isolation and characterization of fungi associated with spoiled tomatoes in gwagwalada

Isolation and characterization of fungi associated with spoiled tomatoes in gwagwalada

ABSTRACT

 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 from gwagwalada. 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 gwagwalada. 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. 

 

isolation and characterization of fungi associated with spoiled tomatoes in gwagwalada
isolation and characterization of fungi associated with spoiled tomatoes in gwagwalada

TABLE OF CONTENTS

Title Page     –        –        –        –        –        –        –        –        i

Certification        –       –       –       –       –       –       –       ii

Dedication –       –       –       –       –       –       –       –       iii

Acknowledgements         –        –        –        –        –        –        iv

Abstract       –        –        –        –        –        –        –        –        v

Table of Contents    –        –        –        –        –        –        –        vi

CHAPTER ONE     –        INTRODUCTION

1.1     Background to the study           –        –        –        –        1

1.2     Statement of the Problem         –        –        –        –        6

1.3     Objectives of the study   –        –        –        –        –        7

1.4     Significance of the study           –        –        –        –        7

1.5     Research Questions        –        –        –        –        –        8

1.6     Hypotheses –        –        –        –        –        –        –        8

1.7     Scope of the Study          –        –        –        –        –        8

1.8     Limitation of the Study    –        –        –        –        –        8

1.9     Justification –        –        –        –        –        –        –        8

1.10   Definition of Terms          –        –        –        –        –        –        10

 

 

CHAPTER TWO – REVIEW OF RELATED LITERATURE

2.1     Brief history of Tomatoes Cultivation   –        –        –        11

2.2     Tomato production and postharvest spoilage

in gwagwalada     –        –        –        –        –        –        –        13

 

2.3     Over-view of disease symptoms due to fungi

in tomato     –        –        –        –        –        –        –        19

 

2.4     Physiological disorders of Tomato        –        –        –        22

 

2.5     Control of postharvest diseases and losses

of Tomatoes –        –        –        –        –        –        –        22

2.6     Summary of related Literature   –        –        –        –        29

CHAPTER THREE – RESEARCH METHODS

3.1     Samples Collection          –        –        –        –        –        31

3.2     Materials Sterilization      –        –        –        –        –        31

3.3     Samples Processing         –        –        –        –        –        31

3.4     Isolation of Fungi   –        –        –        –        –        –        32

3.5     Characterization and Identification of the Isolates –          32

3.5.1  Slide Culture Technique –        –        –        –        –        33

3.5.2  Microscopic Examination –        –        –        –        33

3.5.3 Gram Stain –        –        –        –        –        –        –        33

3.5.4 Chlamydospore Formation Test           –        –        –        33

3.5.5  Germ Tube Test     –        –        –        –        –        –        34

3.5.6 Sugar Assimilation Test   –        –        –        –        –        34

3.5.7  Motility Test          –        –        –        –        –        –        35

3.6     Pathogenicity Test of the Isolates       –        –        –        35

3.7     Organoleptic Test  –        –        –        –        –        –        36

3.8     Taxonomic of Tomatoes   –        –        –        –        –        36

CHAPTER FOUR – RESULT AND DISCUSSION OF FINDINGS

4.1     Result          –        –        –        –        –        –        –        –        37

4.2     Discussion   –        –        –        –        —       –        –        38

CHAPTER FIVE – SUMMARY, CONCLUSION AND RECOMMENDATIONS

5.1     Summary     –        –        –        –        –        –        –        40

5.1     Conclusion   –        –        –        –        –        –        –        40

5.2     Recommendations           –        –        –        –        –        41

          References  –        –        –        –        –        –        –        43

 

 

 

 

CHAPTER ONE

INTRODUCTION

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.

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