GENOTYPE BY ENVIRONMENT INTERACTION AND YIELD STABI LITY OF MAIZE HYBRIDS EVALUATED IN ETHIOPIA BY ABDURAHMAN BESHIR ISSA Submitted in the fulfilment of the requirements of th e degree Magister Scientiae Agriculturae (MSc. Agric.) In the Department of Plant Sciences/Plant Breeding Faculty of Agriculture and Natural Sciences University of the Free State Bloemfontein, South Africa July 2009 Supervisor: Prof. C.S. van Deventer Co-supervisor: Prof. M.T. Labuschagne i DECLARATION I, the undersigned, hereby declare that this thesis, prepa red for the degree of Magister Scientiae Agriculturae , which was submitted by me to the University of the Free State, is my original work and has not been submitted previously to any other University /Faculty. All sources of materials and financial assistances used for the study have been duly acknowledged. I furthermore cede copyright of the thesis in favour of the University of the Free State. Signed on the 31 th of July 2009 at the University of the Free State, Bloemf ontein, South Africa. ____________________________ ABDURAHMAN BESHIR ISSA ii ACKNOWLEDGEMENTS Praise be to Allah, the Cherisher and Sustainer of t he worlds, Most Gracious, Most Merciful! He has made the completion of this study a reality. I extend my sincere gratitude to the International Maize and Wheat Improvement Center (CIMMYT) for the financial arrangements of my study. P articularly, I want to express my indebtedness to Dr. Dennis K. Friesen, CIMMYT-Ethiopia l iaison officer, for all his supports and encouragement for the continuation of my postgraduate study. His follow up and assistances through out the study period is highly appreciated. The provision of essential supports and the grant of study l eave by the Ethiopian Seed Enterprise (ESE) is highly acknowledged. In this regard, I e xpress my gratefulness to Ato Getahun Alemu, former General Manager of ESE, and Ato Getachew Desta, Manager of Seed Production Department of ESE, for their motivation and assistance to advance my academic qualifications. I am also grateful to all other ESE staff who helped me in my study. The academic guidance and back-stopping from my supervisors Pr of. C.S. van Deventer and Prof. Maryke Labuschagne was indispensable for the sm ooth completion of the study. Hence, I would like to sincerely acknowledge Prof. van Deventer to have had the benefit of his mentorship and all-round advices. I also express my deepest gratitude to Prof. Maryke Labuschagne, my co- supervisor and head of the Plant Breeding Division, for her close supervision that resulted in a successful completion of the study. Prof Labuschagne’s passion for her students was my source of inspiration to decide and advance my study to a PhD. My a dmiration and thanks also goes to Mrs. Sadie Geldenhuys who handled for me the logistics and a ll the administrative tasks, so that I was able to concentrate more on my academics. I will alw ays remember the 2008/09 staff and students of Plant Breeding for their cooperation to have a fr iendly and enjoyable working atmosphere at the division. I would like also to sincerely acknowledge my colleagues an d collaborators at ESE-Addis Ababa and Awassa, Bako-National maize coordination proj ect and Upper Bir farm who contributed greatly in one way or another during the carry ing out of the research. This work would have been deterred with out the help of these individual s. My thanks are due to my brothers, sisters and relatives for their pious prayers and tender care for my family in my absence. I appreciate the support and patience of my wife Mrs. Zahra Jabir who tolerated the great responsibility of bringi ng up our kids Mohammed, Taha and A/Karim. To all of you I remain truthfully grateful an d would like to say Jazakumullah !! Finally, my stay in Bloemfontein was a great joy due to many brothers and friends, which I cannot list all the names. However, a few deserve specia l mention: my room mate Abe for all his goodness, Dagne, Birhane and Gobeze for their good company. I will not forget also the companionship of Rashad, Zaid, Dr. Khan and other UFS-MSA br others. iii TABLE OF CONTENTS Page Declaration i Acknowledgements ii Table of contents iii List of tables vi List of figures x Abbreviations xii 1. General Introduction 1 2. Literature Review 4 2.1 Origin of maize and its uses 4 2.2 Maize production in Ethiopia iv 2.5.4.5 Additive main effects and multiplicative interact ion method (AMMI) 31 2.6 Optimum allocation of resources 34 2.7 References 35 3. Assessment of genotype x environment interaction and gra in yield evaluation of Ethiopian maize hybrids 42 3.1 Abstract 42 3.2 Introduction 43 3.3 Materials and methods 44 3.3.1 Materials 44 3.3.2 Methods 45 3.3.2.1 Description of the experimental sites 45