Maize Genomics and Genetics 2025, Vol.16, No.1, 10-19 http://cropscipublisher.com/index.php/mgg 12 3 Experimental Design in Maize Evaluation 3.1 Selection criteria for maize lines The selection of maize lines for this study was based on multiple criteria, focusing on quality, stress resistance, and yield. Quality traits included kernel size, sweetness, and nutritional content such as zinc and provitamin A levels. For instance, the study by Matongera et al. (2023a) highlighted the importance of stacking nutritional traits like zinc and provitamin A to enhance the overall quality of maize. Additionally, the evaluation of quality protein maize (QPM) lines under various stress conditions was emphasized to ensure the selection of lines with superior nutritional profiles (Chiuta and Mutengwa, 2020). Stress resistance was another critical criterion, with a focus on drought and heat tolerance. The study by Chen et al. (2012) identified maize inbred lines that maintained high leaf relative water content and vegetative growth under drought conditions, which were crucial indicators of drought tolerance. Similarly, the ability to withstand high temperatures was assessed, with lines showing enhanced tolerance being prioritized for selection. The integration of these stress resistance traits ensures the development of resilient maize lines capable of thriving under adverse environmental conditions. Yield performance was also a key selection criterion. The study by Lu et al. (2012) evaluated grain yield and its components under both well-watered and water-stressed environments, identifying stable traits such as kernel weight that remained consistent under drought stress. High-yielding lines were selected based on their performance across different stress and non-stress conditions, ensuring the development of maize lines with robust yield potential (Menkir et al., 2020). 3.2 Experimental setup The field experiment was designed using a randomized plot arrangement to ensure unbiased results and scientific reliability. Each maize line was planted in a randomized complete block design (RCBD) with three replications to account for environmental variability and enhance the accuracy of the results. This design was chosen to minimize the effects of spatial heterogeneity and ensure that the observed differences in performance were due to genetic factors rather than environmental influences (Chiuta and Mutengwa, 2020). The experimental plots were established under both stress and non-stress conditions to evaluate the performance of maize lines across different environments. Stress conditions included managed drought stress, heat stress, and low nitrogen stress, while non-stress conditions involved well-watered and optimal nutrient environments. For instance, the study by Matongera et al. (2023b) utilized a similar approach, evaluating maize lines under various stress and non-stress environments to assess their yield stability and adaptability. The use of multiple environments allowed for a comprehensive assessment of the maize lines' performance and ensured the selection of lines with broad adaptability (Abu et al., 2021). 3.3 Evaluation metrics The evaluation of maize quality involved several metrics, including sweetness, kernel size, and nutritional content. Sweetness was assessed using sensory evaluation and Brix measurements, while kernel size was measured using calipers to determine the average kernel diameter. Nutritional content, such as zinc and provitamin A levels, was analyzed using spectrophotometric methods. The study by Matongera et al. (2023a) emphasized the importance of these quality traits in the selection of superior maize lines, highlighting the need for comprehensive evaluation to ensure the development of high-quality maize varieties. Stress resistance was evaluated using metrics such as heat and drought tolerance. Drought tolerance was assessed by measuring leaf relative water content, chlorophyll content, and normalized difference vegetation index (NDVI) before and after drought stress application. The study by Lu et al. (2012) demonstrated the reliability of NDVI as an indicator of drought tolerance, with significant correlations observed between NDVI and grain yield. Heat tolerance was evaluated through field observations following major heat events, with lines showing minimal damage to reproductive tissues being considered heat-tolerant (Chen et al., 2012).
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