Design and Evaluation of Drought-Resistant Maize Varieties Through Conventional Breeding

Thesis Abstract

The increasing prevalence of drought conditions in maize-producing regions poses significant threats to food security, reducing crop yields and exacerbating economic instability among smallholder farmers. Addressing this challenge requires the development of maize varieties that exhibit enhanced drought tolerance through sustainable and accessible breeding techniques. This study aims to design and evaluate drought-resistant maize varieties using traditional hybridization and selection methods, focusing specifically on identifying high-yielding, drought-tolerant genotypes suitable for drought-prone environments. The primary objectives are to assess the genetic variability among selected maize germplasm, develop advanced drought-tolerant hybrids through controlled cross-breeding, and evaluate the agronomic performance and drought resilience of the newly developed varieties under field conditions. The research adopted a quantitative experimental research design, structured as a multi-stage breeding program complemented by field trials. The population comprised 120 diverse maize genotypes sourced from national germplasm banks, with a focus on drought-prone agro-ecological zones. A stratified random sampling technique was employed to select 60 elite parental lines exhibiting contrasting drought responses, which were used in controlled hybridization. The study involved successive generations of crossing and selection based on drought tolerance traits such as root depth, stay-green phenotype, and soil moisture retention capacity. Data collection instruments included field measurement tools for phenotypic traits, such as tensiometers for soil moisture analysis and spectrophotometers for chlorophyll content, alongside phenological and yield parameters recorded across two growing seasons. The reliability and validity of measurement instruments were ensured through calibration and pilot testing. Quantitative data were analyzed using analysis of variance (ANOVA) to determine significant differences among genotypes, alongside multivariate techniques like principal component analysis (PCA) to identify key traits associated with drought tolerance. Regression analysis explored relationships between phenotypic traits and yield performance, while heritability estimates informed the selection process. Expected findings include the identification of specific maize genotypes demonstrating significantly improved drought tolerance, characterized by deeper root systems, higher stay-green scores, and sustained grain yields under water-stressed conditions. The developed hybrids are anticipated to outperform existing commercial varieties, exhibiting superior stability and resilience during drought episodes. The study also expects to reveal the genetic correlations between drought-adaptive traits and yield components, providing insights into trait inheritance patterns vital for future breeding programs. This research contributes novel empirical evidence on the effectiveness of conventional breeding methods in enhancing drought tolerance in maize, highlighting the importance of phenotypic trait selection based on heritable and heritable-associated characteristics. The findings are expected to fill existing gaps related to genotype-by-environment interactions in drought-prone regions, informing breeders and policymakers on optimal selection strategies for climate-resilient maize production. The study's theoretical underpinning is grounded in the quantitative genetics framework, supported by the Breeder’s Equation, and contextualized within the stress-adaptation theory of plant resilience. The main conclusion emphasizes that targeted conventional breeding can produce drought-resistant maize varieties with significant yield stability in water-limited environments. Recommendations include scaling up successful genotypes for multilocation trials, integrating farmer participatory selection to enhance adoption, and further molecular characterization to complement phenotypic selection. Future studies should explore the integration of marker-assisted selection to accelerate drought tolerance breeding and evaluate the long-term performance and adaptability of the developed varieties under varying climatic conditions. Overall, the research underscores the vital role of traditional breeding techniques in addressing food security challenges posed by climate variability, contributing substantially to sustainable maize production systems.