8       Taxonomic of Tomatoes     –           –           –           –           –          


4.1       Result –           –           –           –           –           –           –           –          

4.2       Discussion     –           –           –           –           —         –           –          


5.1       Summary       –           –           –           –           –           –           –          

5.1       Conclusion    –           –           –           –           –           –           –          

5.2       Recommendations   –           –           –           –           –          

            References    –           –           –           –           –           –           –          



1.1       Background to the study

Tomato (Solanum lycopersicum L.) belongs to the family solanaceae and it is an annual sub-tropical fruit vegetable crop. The crop originated from South America and was introduced to Europe in the 16th Century and later to East Africa by colonial settlers in early 1900 (Wamache, 2005). The Lycopersicon esculentum M. (tomato) is an important vegetable crop across the world, originated in West South America (Kimura and Sinha, 2008). The fruits of tomato are popular throughout the world and are used in all kind of stews, soups and also eaten raw in salads. Ripe tomato fruits have high nutritive values, being a good source of vitamin A, B, C and minerals (Elsayed and Edrees, 2014). Because of the importance of tomato as food, it has been bred to improve productivity, fruit quality, and resistance to biotic and a biotic stresses (Kimura and Sinha, 2008).

Tomato has been widely used not only as food, but also as research material. Tomato is a major vegetable crop that has achieved tremendous popularity over the last century. It is grown in every country of the world-in outdoor fields, greenhouses and net houses (Bihn and Gravani, 2006). Tomato plants can grow up to 10 feet tall, but most species are less than three feet tall on average (Yoltao 1985). Tomato plants are perennial, have a weak stem that often sprawls over the ground and vines over other plants (Sravanthi and Gangadhar, 2015).

Fruit of tomato are diverse in size and shape, ranging from small and round to large and variable shapes (Brewer et al., 2006). The size of tomato varies depending on the plant species. Cherry tomato plants produce small, cherry-sized tomatoes (Yoltao, 1985). Tomato fruits contain high amount of carbohydrates, fats, organic acids, water, minerals, vitamins and pigments. Tomato fruits are used in garnishing various cooked food in Nigerian dishes as well as dishes in many other parts of the world. It is estimated that ripe tomato fruits contain approximately 94 % of water, 4.3 % carbohydrates, 1 % protein, 0.1 % fat, 0.6 % fibre and vitamins.

Antioxidant phytochemicals such as the carotene and lycopene are contained in tomatoes (Wogu and Ofuase, 2014; Sravanthi and Gangadhar, 2015). They are good sources of natural antioxidants which include carotenoids, vitamins, phenolic compounds, flavonoids, dietary glutathione, and endogenous metabolites and have been shown to eliminate free radicals, (Sravanthi and Gangadhar, 2015; Pitchaon et al., 2007).

The crop is grown either on open field or under greenhouse technology. Open field production account for 95 % while greenhouse technology accounts for 5 % of the total tomato production (Seminis, 2007). Nigeria is among the Africa’s leading producer of tomato and is ranked 6th in Africa with a total production of 397,007 tones (Usam, 2012).

Tomato crop does well in warm climate with an altitude range of 0 – 2100 m above sea level. It requires rainfall ranging between 760 mm to 1300 mm and deep fertile loam soil that is well drained, with high content of organic matter and a pH ranging between 5-7 (Rice et al., 1994). Fruits are used in salads or cooked as a vegetable, processed into tomato paste, sauce and puree. The nutritional value of tomato makes it a widely accepted vegetable by consumers.

Fruits are rich in calcium, phosphorus, magnesium, copper, niacin, iron, folate, Vitamin A, B6, Vitamin E, Vitamin B2, Vitamin C, iron and carbohydrates (Wamache, 2005). Furthermore, the fruit has medicinal value as a gentle stimulant for kidneys, and washing off toxins that contaminate the body systems. It improves the status of dietary anti-oxidants (lycopene, ascorbic acid and phenols) in diet (George et al., 2004). Tomato juice is known to be effective for intestinal and liver disorders (Wamache, 2005).

Spoilage refers to any change in the condition of food in which the food becomes less palatable, or even toxic, these changes may be accompanied by alteration in taste, smell, appearance or texture. Numerous microbial defects of agricultural crops are characterized by the types of microorganism responsible for the deterioration, the process of infection in the case at fungal invasion follows the development of fungal penetrating structure (appresorium).

Colonization of fungi is a critical phase in the microbial spoilage of tomatoes. The colonization process involves the ability of the microorganism (fungi) to establish itself without the produce (host). This is initiated when fungi depolymerises certain specific cell wall polymers (such as protopectin, the cementing substance) of the produce. The contamination of tomatoes by fungi could also be as a result of poor handling practices in food supply chain, storage conditions, distribution, marketing practices and transportation. Fungi affecting Tomatoes (Lycopersicum esculentum) includes Fusarium oxyspanium, Fusarium stolonifer, Aspergillus niger and Rhizopus stolonifer. Result on the percentage incidence and rot shows that Rhizopus stolonifer caused the greatest rot on tomato fruit. A lot of breeding works have been carried out on tomato up to the point where we now have tomato hybrids that could withstands adverse environmental condition and resistant to diseases and pests (Chuku, Ogbonna, Onue, 2012).

Naturally, Fruits and vegetables carry epiphytic micro flora. During growth, harvest, transportation and further processing and handling the produce can be further contaminated with non pathogenic and pathogenic organisms from soil, human or animal sources (Beuchart, 1995). Outbreaks of food borne illnesses have been recorded in Europe, Japan, United States, Canada and Turkey (Gosh, 2009). Pathogenic fungi, such as Altternaria, Aspergillus, Fusarium, Mucor sp., Penicillium, Rhizopus, and Trichoderma have been implicated in some crop spoilage (Beuchat, 1995).

Fungi contamination of many agricultural products, including tomatoes starts in the fields (Aran et al., 1987). Both the biological and physical damages during the harvest and transportation phases, coupled with large amount of water and soft endocarp makes tomatoes more susceptible to spoilage by fungi (Asan and Ekmeki, 2002: Onuoral and Orji, 2015). Few studies on fungi associated with tomato spoilage are available in Nigeria (Wogu and Ofuase, 2014; Wokoma, 2008; Eni et al 2010: Bashir et al., 2016). The present study isolates and characterizes fungi species associated with spoiled tomatoes in Nigeria.

1.2       Statement of the Problem 

Tomatoes are an attractive cash crop for small scale farmers and provide potential source of employment to many Nigerians. The tomato fruits have been marketed freshly picked from the field and is the best selling fresh market vegetable crop. Despite the human need of tomato, damage as a result of spoilage caused by micro-organisms has been of serious concern. Microbial decay is one of the main factors that determine losses and compromises the quality of the produce. The extent of the losses especially through microbial decay has not been quantified in most areas and where this has been quantified the results are short lived.

Both the biological and physical damages during the harvest and transportation phases, coupled with large amount of water and soft endocarp makes tomatoes more susceptible to spoilage by fungi. In order to provide literature on this area, few studies on fungi associated with tomato spoilage are available in Nigeria. This then motivated the researcher to investigate into isolation and characterization of fungi associated with spoiled tomatoes.

1.3       Objectives of the study

The general objective of this study is to isolates and characterizes fungi species associated with spoiled tomatoes. Specifically, the study intends to:

  • isolates fungi species associated with spoiled tomatoes in Afaha Nsit; and
  • characterizes fungi species associated with spoiled tomatoes in Afaha Nsit.
  • To isolate the fungi organisms from spoilt tomatoes in Afaha Nsit.
  • To characterize and identify fungi in spoilt tomatoes.
  • To determine the prevalence and pathogenicity of fungal organisms.
  • To create public health awareness about the preponderance of fungal organisms.



1.4       Significance of the study

This study provides important information on the current status on isolation and characterization of fungi species associated with spoiled tomatoes in Nigeria and their management using crude plant extracts. The outputs of this study will be important in reducing tomato post-harvest losses by improving the efficiency of post-harvest handling due to better post-harvest management strategies.

1.5       Research Questions

The following research questions are stated to guide the study:

(i)        What are the fungi species associated with spoiled tomatoes in Afaha Nsit?

(iii)     What are fungi species associated with spoiled tomatoes in Afaha Nsit?

1.6       Hypotheses

Ho: fungi are not responsible in the spoilage of tomatoes.

H1: Fungi are responsible in the spoilage of tomatoes.

1.7     Scope of the Study

Researches have been conducted to ascertain the fact that various microorganisms are responsible for the spoilage of tomatoes. Organisms include Bacteria, for example, Pseudomonas and Xanthomon as species as stated by Watt and Merrill (2000). This present study places emphasis on isolation characterization of fungi species associated with spoiled tomatoes in Nigeria. 

1.8       Limitation of the Study

Despite that this research work was to highlight the microorganism association with spoilage of tomato, it was free with a lot of hindrances which include:

  • Time Constant: The research was constrained by the time limit, it posed a treat to the successful coverage intended in the course of this study. We also have a problem of managing time because we needed time to attend lectures which we have the time to do our practical.
  • Cost Factor: The presence of economic hardship in our country posed to a great extent a problem in proving the whole material, information (and transportation) needed other statistical data procured was also limited by cost factor.
  • Unavailability of research material.

1.9       Justification

Since microorganisms have been identified with the major cause of spoilage in fruits and vegetables due to their high water content, proper isolation and characterization of these organisms in tomatoes will greatly reduce the spoilage of this perishable fruit and as such producers and consumers will be able to protect their vegetables (tomato) and also identify spoiled tomatoes that have been attacked by fungi. Works have been done on the isolation and identification of bacteria and fungi on Tomatoes (Okoli, 1998). Little or no work has been done on the isolation and characterization fungi on spoiled tomatoes in Nigeria. Therefore, the major fungi responsible spoilage of tomatoes will be majorly identified and checked.

1.10    Definition of Terms

Isolation: Is the process or fact of isolating or being isolated and may refer to sociology and psychology

Characterization: Is the representation of persons (or other beings works of art.

Fungi: Fungi are any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds as well as the more familiar mushrooms. 

Tomatoes: Tomato scientifically known as Solanum lycopersicum, is a herbaceous plant usually sprawling on ground in the solanacea family and they are close family to tobacco, chili peppers and egg plant.

About Peter Lawson 2732 Articles
Peter Hezekiah Lawson (Sir Pee). The CEO of A reputable researcher, Web Developer, ICT Instructor and a publisher of many research works in Education.