Characterization of maize testing locations in eastern and southern Africa

Characterization of Maize Testing Locations in Eastern and Southern Africa. (May 2006) Francis Maideni, B.Sc., University of Malawi; M.S., Mississippi State University Chair of Advisory Committee: Dr. Javier F. Betrán The region of eastern and southern Africa is very diverse in environments and agronomic practices. The region has one of the highest per capita consumption of maize (Zea mays. L), which is predominantly produced by smallholder farmers. Some important constraints facing these farmers include drought and low fertility. For decades, the International Center for Wheat and Maize Improvement (CIMMYT) has been involved in developing maize genotypes that have high grain yields and are tolerant to drought, low fertility and other important constraints. This germplasm is developed for wide adaptation. However, the development of superior germplasm is significantly affected by interaction between genotypes and the environment (i.e., genotype by environment interaction, GEI). To estimate and understand GEI maize genotypes are evaluated in a range of environments representing as much variability of the target growing areas as possible. Because of dwindling resources needed to conduct testing in the region, it may not be possible to test in all potential target areas. Therefore, a careful process of site selection for testing is essential to improve efficiencies in cultivar testing and deployment. The objective of this research was to characterize the maize testing locations of the eastern and southern Africa region. Historical data from CIMMYT Regional Trials from 1999 to 2003 was used to characterize the environments and estimate genetic parameters. Environmnent and GEI showed consistently high contributions to the total variation observed among genotypes for grain yield. Environment contributed over 60% and sometimes up to 85% of total variation observed. Sequential retrospective pattern analysis (Seqret) was conducted on the adjusted standardized grain yield. A total of 7 groups of environments were identified. Repeatabilites, a measure of the proportion of phenotypic variation that is due to genetic differences, was reduced under stress conditions. The relationship among traits showed that anthesis-silking interval (ASI) is an important selective trait, which can improve selection efficiency for grain yield under stress iv conditions. Stability analysis provided an opportunity to observe the response and adaptation of genotypes to a wide range of environments. Variety ZM621 was a stable and high yielding genotype. v DEDICATION I would like to dedicate this work to my brother-in-law the late Mr. Frank Tony Chamanga. vi ACKNOWLEDGEMENTS I would like to thank Dr. Javier F. Betrán, my major professor and chairman of my graduate committee, for his guidance, and support not only in accomplishing this research work and doctoral level studies here at Texas A&M University but throughout my entire stay here in the United States of America. I would also like to thank the members of my graduate committee, Dr. William L. Rooney, Dr. Tim Murphy, Dr. C. Wayne Smith, for their guidance and constructive comments during the course of my studies. I would also wish to thank Dr. Wayne Jordan who initiated the project and the collaboration with CIMMYT, and was of great assistance to me before he handed over to Dr. Betran upon his retirement. As a Graduate Advisor, Dr. C. Wayne Smith demonstrated great patience, understanding, real and personal care, always exuded optimism and shown the highest level of professionalism, that we can all learn from, to him, thank you. I would also like to thank the Rockefeller Foundation, through Dr. Joe DeVries, for financially supporting my studies. At CIMMYT, I would like to thank Dr. Marianne Bänziger for all her support and encouragement throughout the research period especially during my stay at CIMMYT center in Harare, Zimbabwe. I would express my appreciation to my colleagues and fellow students at Corn Breeding and Genetics Laboratory, for their support, companionship and encouragement which assisted me the completion of this work. I would also like to acknowledge the love and understanding of my family during my stay and studies at Texas A &M University and during my stay in Harare, Zimbabwe. vii TABLE OF CONTENTS Page ABSTRACT. iii DEDICATION. v ACKNOWLEDGEMENTS. vi TABLE OF CONTENTS. vii LIST OF TABLES. ix LIST OF FIGURES. xiii CHAPTER