Isolation Of Microorganisms Associated With Deterioration Of Sweet Potato (Ipomoea Batatas (L.) Lam) During Storage

ABSTRACT

Microorganisms associated with the sweet potatoes during storage were analyzed by isolation, characterization and identification. The bacteria belong to Erwinia spp isolated pathogenic fungi includes: Aspergillus Niger, Fusarium oxysporum, Aspergillus flavus, Rhizopus Stolonizer and Botryobiplodia spp respectively. Rhozopius sp has the highest percentage occurance of (27.3%) followed by Aspergilus niger (24.4%) and Aspergilus flavus (12.12%) has the least frequency percentage. Pathogenity test revealed that Rhizopus spp and Botryobiplodia sp is the most virulent and Aspergilus flavus is the least virulent fungus. The only isolated bacteria pathogen Erwinia sp (3.0mm) had rod shape and was gram negative. Spoilage of sweet potatoes during the storage is a major problem for both farmer and consumer. The study concluded that the one strains of spoilage bacteria and one strain of fungal should be taken into serious consideration during any proposed preservation methods of storage of sweet potatoes. 

TABLE OF CONTENTS

Title page ﾿ i

Certification ﾿ ii

Dedication ﾿ iii

Acknowledgements ﾿ iv

Table of contents ﾿ v

List of tables ﾿ vii

List of figures ﾿ viii

Abstract ﾿ iv

CHAPTER 1

1.0 ﾿ INTRODUCTION ﾿ 1

1.1 ﾿ Aims and Objectives ﾿ 4

CHAPTER 2

2.0 ﾿ LITERATURE REVIEW ﾿ 5

2.1 ﾿ The Sweet Potato (Ipomoea batatas) ﾿ 5

2.1.1 ﾿ The Origin ﾿ 6

2.1.2 ﾿ Cultivation ﾿ 7

2.1.3 ﾿ Nutrient Content ﾿ 8

2.2 ﾿ Microbial Spoilage of Potatoes ﾿ 10

2.2.1 ﾿ Rhizopus Sp. ﾿ 10

2.2.2 ﾿ Sclerotinia screrotiorum ﾿ 11  

2.2.3 ﾿ Botrytis Cinerea  ﾿ 12

2.2.4 ﾿ Fusarium oxysporum ﾿ 13

2.2.5 ﾿ Alternaria solani ﾿ 14

2.2.6 ﾿ Ralstonia solanacearum ﾿ 15

2.3 ﾿ Disease and Pests ﾿ 16

2.3.1 ﾿ Fungal Diseases ﾿ 16

2.3.2 ﾿ Nematodes ﾿ 18

2.3.3 ﾿ Insects ﾿ 19

2.4 ﾿ Harvesting, Curing and Storage ﾿ 21

CHAPTER 3

3.0 ﾿ MATERIALS AND METHODS ﾿ 22

3.1 ﾿ Materials ﾿ 22

3.2 ﾿ Source of sweet potatoes ﾿ 22 

3.3        Media Preparation ﾿ 22

3.3.1 ﾿ Incubation of Culture Media ﾿ 22

3.3.2 ﾿ Subcutting/Purification of Fungal Isolates ﾿ 23

3.3.3 ﾿ Incubation of Culture Media ﾿ 23

3.3.4 ﾿ Characterization and Identification of Bacterial Isolates ﾿ 23

3.4 ﾿ Gram Staining Methods ﾿ 23

3.5 ﾿ Biochemical Test ﾿ 24

3.5.1 ﾿ Motility Test ﾿ 24

3.5.2 ﾿ Catalase Test ﾿       24

3.5.3 ﾿ Coagulase Test (Slide test) ﾿       24

3.5.4 ﾿ Oxidase Test ﾿       25

3.5.5 ﾿ Citrate Utilization Test ﾿       25

3.5.6 ﾿ Indole Test ﾿       26

3.5.7 ﾿ Voges-Proskauer Test ﾿       26

3.5.8 ﾿ Methyl Red Test ﾿       27

3.5.9 ﾿ Characterization and identification of fungi isolates using lactophenol ﾿        27

﾿ cotton blue staining

3.5.10 ﾿ Pathogenicity Test (Test for spoilage potential of the bacterial isolates) ﾿             28

3.6 ﾿ Confirmation of Isolates used in Pathogenecity Test ﾿ 28

CHAPTER 4

4.0 ﾿ RESULTS ﾿ 29

CHAPTER 5

5.0 ﾿ DISCUSSION AND CONCLUSION ﾿       34

5.1 ﾿ Discussion ﾿ 34

5.2 ﾿ Conclusion ﾿ ﾿ 35

Reference ﾿ 37