Influence of environmental conditions on nutritional value of quality protein maize
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Date
2019-01
Authors
Shawa, Hilda Chilekeni
Journal Title
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Volume Title
Publisher
University of the Free State
Abstract
Maize is a staple crop to many people and it provides calorie, minerals and proteins to people in developing countries and globally. Quality protein maize (QPM) has improved nutritional quality but environmental conditions may have an effect on grain yield and nutritional content, especially under low nitrogen (N) conditions. The main objective of this study was to determine the influence of different production environments on nutritional quality and grain yield in QPM hybrids. This was done by grain yield assessment and nutritional quality analysis of QPM hybrids from CIMMYT-Zimbabwe, which were produced in different sites under low and optimum N conditions. The results for single analysis of variance (ANOVA) indicated that genotypes were significantly different for grain yield and all nutritional characteristics under low and optimum N. This was true except for oil content, phytic acid to iron molar ratio (MRFe) and phytic acid to zinc molar ratio (MRZn) at Harare (low N) and grain yield at Gwebi, phytic acid content, MRFe and MRZn at Glandel (optimum N). Combined ANOVA across optimum N locations were significantly different for genotypes, locations and genotype by environment interaction for all the traits, except for location effect for protein content. Negative correlations under both low and optimum environments were observed between α and γ zeins, β and γ zeins, and grain yield and Fe content. Principal component analysis biplots identified genotypes TH15938 and TH151082 to have high oil, phytic acid, γ zein and tryptophan contents in all environments. These characteristics were also positively correlated. Generally, low N reduced grain yield and nutritional quality characteristics. However, some specific genotypes were less sensitive to low N as it maintained grain yield (TH15976) and nutritional quality such as tryptophan (TH151082 and TH15895), oil (TH15938), total protein (Local check 1), Fe (TH15889) and Zn (Local check 1 and TH15851) contents. Alpha zein and phytic acid contents were reduced in most genotypes under low N conditions, suggesting increased tryptophan content, improved nutritional quality and micronutrient bioavailability under such conditions.
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Keywords
QPM, Non-QPM, Nutritional quality, Micronutrient bioavailability, Micronutrient deficiency, GEI, Genetic variation, Dissertation (M.Sc. (Plant Breeding))--University of the Free State, 2019