ABSTRACT

This study evaluated the isolation and characterization of fungi species associated with the spoilage of Pawpaw (Carica papaya) Fruit during storage obtained from National Root Crops Research Institute Umudike, Umuahia Abia State Nigeria and MOUAU farm. A total of Twelve (12) Pawpaw (Carica papaya) fruit samples were selected for the study. The various Pawpaw (Carica papaya) Fruit samples were cultured on Potato Dextrose Agar using a pour plate technique. A total of twenty three (23) fungi were isolated and identified as four (4) different fungi species which included; Aspergillus niger, Penicillium digitatum, Rhizopus stolonifer and Mucor spp. were found in this study to be responsible for Pawpaw (Carica papaya) spoilage. However, there were wide variations in the fungi population, with Aspergillus niger 8(66.7%), and Penicillium digitatum 7(58.3%) being most predominant and occurring fungal isolates, followed by Mucor spp 5(41.7%) and Rhizopus stolonifer 2(25.0%) respectively. All the four organisms isolated were confirmed to be pathogenic on the fruits but in varying degrees. It showed that of all the isolated fungi, Aspergilus niger (32.0mm) was highly pathogenic leading to rapid disintegration of treated fruits in 4-6 days while R. stolonifer (29.0mm) and Penicillium digitatum (24.0mm) were moderately pathogenic, while the least pathogenic was Mucor spp (21.0mm), and caused the least amount of rot on the pawpaw fruits. These fungi are known to be toxigenic or pathogenic to health, therefore their presence in Pawpaw (Carica papaya) must be controlled. This should be achieved through proper washing of the harvested Pawpaw (Carica papaya) fruits, disinfection of transit containers, proper handling of the Pawpaw (Carica papaya) fruits to avoid injuries, adequate hygienic practices by the handlers, provision of good storage facilities and the use of safe food grade fungicides.

TABLE OF CONTENTS

Title Page   i

Certification iii

Dedication iv

Acknowledgement v

Table of Contents vi

List of Tables vii

Abstract ix

CHAPTER ONE

Introduction 1

1.1 Background of Study 1

1.2 Objective of the Study 4

CHAPTER TWO

Literature Review 5

2.1 Brief Description of Pawpaw (Carica Papaya) Fruit 5

2.2 Scenario of Food Spoilage Worldwide (e.g. Pawpaw) 5

2.3 Food Spoilage Microorganisms 8

2.3.1 Yeasts 9

2.3.2 Molds 10

2.3.3 Bacteria 12

2.4 Studies on Fungi Associated With Post Harvest Spoilage of Pawpaw 

(Carica Papaya) Fruit 14

2.5 Isolation of Microorganisms Associated With Deterioration of Tomato 

(Lycopersicon Esculentum) and Pawpaw (Carica Papaya) Fruits 16

2.6 Control of Rot and Spoilage of Agricultural Products 17

2.6.1 Good Agronomic Practices, Field Sanitation and Store Hygiene 17

2.6.2 Thermal and Physical Control 19

2.6.3 Biological Control of Rot Organisms 21

2.6.4 Chemical Control of Rots and their Causal Agents in Postharvest Produce 22

CHAPTER THREE

Materials and Methods 25

3.1 Study Area 25

3.2 Source/Collection of Samples 25

3.3 Materials and Media Used 25

3.3.1 Sterilization of Materials 25

3.4 Processing of Samples 26

3.5 Microbiological Studies 26

3.5.1 Preparation of sample and inoculation of samples 26

3.6 Isolation of Fungi 26

3.7 Subculturing/Purification and Identification of Test Fungi Pathogens 26

3.8 Identification of Fungal Isolates 27

3.8.1 Wet Preparation 27

3.8.2 Colonial Morphology 27

3.9 Pathogenicity Testing 27

CHAPTER FOUR

Results 29

CHAPTER FIVE

Discussion and Conclusion 34

5.1 Discussion 34

5.2 Conclusion 37

References