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Aflatoxin-Producing Fungi and Contamination in Zambia

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Aflatoxin-Producing Fungi and Contamination in Zambia Item Type text; Electronic Dissertation Authors Kachapulula, Paul W. Publisher The University of Arizona. Rights Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author. Download date 10/10/2021 19:50:47 Link to Item http://hdl.handle.net/10150/625642 1" " " " AFLATOXIN-PRODUCING FUNGI AND CONTAMINATION IN ZAMBIA " by " Paul W. Kachapulula __________________________" Copyright © Paul W. Kachapulula 2017 A Dissertation Submitted to the Faculty of the " SCHOOL OF PLANT SCIENCES " In Partial Fulfillment of the Requirements " For the Degree of " DOCTOR OF PHILOSOPHY " WITH A MAJOR IN PLANT PATHOLOGY In the Graduate College " " THE UNIVERSITY OF"ARIZONA" 2017 " " " 2" " THE UNIVERSITY OF ARIZONA GRADUATE COLLEGE As members of the Dissertation Committee, we certify that we have read the dissertation prepared by Paul W. Kachapulula, titled “Aflatoxin-producing fungi and contamination in Zambia” and recommend that it be accepted as fulfilling the dissertation requirement for the Degree of Doctor of Philosophy. " " _______________________________________________________________________" Date: 3 August 2017" Peter J. Cotty " _______________________________________________________________________" Date: 3 August 2017" Barry M. Pryor """" _______________________________________________________________________" Date: 3 August 2017" Marc J. Orbach " _______________________________________________________________________" Date: 3 August 2017" Monica Schmidt " " " " _______________________________________________________________________" Date: 3 August 2017" Zhongguo Xiong " " " " Final approval and acceptance of this dissertation is contingent upon the candidate’s submission of the final copies of the dissertation to the Graduate College. I hereby certify that I have read this dissertation prepared under my direction and recommend that it be accepted as fulfilling the dissertation requirement. ________________________________________________"Date: 3 August 2017" Dissertation Director: Peter J. Cotty " " 3" " STATEMENT BY AUTHOR This dissertation has been submitted in partial fulfillment of the requirements for an advanced degree at the University of Arizona and is deposited in the University Library to be made available to borrowers under rules of the Library. Brief quotations from this dissertation are allowable without special permission, provided that an accurate acknowledgement of the source is made. Requests for permission for extended quotation from or reproduction of this manuscript in whole or in part may be granted by the head of the major department or the Dean of the Graduate College when in his or her judgment the proposed use of the material is in the interest of scholarship. In all other instances, however, permission must be obtained from the author. SIGNED: Paul W. Kachapulula " " 4" " ACKNOWLEDGEMENTS I would like to thank my advisor Peter J. Cotty for his guidance, support and encouragement. Thank you for your wisdom and patience. Isaac Newton once said, “If I have seen further, it is by standing on the shoulders of giants”. Thank you for lifting me up. I am indebted to my committee: Drs. Barry M. Pryor, Marc J. Orbach, Monica Schmidt and Zhongguo Xiong. I have learned a lot from you all both in class and in committee meetings. I appreciate the time you dedicated to me. Thank you. To my friends and office mates Pummi, Lourena and Connel. Thank you for the laughs we shared. Thank you also for the debates we had on Aspergillus. To my friend Kennedy, thank you for accompanying me on those long drives collecting samples in Zambia. I thank God our paths crossed two decades ago. To Austin, thank you very much for all your technical assistance. Your hard work and outstanding work ethics helped me immensely. I am grateful to my wife for her love and support. It has been a tough road, but you have made it bearable. Thank you for your encouragement and for the numerous sacrifices you have made to help me complete my training. Mulena mulimu akufuyole ahulu. Nkwagala nyo! To God be all the praise! " " 5" " Paul W. Kachapulula is a fellow of the Norman E. Borlaug Leadership Enhancement in Agriculture Program Funded by USAID. " " 6" " DEDICATION To Josephine (Babyner), Martha (Mama), Paul Jnr. (Chubby) and Josephine (Pinshe). You four complete my life. I love you and thank God for you. " " 7" " TABLE OF CONTENTS! LIST OF FIGURES……………………………………………………………………...11 LIST OF TABLES………………………………………………………………………13 ABSTRACT……………………………………………………………………………..15 CHAPTER 1 - INTRODUCTION………………………………………………………17 CHAPTER 2 - AFLATOXIN CONTAMINATION OF GROUNDNUT AND MAIZE IN ZAMBIA: OBSERVED AND POTENTIAL CONCENTRATIONS ............ 20 Introduction……………………………………………………………………………20 Materials and methods .................................................................................................. 23 Study area .................................................................................................................. 23 Sampling .................................................................................................................... 23 Aflatoxin quantification in ground maize and groundnut ......................................... 26 Fungal isolation and identification ........................................................................... 29 Determining potential for aflatoxin formation after market ..................................... 29 Aflatoxin-producing ability of fungi from purchased crops ...................................... 30 Data analysis ............................................................................................................. 30 Results ........................................................................................................................... 32 Influences of agroecology and crop host on crop aflatoxin content ......................... 32 Aflatoxin formation after simulated poor storage ..................................................... 38 Association of community composition and aflatoxigenicity with increases in crop aflatoxin content after simulated poor storage .......................................................... 42 Aflatoxin-producing ability of fungi from purchased crops ...................................... 45 Discussion ..................................................................................................................... 50 Influences of agroecology on aflatoxin concentration .............................................. 50 Exposure to aflatoxins through consumption of maize and groundnut ..................... 52 Influences of fungal community structure on potential for crop contamination after market ........................................................................................................................ 53 " " 8" " CHAPTER 3 - ASPERGILLUS SECTION FLAVI COMMUNITY STRUCTURE IN ZAMBIA INFLUENCES AFLATOXIN CONTAMINATION OF MAIZE AND GROUNDNUT ..................................................................................................... 56 Introduction ................................................................................................................... 56 Materials and methods .................................................................................................. 59 Study area .................................................................................................................. 59 Sampling .................................................................................................................... 59 Isolation and identification of fungi from maize, groundnut and soils ..................... 62 Community composition of Aspergillus section Flavi from soils of cultivated and non-cultivated areas .................................................................................................. 62 Aflatoxin producing potential of A. parasiticus from cultivated fields and non- cultivated areas .......................................................................................................... 63 Data analysis ............................................................................................................. 64 Results ........................................................................................................................... 66 Fungi in maize and groundnuts ................................................................................. 66 Association between quantity of Aspergillus section Flavi and aflatoxin concentration ............................................................................................................. 73 Aspergillus section Flavi from cultivated and non-cultivated soils .......................... 76 Aflatoxin production by A. parasiticus from crops and soils .................................... 79 Discussion ..................................................................................................................... 83 Composition of Aspergillus section Flavi fungi in maize and groundnuts ................ 83 Association between quantity of Aspergillus section Flavi and aflatoxin concentration ............................................................................................................. 84 Aspergillus section Flavi from
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