Evaluation of drought tolerance in maize hybrids using physiological and molecular markers under rainfed conditions

Project Abstract

Drought stress is a major constraint to maize productivity in rainfed agroecosystems, necessitating the identification of hybrids with robust tolerance mechanisms. This study evaluates physiological and biochemical responses, as well as molecular marker associations, to elucidate the contribution of diverse maize hybrids to drought adaptation under water-limited conditions. A diverse set of maize hybrids was evaluated under controlled drought and well-watered environments across two growing seasons in field conditions representative of rainfed agriculture. Key physiological parameters including relative water content, leaf water potential, photosynthetic rate, stomatal conductance, transpiration, chlorophyll fluorescence, and membrane stability were measured at critical growth stages. Biochemical analyses assessed osmolyte accumulation (proline, soluble sugars), antioxidant enzyme activities (superoxide dismutase, catalase, ascorbate peroxidase), malondialdehyde content as an index of lipid peroxidation, and non-enzymatic antioxidants such as ascorbate and glutathione. Leaf osmotic adjustment and root-shoot biomass partitioning were examined to understand access to deep soil moisture and allocation patterns under drought. Simultaneously, a targeted molecular approach using a panel of stress-associated single nucleotide polymorphisms (SNPs) and candidate genes linked to drought tolerance (such as those governing ABA signaling, root architecture, and osmolyte biosynthesis) was conducted to identify marker-trait associations. Data were analyzed using a mixed-model framework to partition genetic, environmental, and genotype-by-environment interaction effects, with heritability estimates computed for key traits. Multivariate analyses, including principal component analysis and cluster analysis, were employed to identify drought-tolerant hybrids exhibiting stable performance across environments. The integration of physiological, biochemical, and molecular data enabled the construction of a predictive model for drought tolerance, highlighting hybrids that maintain photosynthetic efficiency and membrane integrity while sustaining osmotic adjustment and antioxidant defense under water deficit. Significant correlations were observed between relative water content, chlorophyll fluorescence, and grain yield under drought, reinforced by strong associations with SNP markers in loci related to ABA signaling and root development. Hybrids displaying superior drought tolerance demonstrated lower yield loss, higher water-use efficiency, and more robust antioxidant responses, suggesting a multifaceted defense involving stomatal regulation, efficient water extraction, and effective ROS scavenging. The findings provide practical implications for breeding programs by recommending a marker-assisted selection strategy that combines physiological screening with molecular marker profiles to accelerate the development of drought-resilient maize cultivars for rainfed systems. This integrated approach offers a robust framework for predicting field performance under drought and for dissecting the relative contributions of physiological and molecular mechanisms to maize drought tolerance.

Project Overview

What This Project Is About

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A straightforward study that looks at how different maize varieties cope with drought when grown with limited water. It combines simple measurements of plant health with some laboratory checks to see which varieties perform best during dry periods.

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The Problem It Addresses

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Drought reduces maize yields, threatening food supply and farmer income. Farmers need reliable signs (traits) that show which hybrids handle dry conditions well so they can choose the best seeds for rainfed farming.

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Objectives of the Project

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1. Identify maize hybrids that show better growth under drought.
2. Link easy field observations with internal stress indicators.
3. Explain how physiological traits relate to yield under water shortage.
4. Provide practical guidance for farmers and breeders on drought-tolerant options.

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What You Will Do Step by Step

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1) Review basic drought concepts and set up a field trial with several maize hybrids. 2) Grow plants under normal and limited-water conditions. 3) Measure visible traits like plant height, leaf wilting, and biomass. 4) Collect simple tissue samples for basic molecular markers (explained simply). 5) Analyze which hybrids perform best under drought and how markers relate to performance. 6) Summarize findings in clear recommendations.

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Expected Outcome

Clear identification of drought-tolerant maize hybrids and a simple link between field performance and molecular indicators, offering practical options for growers and breeders to improve rainfed maize production.