ABSTRACT

Cocoyam and other related tuber crops are susceptible to infection by various species of fungi, at all stages of growth and also during storage of tubers. Tuber rot is a major factor limiting the post-harvest life of cocoyam. Sixteen (16) spoilt cocoyam samples were purchased from Ahiaeke market, Abia State. Fresh and healthy cocoyam cormels and cormels showing no symptoms of rot were also obtained for pathogenicity testing. The points of advancement of rot were inoculated on a solidified Sabouraud Dextrose Agar (SDA) agar. Four (4) different fungal isolates were obtained from rotten cocoyams. The isolates included Aspergillus niger, Sclerotium rolfsii, Fusarium solcmi, and Penicillium which were implicated in the rots. Sclerotium rolfsii and Fusarium solani had the highest frequency of occurrence 56.3% and 37.5% respectively followed by Aspergillus niger and Penicillium species with 31.2% and 18.7% frequency of occurrence. In the pathogenicity testing, species of Sclerotium rolfsii and Fusarium solani were very pathogenic while, Aspergillus niger and Penicillium was mildly pathogenic, Sclerotia rolfsii caused a rot severity of 69.34% on the sample with Fusarium solani following it closely with a rot severity of 43.56% Aspergillus niger and Penicillium recorded 27.2% and 14.8% rot respectively. The inhibitory zones produced by the Bacillus species were ranged from 12mm to 16mm in diameter. Four isolates showed inhibitory effect on the pathogens. Bacillus megaterium exhibited the highest inhibition of 16mm and 12mm against Sclerotium rolfsii and Aspergillus niger. Bacillus subtilis and Bacillus licheniformis recorded inhibition zone of 13mm and 15mm respectively against Penicillium species and Aspergillus niger. Fusarium solani was however only susceptible to Bacillus subtilis with a clear zone of 12mm. From the results obtained in this study, it was revealed that Bacillus species possess potential inhibitory activity against rot-inducing fungi of cocoyam.

TABLE OF CONTENTS

S/N TITLES PAGES

Declaration       i 

Certification        ii   

Dedication iii

Acknowledgement iv

Table of Contents vi

List of Tables viii

List of Figures ix

Abstract x

CHAPTER ONE

1.0 Introduction 1

1.2 Aims and objectives         7

CHAPTER TWO

2.0 Literature review 8

2.1 The importance of cocoyam world wide 14

2.2 Bacterial as Biological Control Agents 15

2.3 Antifungal Antibiotics of Bacillus Species 19

2.4 Diseases of cocoyam 20

2.5 Root Rot Diseases 21

2.6 Symptoms and infection of cocoyam diseases 22

2.7 Management of Fungal Diseases 23

2.7.1 Biological control of fungal diseases 23

3.0 CHAPTER THREE

3.1 Sample collection 25

3.2 Media Preparation

3.3 Isolation of Bacillus Species 25

3.4 Gram Staining 26

3.5 Biochemical Tests 27

3.5.1 Catalase test 27

3.5.2 Methyl red test 27

3.5.3 Voges-Proskeur Test 27

3.5.4 Indole Test 28

3.5.5 Citrate Utilization Test 28

3.5.6 Hydrogen Sulphide (H2S) Production Test 28

3.5.7 Starch Hydrolysis 29

3.6 Isolation Of Fungal Species From Rotten Yam Tubers 29

3.7 Identification Of Fungal Isolates 30

3.8

Pathogenicity Test       30

3.9 In Vitro Antifungal Testing 31

4.0 Result 32

5.0 Discussion and Conclusion 38

5.1 Conclusion 41

References¬ 42