MICROBIOLOGICAL CONTROL OF POST-HARVEST FUNGAL PATHOGENS OF COCOYAM USING BACILLUS SPECIES

ABSTRACT

Microbial control of post harvest fungal pathogen of cocoyam using Bacillus species was investigated. Fungi were isolated from rot infested cocoyam corms and identified with varying occurrences levels including Aspergillus (100%), Penicillum (80%), Rhizopus (60%), yeast (100% and Fusarium oxysporium (60%). Pathogencity test implicated three fungi specie as pathogens with  varying levels of demonstrated pathogencity as show by percentage rots of Aspergillus (59%) Fusarium (48.15%) and Penicillum (45%) the inoculate of in-vitro antifungal tests reveals varying levels of antifungal activity with inhibition zones of Bacillus thuruingensis 14.3mm, Bacillus subtilis 13.3mm, Bacillus megaterium 11.0mm and Bacillus cereus 12.7mm. In vitro test recorded percentage inhibitions of 57%. The higher activity was recorded against Fusarium (57%) by Bacillus thuruingensis while the test inhibition was recorded against Aspergillus (41%) by Bacillus megaterium. The different Bacillus species exhibited varying levels of inhibition activity against the cocoyam fungi pathogen. Comparatively Fusarium was the most inhibited with a mean inhibition of 53% while Penicillum was the least inhibited (49%) of all the fungi pathogens. It was observed that the Bacillus growth has potentials for the use as bio-control agent, to protect cocoyam corms after harvest. But there is need for a further study regarding their mode of application in concentrate terms.

TABLE OF CONTENTS

S/N                            Titles                                                                     Page

Title Page                                                                                                                      i

Certification                                                                                                               iii

Dedication                                                                                                                  iv

Acknowledgement                                                                                                      v

Table of Contents                                                                                                       vi

List of Tables                                                                                                              vii

Abstract                                                                                                                      ix

CHAPTER ONE

1.1       Introduction                                                                                                                1

1.2       Aim of the Study                                                                                                        2

1.3       Objectives of Study                                                                                                    2

CHAPTER TWO

2.1       Literature Review                                                                                                       3

2.1       Brief Description of Cocoyam                                                                                   3

2.2       Nutritional Benefits of Cocoyam                                                                               3

2.3       Health Benefits                                                                                                           4

2.3.1    Cancer Prevention                                                                                                      4

2.3.2    Reduce Symptoms of Rheumatoid Arthritis                                                              4

2.3.3    Blood Pressure and Heart Health                                                                               5

2.3.4    Immune System Health                                                                                              5

2.3.5    Cramps                                                                                                                        5

2.4       Scenario of Food Spoilage Worldwide (e.g. Cocoyam)                                            6

2.5       Food Spoilage Microorganisms                                                                                 9

2.5.1    Yeasts                                                                                                                         9

2.5.2    Molds                                                                                                                          10

2.5.3    Bacteria                                                                                                                      12

2.6       Isolation, Identification and Pathogenicity of Fungi Associated with

            Cocoyam (Colocasia esculenta) Spoilage                                                                  14

2.7       Fungi Associated with the Spoilage of Post-Harvest Cocoyam

            (Colocasia esculenta) Sold in Major Markets in Awka, Nigeria                             15

2.8       Control of Rot and Spoilage of Agricultural Products                                               17

2.8.1    Good Agronomic Practices, Field Sanitation and Store Hygiene                            17

2.8.2    Thermal and Physical Control                                                                                    19

2.8.3    Biological Control of Rot Organisms                                                                         20

2.8.4    Chemical Control of Rots and their Causal Agents in Postharvest Produce                       21

2.9       Antibiotics Activities of Bacillus subtilis                                                                   23

CHAPTER THREE

3.1       Materials                                                                                                                     25

3.1.1    Source/Collection of Samples                                                                                    25

3.1.2    Materials and Media Used                                                                                          25

3.1.3    Sterilization of Materials                                                                                            25

3.2       Method                                                                                                                        26

3.2.1    Isolation of Bacillus from Agricultural Soil                                                               26

3.3       Isolation of Fungi from Spoilt Cocoyam                                                                    26

3.3.1    Processing of Samples                                                                                                26

3.3.2    Preparation of sample and inoculation of samples                                                    26

3.3.3    Isolation of Fungi                                                                                                       26

3.3.4    Subculturing/Purification and Identification of Test Fungi Pathogens                    27

3.4       Identification of Fungi Isolates                                                                                  27

3.4.1    Wet Preparation                                                                                                          27

3.4.2    Colonial Morphology                                                                                                 27

3.5       Pathogenecity Test for Fungi Isolate Cocoyam Pathogens                                        27

3.6       In-Vitro Antifungal Activity of Bacillus Isolates against Cocoyam Pathogens        28

CHAPTER FOUR

4.1       Results                                                                                                                        30

CHAPTER FIVE

5.1       Discussion, Conclusion and Recommendation                                                          36

5.1       Discussion                                                                                                                   36

5.2       Conclusion                                                                                                                  37

5.3       Recommendation                                                                                                       37

            References

LIST OF TABLES

Tables             Fungal Isolate

CHAPTER ONE

1.0       INTRODUCTION

Cocoyam (Colocasia esculenta and Xanthsoma sagittofolium) are herbaceous perennial plants belonging to the family aracae and are grown primarily for the edible roots. They are among the tuberous root well adapted to most Agro-ecological zones in Nigeria. Cocoyam (Colocasia esculenta) is widely cultivated and used for food in Nigeria and Ghana and other countries including China and Ghana leading in world production (Onwueme and Charles 2002).

In Nigeria colocasia esculenta specie are the most important food and the third world most important root or tuber crop after the yam and cassava (Onueme, 2008). The production of cocoyam has increased from 643000-1.7million during the past decades; its contribution of root crop has increased from 39-6.8% (Agboola, 2009). In Nigeria, colocasia specie has contributed to the National food security and cash income, producing nations cocoyam are also being considered as a source of starch for use in biodegradable film material for other industrial and pharmaceutical purpose because of interesting properties of the Amylopectin fraction of starch, which is the principal form of cocoyam starch (Cecil, 2001),it has critically contributed to the national food security and cash income producing nations, it is used in brewing industrial or company and the use of cocoyam as composite with other cereals for snack production.

The cormels, corms and leaves are very important source of carbohydrate for human consumption and Animal feed and a good source of income for farmers in Asia, Africa and latin America.

Cocoyam contains digestible starch, good quality protein, vitamin, thiamine, riboflavin, niacin, and high source of essential amino acid. cocoyam excelled in some nutrients and minerals such as iron, calcium, and sodium, thus cocoyam consumption is to be encouraged and popularized as additional tuber crop, inspite of all health benefit cocoyam are neglected and they face a major problem of high susceptibility to physical damage during harvesting leading to high physical damage during harvesting colony to high postharvest losses cocoyam have very short post harvest shelf life.

1.2       AIM OF THE STUDY

The aim of study is to control post harvest fungi pathogens of cocoyam using Bacillus species       

1.3       OBJECTIVES OF STUDY

1.     To isolate and identify fungi associated with post harvest spoilage of cocoyam.

2.     To determine through pathogencity tools, the fungi isolate that are pathogenic to healthy cocoyam.

3.     To isolate and identity some Bacillus species from Agricultural soil  

4.     Determine the Antifungal activity of the Bacillus isolate on the cocoyam fungal pathogens.

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