ISOLATION AND IDENTIFICATION OF FUNGAL PATHOGENS OF TOMATO FRUITS

ABSTRACT

Tomato fruit showing rotten signs were examined for the presence of fungal pathogens inducing spoilage. The isolation of fungi from tomato fruit was carried out on Sabouraud Dextrose Agar (SDA). A total of five (5) fungi isolates were obtained. The fungi found were Aspergillus flavus, A. niger, Fusarium solani, Rhizopus stolonifer and Alternaria alternata. Pathogenicity test carried out revealed that all the fungi isolated were pathogenic. The fungi associated with the spoilage of the tomato fruits were identified based on their colonial and morphological characteristics. These fungi species were found in varying degrees. Aspergillus species (A. niger and A. flavus) had the highest rate of occurrence (47.9%) among the isolated fungi. This was followed by Rhizopus stolonifer and Fusarium solani while Alternaria alternata were the least encountered. It showed that each infected tomato fruit gave the initial organism that caused the spoilage of the fruit. The rot symptoms obtained were similar to those observed previously on the fruits when subjected to identification procedures. The tomato fruits changed colour slightly after infection and became soft thus could easily be punctured with a finger at the point of inoculation. Of all the isolated fungi, Aspergillus niger was highly pathogenic leading to rapid disintegration of treated fruits in 3-5 days while R. stolonifer and Fusarium solani were moderately pathogenic, and Alternaria alternata and Aspergillus flavus was least pathogenic, and caused the least amount of rot on fruits. This study detected the profile of rotten fungi which caused pathogenecity of some tomato fruits in Umuahia North. It showed that fruits decay is caused by mostly fungi and inorder to mitigate this spoilage which can result to economic loss, safe means of preservation should be adopted.

TABLE OF CONTENTS

Title……………………………………………………………………………….……………..i

Certification………………………………………………………………….………………….ii

Dedication………………………………………………………………………………………iii

Acknowledgement………………………………………………………………………………iv

Table of contents………………………………………………………………………………..v

List of tables…………………………………………………………………………………….viii

List of plates…………………………………………………………………………………….ix

Abstract………………………………………………………………….……………………....x

CHAPTER ONE……………………………………………………………………………….1

Introduction……………………………………………………………………………………  1

1.1 Backround information of the study………………….……………………………………..1

1.2  Origin and cultivation………………………………………………………………………4

1.3 Problem statement and justification…………………………………………………………4

1.4  Objectives………………………………………………………...………………………...5

1.5  Significance of study…………………………………………..……….…………………..5

1.6 Objective of study……………………………………………………………………...……5

CHAPTER TWO………………………………………..…………………………………....6

Literature Review………………………………..……………………………………………..6

2.1  Tomato fruit………………………………..………………………………………………6

2.2  Origin and distribution of tomato fruit………………………….…………………….12

2.3 varieties of some tomato fruits…………………………………….…………………..13

2.4  Diseases and pest of tomato …………………………………….…………………….14

2.5  Medicinal properties of Tomato………………………………….…………………...18

2.6  Health Benefit of Tomato fruit…................................................................................19

2.7  spoilage or rot of Tomato fruit………………………………….…………………….20

2.8  Prevention of Tomato rot or spoilage………………………….…………………..…21

CHAPTER THREE……………………………………………….……………………..22

Materials and methods……………………………………………….………………..….22

3.1  Study Area/Experimental site………………………………………………………..22

3.2  Source of Tomato fruits……………………………………………………………...22

3.3  Collection of infected fruits samples………………………………………………...22

3.4  Preparation and sterilization of culture medium……………………………………..23

3.5  Isoltion of fungi from rotten Tomato fruits…………………………………………..23

3.6  Identificaion of pathogen……………………………………………………….…….23

3.7  Test of pathogenecity of the isolated fungi…………………………………………..24

CHAPTER FOUR……………………………..……………………………………...…25

RESULTS…………………………………………..………………………………..…..25

CHAPTER FIVE……………………………..………………………………………..33

DISCUSSION, CONCLUSION AND RECOMMENDATIO………………………33

5.1  Discussion………………………………………………………………………….33

5.2  Conclusion………………………………………………………………………….37

5.3  Recommendation…………………………………………………………………..38

REFERENCES                                                                         

APPENDICES

LIST OF TABLES

Table 1   Fungi isolated from the rotten tomato from Ubani main  market, Umuahia North LGA ……………………………………………………………………….…26

Table 2   Fungi isolated from the rotten tomato from Ahiaeke  market, Umuahia North LGA …………………………………………………………………..………27

Table 3   Fungi isolated from the rotten tomato from Amawom  market, Ikwuano LGA…..…28                                                                    

Table 4   Fungi isolated from the rotten tomato from Ndoro  market, Ikwuano LGA……...... 29

Table 5  Overall prevalence of fungi isolated from the two Local Government of Abia State(Umuahia North and Ikwuano)………………………….30

 Table 6   Pathogenicity test of isolated fungal on fresh tomato fruits......................................31

Table 7   Colonial, Morphological and Celullar Characteristics of Fung in rotten tomato Fruits ……………….………………..32

LIST OF PLATES                                                       

Plate 1     Infected tomato fruits collected from markets in Umuahia………………………….49

Plate 2     Healthy Tomato fruits…………………………………………….……………….…49

Plate 3     Culture of infected Tomato tissue on SDA plate…………….………………….......50

Plate 2      Pathogenecity test on healthy tomato fruit………………………………….............50

CHAPTER ONE

INTRODUCTION

1.1       Background information of the study

Tomato known as  Lycopersicon esculentum  in botanical term belongs to kingdom plantae Angiosperm, order Solanales, family Solanaceae, genus Solanum, and specie Solanum lycopersicum is one of the most important vegetable crops and an important condiment in most diets. Tomato is very rich source of vitamins A and C and it contain high levels of sugars and nutrients elements and their low ph values makes them particularly desirable to fungal decay.   The deep red coloration of ripened tomato fruit is due to the presence of lycopene, a form of beta carotenoid pigment which forms the precursor of vitamin A and hence of great nutritional value. Tomato water content is about 95%, this placed tomatoes as one of the best food in weight reduction.  Although a large amount of this vegetable is produced annually, its availability all year round is limited due to the attending high incidence of pest and diseases as well as poor storage facilities. Microorganisms penetrate the fruits through wounds from handlers, farm equipment, wash water and soil and air borne aerosols. Decay caused by pathogens has been reported to constitute up to about 60% of losses in fresh tomatoes produced.

Fresh tomato fruits are highly perishable with a short shelf-life and high susceptibility to fungal diseases. They are difficult to store for long periods without incurring losses and as the fruits ripen, they become more susceptible to microbial infections (Mujib ur Rehman et al., 2007).

Prolonged shelf life of tomato fruits is essentially achieved by careful harvesting and handling of fruits, optimization of storage environmental conditions and the use of chemicals which are available for the control of pathogens that affect stored products.     

Tomato 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). In Nigeria, tomato plays a vital role in meeting domestic and nutritional food requirements, generation of income, foreign exchange earnings and creation of employment (Sigei et al., 2014). The crop is grown for both fresh domestic and export market but there is increasing demand for processed tomato products (Mungai et al., 2000).  

 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).

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., 1993).  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).  

Tomato production is constrained by factors such as poor pre-harvest practices, adoption of poor production techniques, rough handling and moisture condensation causing pathogen infestation (Kader, 1992). Packaging in bulk without sorting and grading of produce, damage during transport and storage due to mechanical injuries are other factors contributing to post-harvest losses (Kader, 1992).   Inadequate storage, distance and time consuming market distribution, poor access to the market, post-harvest spoilage micro-organisms and cultivars disposition to diseases causes high post-harvest losses of tomatoes (Kader, 1992).  

It has been estimated that 20-50 % of tomato fruits harvested for human consumption are lost through microbial spoilage while other losses result from damage by dynamic stresses during transit, and through rough handling during loading and unloading (Kader, 1992; Okezie, 1998). Thirupathi et al., (2006) estimated the magnitude of post-harvest losses in fresh fruits to be 25-80 %. Post-harvest decay remains a major challenge in tomato production. The magnitude of post-harvest losses vary from one country to another, one season to another and even one day to another (Mujib et al., 2007). There are numerous micro-organisms that cause post-harvest decay of tomatoes. Among these, fungi and bacteria are the most destructive.   

Most of the tomato fruits are also damaged after harvesting because of inadequate handling and preservation methods (Wills et al., 1981). Fruits, due to their low pH, high moisture content and nutrient composition are very susceptible to attack by pathogenic fungi, which in addition to causing rots, may also make them unfit for consumption by producing mycotoxins (Moss, 2002). Mycotoxins are potential health hazards to man and animals and in most cases they are unnoticed. Control of fruit rot also remains a major challenge in tomato production. 

This study was therefore carried out to isolate and identify fungi pathogen associated with deterioration of tomato fruits, and to test the pathogenicity of the identified fungi.

1.2       Origin and cultivation

 Tomato 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). In Nigeria, tomato plays a vital role in meeting domestic and nutritional food requirements, generation of income, foreign exchange earnings and creation of employment (Sigei et al., 2014). The crop is grown for both fresh domestic and export market but there is increasing demand for processed tomato products (Mungai et al., 2000).  

 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). 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). 

1.3       Problem statement and justification

Tomatoes are an attractive cash crop for small scale farmers and provide potential source of employment to many rural and urban. 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 post-harvest spoilage 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. Periodic surveys may help in understanding the severity of losses in a specific place and at a specific time.  Estimates of post-harvest losses in  have Umuahia North local Government area of Abia State have not been established. Therefore the study aims at  identify and isolating  fungal pathogens involved in decay of tomato fruits. 

 1.4     Significance of the study

This study provides important information on the current status, causes of post-harvest losses of tomatoes in Umuahia  Abia State. 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       Aim

This research aimed at isolating and identifying fungi pathogens of tomato fruits and highlights the consequences which might result to the intake of rotten tomatoes.   

1.6       Objectives

 General objective

·       To  isolate fungi from  tomato fruits in Umuahia Abia State.

·       To identify the isolated fungi.

·       To determine the status of the isolated fungi as phytopathogens losses in Umuahia Abia State

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