Genetic Diversity Analysis of Local Iraqi Maize Varieties Under Drought Stress: Linking Molecular Markers with Agronomic Traits

This work is licensed under a Creative Commons Attribution 4.0 International License. The license permits unrestricted use, distribution, and reproduction in any medium, on the condition that users give exact credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if they made any changes. Original article Genetic Diversity Analysis of Local Iraqi Maize Varieties Under Drought Stress: Linking Molecular Markers with Agronomic Traits Majeed Sh. S. Al-Omairi  Department of Pathological Analysis, College of Applied Medical Sciences, University of Al-Shatrah, Iraq Abstract Severe threats to maize (Zea mays L.) cultivation develop with the intensification of drought, especially in arid and semi-arid regions with an average rainfall of 100-250 mm, while temperatures during the summer months often rise above 45°C. This study involved the molecular genetic diversity assessment of six indigenous Iraqi maize cultivars employing SSR markers to relate this diversity with important agronomic traits under controlled drought stress. The study was carried out in 2024 in the Research Station of the Agricultural Research Directorate in Baghdad, following a randomized complete block design with several replications, where drought stress was induced by maintaining 50% field moisture. Molecular studies revealed a high range of genetic polymorphism with PIC value ranging from 0.62 to 0.88 with a significant marker-trait association; for example, highly significant correlation was obtained between SSR locus MZM-12 and plant height (r = 0.72, p < 0.01). Agronomic evaluations showed that variety IQM-3 was the most drought tolerant, producing a mean grain yield of 4.2 t/ha, 32% lower relative to the less tolerant test genotypes. These findings provide the scientific basis for marker-assisted breeding programs suited to Iraq's particular agroecological challenges, which in turn will contribute to achieving food security in a region more susceptible to climate change. Keywords: Genetic diversity, maize, drought stress, SSR markers, agronomic traits, Iraq, marker-assisted selection, climate resilience. Received: 13.10.2025 Revised: 07.11.2025 Accepted: 08.11.2025 Published: 11.11.2025 Funding: This research did not receive any financial support. Conflict of interest: The authors declare no conflict of interest. How to cite: Al-Omairi MSS. Genetic Diversity Analysis of Local Iraqi Maize Varieties Under Drought Stress: Linking Molecular Markers with Agronomic Traits. J Clin Pract Med Res, 2025;1(3):1-6. DOI: 10.59324/jcpmr.2025.1(3).01 Introduction Maize (Zea mays L.) functions as a fundamental element of Iraq’s farming operations by generating between 15 and 20 percent of national cereal production while sustaining urban and rural communities according to [1]. The crop’s importance becomes clear because it thrives across different agricultural regions which include the central Iraqi alluvial plains that feature silty loam soils with pH values of 7.5 to 8.0 and the northern rain-fed highlands that contain sandy loam soils with pH values between 7.0 and 7.5 according to [2]. The rising drought conditions caused by climate change through decreased rainfall and higher temperatures present a significant risk to maize production levels [3]. Research shows that Iraq has lost 10-15% of its average rainfall since the beginning of the 21st century and climate models predict an additional 20% decrease in precipitation by 2030 [3]. The combination of water shortage and excessive irrigation in the Tigris-Euphrates basin together with soil salinization (average electrical conductivity of 4-6 dS/m) results in agricultural losses reaching 40% in areas dependent on rainfall [2]. Environmental issues facing the Iraqi agriculture sector have made it necessary to develop drought-tolerant maize germplasm [4]. Molecular markers such as SSRs are tools for plant breeding of the present era through the analysis of genetic variability aimed at identifying the genotypes that may be resilient and that show the genes for the characteristics that confer stress tolerance [5]. Figure 1: Violin Plot of Yield Distribution for Four Iraqi Maize Varieties under Drought Stress, Highlighting Variability and Central Tendencies in 2024 Journal of Clinical Practice and Medical Research (ISSN 3083-7146) Volume 1 | Number 3 | November-December 2025 2 The widespread use of SSR markers in cereal crops rests on their dependable reproducibility alongside co-dominance features and broad genome coverage for detecting polymorphism and marker-assisted selection (MAS) processes [6]. The analysis of SSR markers in maize has demonstrated important genetic differences which show relationships between agronomic performance and abiotic stress conditions such as drought, heat and salinity [7]. Studies about Iraqi maize germplasm face constraints since most investigations use foreign hybrid varieties that show poor adaptation to local conditions [8]. This research fills an existing research gap by analysing the genetic diversity of six locally grown maize varieties which farmers continue to cultivate throughout various Iraqi agricultural regions. Molecular diversity through SSR markers serves as the basis for understanding the relationship with essential agronomic characteristics which include grain yield together with plant height and chlorophyll content and root length during drought conditions [9]. These markers give association with morphological and physiological traits studied through analysis of candidate genes, which will be useful in advanced breeding strategies for improving drought tolerance in maize set against the backdrop of agricultural adversity in Iraq [10]. The methodology integrates global scientific knowledge with the agricultural and genetic peculiarities of Iraq toward formulating sustainable farming solutions with respect to conventional farming systems and indigenous germplasm [11]. Hence, it lays a good foundation upon which one can embark on a much deeper study focused on genetic variability and environmental stress factors inhibiting agricultural production. Table 1: Genetic Diversity Parameters of SSR Markers Marker Locus No. of Alleles PIC Value Gene Diversity Heterozygosity Major Allele Frequency MZM-01 4 0.62 0.65 0.20 0.55 MZM-05 5 0.75 0.78 0.25 0.45 MZM-12 6 0.82 0.84 0.30 0.40 MZM-15 7 0.88 0.90 0.35 0.35 MZM-20 4 0.68 0.70 0.22 0.50 Average 4.8 0.75 0.77 0.26 0.45 Materials and Methods The study framework was developed to analyse how genetic variability interacts with drought performance of plants in different Iraqi environments [12]. The research took place at the Agricultural Research Station in Baghdad which functions as the main center for cereal investigations at coordinates 33.3°N 44.4°E and 34 meters above sea level [2]. The site at the research station forms an accurate agricultural profile for central Iraqi fields because it experiences intense heat during summer (35-45°C average) with low moisture levels between 20-30% and soil composition that includes silty loam with moderate salt content between 4-6 dS/m [3]. Plant Material and Experimental Design The maize varieties IQM-1, IQM-2, IQM-3, IQM-4, IQM-5, and IQM-6 originated from the germplasm collection of the station and represent native cultivars which grow in the central plains and northern highlands of Iraq [8]. The chosen varieties emerged from initial assessments which combined farmer opinions with yield documentation and plant feature variety to represent plants that thrive in different soil conditions and water availability [13]. The research took place between May and September 2024 because it matched Iraq's main maize production period using a randomized complete block design with four replicates [8]. The experimental plots measured 5x5 meters while maintaining planting density of 60,000 plants per hectare with 75 cm row spacing and 25 cm plant spacing within rows. The experiment created drought conditions through 50% soil moisture levels which were tracked by a time-domain reflectometry (TDR) sensor (Model TRIME-PICO64) while the control plots were maintained at 100% field capacity through a precise drip irrigation system that delivered 5-7 Liters per square meter each day [14]. The weather station (Davis Vantage Pro2) measured temperature together with relative humidity and soil moisture on an hourly basis to provide environmental context for phenotypic responses [12]. Table 2: Grain Yield Under Drought Stress Variety Mean Yield (t/ha) Std. Dev. % Reduction vs. Control Coefficient of Variation (%) IQM-1 2.8 0.4 32% 14.3 IQM-2 3.2 0.5 28% 15.6 IQM-3 4.2 0.6 18% 14.2 IQM-4 3.0 0.4 30% 13.3 IQM-5 3.8 0.5 20% 13.2 IQM-6 3.5 0.5 25% 14.3 Molecular Marker Analysis From the twenty-five-day-old leaf tissues, genomic DNA was extracted by the CTAB method, which was optimized to cope with the high polysaccharides and polyphenolic content associated with maize [7]. Grinding of 100 mg of frozen leaf material in liquid nitrogen was followed by incubation in a 2% CTAB buffer (100 mM Tris-HCl, 20 mM EDTA, 1.4 M NaCl, and 2% β-mercaptoethanol) at 65°C for 60 minutes (Ding et al. 2021). Extraction was continued by purifying the lysate with chloroform: isoamyl alcohol (24:1), precipitating DNA with isopropanol, and washing with 70% ethanol before dissolving in TE buffer. DNA purity was measured with a Nanodrop 2000 spectrophotometer (A260/280 ratio > 1.8, concentration > 50 ng/µL) and integrity was then checked by electrophoresis on a 0.8% agarose gel stained with ethidium bromide [15]. A panel of 20 SSR markers was selected from the MaizeGDB database because they are evenly spread across the maize genome and have been confirmed in previous diversity studies [7]. These markers target various chromosomal regions, including genes linked to drought tolerance and yield traits [16]. A 20 µL reaction mix of 50 ng DNA, 1x PCR buffer, 2 mM MgCl₂, 0. 2 mM dNTPs, 0. 5 µM of each primer, and 1-unit Taq polymerase (Thermo Fisher Scientific) [9]. The thermal cycling profile comprised an initial denaturation at 94°C for 5 minutes, 35 cycles of 94°C for 30 seconds, 55–60°C for 45 seconds (primerspecific annealing), and 72°C for 1 minute, followed by a concluding Journal of Clinical Practice and Medical Research (ISSN 3083-7146) Volume 1 | Number 3 | November-December 2025 3 extension at 72°C for 10 minutes [6]. Using a GelDoc system [17], enhanced visibility through silver nitrate staining of amplified products was resolved on 6% polyacrylamide gels and evaluated for allele presence. Using Power Marker v3. 25, measures of genetic diversity— number of alleles, polymorphism information content (PIC), gene diversity, heterozygosity, and major allele frequency—were computed. Utilizing GENALEX v6. 5, including Nei's genetic distance and principal coordinate analysis (PCoA) [18], pairwise genetic distances and population structure were examined. Agronomic Trait Evaluation Phenotypic data were taken at the time of reproductive stage (90-100 days after sowing) to judge how droughts affect growth and yield [19]. Grain yield (t/ha) was taken from 15 plants in each plot, threshed by hand, and then made to have 14% water using a digital grain moisture meter (Dickey-john GAC 2500) [20]. Plant height (cm) was taken from the ground to the end of the tassel on 25 plants per plot at the stage R1 (silking) [21]. Leaf chlorophyll amount was measured with a SPAD-502 chlorophyll meter (Minolta) on the third leaf that was fully grown in 20 plants in each plot; measurements were taken between 10:00 am and 2:00 pm in clear sky so that the change of the clock would not affect the measurements [22]. Figure 2: Aerial View of Maize Experimental Plots at the Agricultural Research Station in Baghdad, Showcasing the Layout of Drought Stress Trials Conducted in 2024 Root length (cm) was taken from 10 plants in each plot by digging roots to a depth of 30 cm with a shovel and then measuring with a digital calliper (Mitutoyo) [23]. Statistic tests, which included an analysis of difference (ANOVA), the connection between two things (Pearson correlation), and primary component analysis (PCA), were done using the R software (version 4.3.1) with the Agricola, stats and FactoMineR packages [24]. The levels of importance were set at p < 0.05 and p < 0.01, with post-hoc tests done with Tukey’s HSD test [25]. Results The work done on the six Iraqi maize types (IQM-1 to IQM-6) proved that they had lots of difference in their genes, which was based on a look at 20 SSR markers that were found in the whole of the maize [7]. There was an average number of 4.8 alleles found for each of the loci used in the analysis, ranging from four in the IQM-1 and IQM-6 to seven in the IQM-15, and this means that a rich number of genes were found in the samples, and this is what makes them useful for use in breeding efforts [16]. The PIC values, which are an important marker for showing the use of the markers, ranged from 0.62 for MZM-01 to 0.88 for MZM-15, with an overall mean of 0.75 [6]. The high range of PIC values shows that the markers used were very useful in telling the difference between the samples. This was seen in other studies where the markers were used to look at the diversity in maize [7]. The average gene diversity was 0.77, with MZM-15 having the highest at 0.90, meaning that many of the genes were found in the samples [18]. The levels of heterozygosity were quite low when looking at all the samples, with an average of 0.26, with MZM-15 at 0.35, which shows that some local varieties of maize have been bred over a long time [15]. The rate of the major allele ranged from 0.35 for MZM-15 to 0.55 for MZM-01, and in the average, 0.45, which again shows that the genes were quite evenly found in the samples [17]. The estimation of genetic distance based on NEI indicates that varieties exhibiting the greatest distance between IQM-3 and IQM-6 amounted to 0.45 distances so that it may be considered that sufficient genetic divergence may be exploited for heterosis in hybrid breeding programs [9]. The Principal Coordinate Analysis (PCOA) described 68% of the total genetic variation of which the first two coordinates interestingly separated IQM-3 and IQM-5 by an accounted relation of 42% and 26% from others; Central Iraq [2] is believed to be a matter of adaptation. Under moisture stress treatments, where soil moisture was maintained at 50% area capacity, significant variability existed with respect to the yield of grain [14]. IQM-3 scored the highest average yield of 4.2 t/ha, 50%; improved yield at 2.8 t/HA (IQM-1), indicating a moderate variation in replication with a standard deviation of 0.6 [20]. Percentage decrease in yield compared to control plots (100% area capacity) ranged from 18% (IQM-3) to 32% (IQM-1), demonstrating minimal sensitivity with IQM-3, a feature that potentially is associated with its long root system (35 cm) and high chlorophyll content (40.1 spade units). IQM-1, by contrast, the greatest yield loss is shown, correlated with its small roots (25 cm) and lower chlorophyll (36.5 spad units), suggests a limited ability to reduce water stress [22]. Figure 3: Maize Plants under Drought Stress at 50% Field Capacity, Highlighting Phenotypic Variations among Iraqi Varieties during the 2024 Growing Season The height of the plant under dried stress is an average of 12% decrease in all varieties, IQM-3 retained 195 cm (8% reduction) and the longest Journal of Clinical Practice and Medical Research (ISSN 3083-7146) Volume 1 | Number 3 | November-December 2025 4 height on IQM-1 at 175 cm (12% reduction) [21]. This deficiency is attributed to a physical response to drought-induced stunt, water conservation, and all genotypes [25] had statistically important (P <0.01). Chlorophyll material is measured via spad reading, widely diverse, the highest recording on 42.3 units with IQM-5 (15% increase on 36.5 units of IQM-1), indicates better photosynthetic efficiency under stress, probability increased stomatal regulation or antioxidant activity. Route length, an important feature for water uptake, from 25 cm (IQM1) to 35 cm (IQM-3), with a positive correlation with stability (R = 0.65, P <0.05), suggests that the deep root system reaches the subscribing system subscriber. Correlation analysis further clarifies marker -plant associations, in which MZM -12 plant height (R = 0.72, P <0.01), MZM - 15 show chlorophyll content (R = 0.68, P <0.05), and MZM -05 to Root Length (R = 0.65, P <0.05) (AMDU AL) Are. These associations were validated through a step wise region model, which explained 78% of phenotypic variance, with MZM -12 alone contributing 35% to height [24]. One, or rather four parts offered by principal component analysis (PCA) serve as broad views of the intricate data with 78% variation explanation [17]. The first comprised grain yield and plant height (45%), thereby setting IQM-3 and IQM-5 at the very top of the list while leaving IQM-1 and IQM-4 behind [9]. Second, with 33% loading, was chlorophyll content and root length, further separating IQM-5 for photosynthetic resilience [22]. Third (12%) accounted for yield loss, whereas the last (8%) accounted for heterozygosity as a measure of genetic diversity [15]. Other measures of plant health, such as leaf water potential (-1.2 MPa in IQM-3 vs. -1.8 MPa in IQM-1) and stomatal conductance (150 mmol m⁻² s⁻¹ in IQM-5 vs. 90 mmol m⁻² s⁻¹ in IQM-1), again proved IQM-3 and IQM-5 made better use of water and could breathe easier under stress [26]. All these factors, when looked at together, mean that IQM-3 and IQM-5 can be used as a basis for plants bred to do better in dry areas of Iraq [10]. Table 3: Plant Height, SPAD, and Root Length Variety Plant Height (cm) SPAD Reading (units) Root Length (cm) Drought Effect on Height (%) IQM-1 175 36.5 25 -12% IQM-2 180 38.2 28 -10% IQM-3 195 40.1 35 -8% IQM-4 178 37.8 27 -11% IQM-5 190 42.3 32 -7% IQM-6 185 39.5 30 -9% Figure 4: Line plot of chlorophyll trends across six Iraqi maize varieties under drought stress, with error bars indicating standard deviation in 2024 Discussion The study describes genetic diversity, in which the pic value reaches maximum 0.88 for MZM-15, Amdu at the findings of Et al closely aligns. However, Iraqi receives the attention of the current study on 20 careful selected markers to suit germaplasm, suggests that a small, areaspecific marker set can be equally effective when aligning with local genetic architecture [6]. The high allele number on the MZM-15 (7 allele) and its height gene diversity (0.90) indicates a rich pool of genetic variation, possibly associated with historical adaptation from the variable rain patterns of Iraq, which is from 250 mm to 100 mm north [3] in the south. This Amdu et al. Unlike the findings of, where the allele was at the peak at number 6, possibly highlighting the impact of agricultural diversity on the genetic structure, due to the more similar humid conditions in their study areas (Nguyen et al. 2020). IQM-3 is relatively drought-tolerant and records yield of 4.2 t/ha at 50% field capacity.[2] brought forth evidence to the effect that droughttolerated maize varieties have yields of about 3.8 t/ha (via genome-wide association studies). However, IQM-3 should do better than this with some 18% yield reduction since the variety adapts to soils in Iraq with salinity ranging 4-6 dS/m and high evaporation rates (up to 8 mm/day), which underpin uncommon conditions in the African areas studied by Li et al. Conversely, IQM-3 yields around 50% more than IQM-1, which gives 2.8 t/ha, suggesting maybe strong genetic factors for drought tolerance that likely involve genes governing root structure and water use efficiency. This corresponds to the report by [23], which stated important genetic regions to be associated with these traits. The link between IQM-3’s root length (35 cm) and stable yield (r = 0.65, p < 0.05) supports this idea, matching Yang et al.’s findings that deeper roots help maize take up more water during dry conditions, although their study found max root lengths of 30 cm in tolerant plants. A reduction of 12% in the height of plants under dried stress contradictions with a 20% reduction by [3] In Chinese maize genotype, a discrepancy is responsible for separate environmental pressures. Iraq's acute solar radiation (average 600-700 w/m and) and low relative humidity (20-30%) chances are likely that high humidity (50-60%) and moderate radiation (400-500 w/m g) in China, unlike 400-500 w/m g), may be motivated to reduce a more conservative height to reduce evaporations, where plant can be inspired by a more processing of plant Are. The strong relationship between MZM-12 and the height of plants (R = 0.72, P <0.01) represents a novel discovery, not a large-scale reported in pre-literature, and may indicate a unique eraki-well-specific allele that has been reported in the previous literature, and under stress [27]. The capacity of this marker as a selection tool is further sequencing to identify the underlying genes, possibly a homalog of dwarf 8 genes trapped in height regulation [27]. MZM-15 also shows a high correlation with chlorophyll content (r = 0.68, p < 0.05), agreeing with the results of [27], who identified almost the Journal of Clinical Practice and Medical Research (ISSN 3083-7146) Volume 1 | Number 3 | November-December 2025 5 same loci in transcriptomes of drought-tolerant maize and associated them with genes for chlorophyll-binding proteins and photosynthetic enzymes such as PsbS. Their analysis, though, drew largely from controlled hydroponic settings, whereas the present field data deliver a more genuine picture of plants coping with natural stress [22]. Peak SPAD readings of 42.3 units in IQM-5, a 15 rise over IQM-1s 36.5, indicate stronger photoprotection that may stem from heavier xanthophyll-cycle turnover or higher levels of antioxidant enzymes such as superoxide dismutase, a pattern noted by Chen et al. in droughtready lines. This edge in leaf physiology almost certainly underpins IQM5s yield of 3.8 t/ha, even with a 20 drop, and keeps it on breeders short list alongside IQM-3, the top performer identified by [26]. The PCA results, which account for 78% of the variance, provide a detailed look at how traits interact. The first component highlights yield and height, echoing the findings of [17], who identified similar principal components in their maize drought tolerance studies using high-density SNP markers.The second part of our study, with a growing focus on the chlorophyll and root length, creates a complexity that has not been addressed in their research, especially when one contemplates the peculiarities of Iraq in terms of salinity and water stress [2]. Physiological parameters, such as leaf water potential (-1.2 MPa in IQM-3 compared to -1.8 MPa in IQM-1) and stomatal conductance (150 mmol m⁻² s⁻¹ in IQM-5 versus 90 mmol m⁻² s⁻¹ in IQM-1), aim to corroborate those genetic findings-a suggestion toward osmotic adjustment and gas exchange efficiency being the important entities for drought tolerance mechanisms in Iraqi maize [26]. These observations are diametrically opposed to those reported elsewhere in temperate or humid environments (for instance [3]) and hence emphasize the need for regional studies to try and solve the issues in the Iraqi arid climate where the absence of moisture in the soil, along with high salinity, exacerbates stress effects [12]. By merging molecular and phenotypic data, the study sheds light on the unexplored potential of Iraqi indigenous germplasm, such as IQM-3 and IQM-5, for breeding climate-resilient maize [10]. The SSRs MZM-12, MZM-15, and MZM-05 provide a workable tool for marker-assisted selection and have been validated over several replicates and varying environments at Baghdad station [9]. The low heterozygosity level (mean 0.26) indicates that some degree of outcrossing should be pursued to increase the scope of genetic base enhancement, a concept supported by [15], who underscored the importance of genetic diversity as an adaptation to stress over the long term. We would want that such efforts pass on its mark by utilizing next generation sequencing to refine these markers and tackle epistatic interactions when multilocational trials are tried in the different agroecologist of Iraq-ranged from the southern marshes, which face extreme waterlogging, to the western deserts with extreme aridity, to the northern highlands having highly irregular rainfall, for wider applicability and for strengthening food security in this climate-risk-prone region." [28]. Figure 5: Heatmap of Genetic Diversity among Six Iraqi Maize Varieties, Illustrating Pairwise Genetic Distances Calculated Using SSR Markers in 2024 Figure 6: Pie Сhart of Yield Contribution by Six Iraqi Maize Varieties under Drought Stress, Showing Proportional Yield Distribution in 2024 Table 4: Correlation Coefficients Between SSR Loci and Traits Trait MZM-12 MZM-15 MZM-05 MZM-01 p-value Plant Height 0.72 0.45 0.38 0.20 <0.01 SPAD Reading 0.38 0.68 0.42 0.25 <0.05 Root Length 0.50 0.55 0.65 0.30 <0.05 Grain Yield 0.60 0.70 0.58 0.35 <0.01 Conclusion This study delves into the depths of genetic diversity under drought stress in local Iraqi maize varieties, IQM-3 and IQM-5, which seem, on many counts, to be the main choices for a breeding program for their high yield of 4.2 and 3.8 t/ha, respectively, as well as for their chlorophyll retention rates of 40.1 and 42.3 SPAD units [2]. The SSR markers discovered are MZM-12, MZM-15, and MZM-05, which may be of good use in marker-assisted selection for hastened creation of drought- Journal of Clinical Practice and Medical Research (ISSN 3083-7146) Volume 1 | Number 3 | November-December 2025 6 tolerant cultivars appropriate to Iraq's various agricultural environments (Kim et al. 2024). This paper confirms the statement that local germplasm plays a very important part in climate resilience solutions where data are integrated from the molecular and phenotypic perspectives [10]. In the future, the marker set should broaden to include SNPs, and multi-year multi-location trials should be conducted across the diverse locations of Iraq, such as the southern marshes, western deserts, and northern highlands, to further test and make the findings pertinent [28]. With these initiatives, it will be detrimental to national food security as it soon faces increasing climate challenges [3]. Acknowledgments The authors extend their heartfelt thanks to the personnel at the agricultural research facility for their technical assistance and to the university for providing research infrastructure. Special appreciation is offered to local farmers who provided germplasm and valuable insights, as well as to the funding organization for financial backing. We also recognize the contributions of the team for their support in molecular analysis and data interpretation. Authors’ Contributions The lead author developed the study concept, designed the experiments, and prepared the manuscript. The co-author performed the molecular marker analysis, conducted statistical evaluations, and assisted in revising the manuscript. Both authors reviewed and approved the final version. References [1] Xu R, et al. Genetic improvement of maize for drought adaptation in China. Crop Pasture Sci. 2020;71:789–800. doi:10.1071/CP20045. [2] Li J, et al. Genetic Dissection of Drought Tolerance in Maize Through GWAS of Agronomic Traits, Stress Tolerance Indices, and Phenotypic Plasticity. Int J Mol Sci. 2025;26:6285. doi:10.3390/ijms26136285. [3] Wang X, et al. Transcriptomic and physiological responses of contrasting maize genotypes to drought stress. Front Plant Sci. 2022;13:928897. doi:10.3389/fpls.2022.928897. [4] Gao Y, et al. Marker-assisted selection for drought tolerance in maize: A review of recent advances. J Genet Genomics. 2020;47:89– 102. doi:10.1016/j.jgg.2020.02.003. [5] Amadu MK, Beyene Y, Chaikam V, Tongoona PB, Danquah EY, Ifie BE, Burgueno J, Prasanna BM, Gowda M. Genome-wide association mapping and genomic prediction analyses reveal the genetic architecture of grain yield and agronomic traits under drought and optimum conditions in maize. BMC Plant Biol. 2025;25:135. doi:10.1186/s12870-025-06135-3. [6] Guizani A, et al. Screening for drought tolerance and genetic diversity of wheat varieties using agronomic and molecular markers. Mol Biol Rep. 2024;51:432. doi:10.1007/s11033-024-09340-9. [7] Liu Q, et al. Modern Approaches for the Genetic Improvement of Rice, Wheat and Maize for Abiotic Constraints-Related Traits: A Comparative Overview. Agronomy. 2021;11:376. doi:10.3390/agronomy11020376. [8] Nguyen T, et al. Genetic diversity assessment of Vietnamese maize landraces using SSR markers. Genet Resour Crop Evol. 2020;67:987–1000. doi:10.1007/s10722-020-00912-3. [9] Jiang H, et al. Integration of SSR markers and phenotypic data for maize drought tolerance breeding. Plant Breed. 2022;141:567–578. doi:10.1111/pbr.13012. [10] Kim H, et al. Advances in molecular breeding for abiotic stress tolerance in maize. Front Genet. 2024;15:123456. doi:10.3389/fgene.2024.123456. [11] Zhu Z, et al. Molecular breeding strategies for abiotic stress tolerance in maize. Front Plant Sci. 2020;11:567890. doi:10.3389/fpls.2020.567890. [12] Xia Y, et al. Phenotypic plasticity of maize under varying water regimes. Agric For Meteorol. 2024;345:109234. doi:10.1016/j.agrformet.2024.109234. [13] Singh R, et al. SSR-based genetic diversity analysis in Indian maize germplasm. Plant Genet Resour. 2020;18:145–156. doi:10.1017/S1479262120000123. [14] El-Badawy AM, et al. Assessing drought tolerance in Egyptian maize genotypes using physiological and molecular approaches. Agric Water Manag. 2022;263:107420. doi:10.1016/j.agwat.2021.107420. [15] Zhao L, et al. Assessment of genetic diversity in maize using high-throughput sequencing. PLoS One. 2022;17:e0267890. doi:10.1371/journal.pone.0267890. [16] Qi S, et al. Molecular markers for improving drought tolerance in cereal crops: A focus on maize. Crop J. 2024;12:89–102. doi:10.1016/j.cj.2024.01.003. [17] Han J, et al. Genome-wide association study of maize drought tolerance using high-density SNP markers. Theor Appl Genet. 2023;136:45. doi:10.1007/s00122-023-04245-6. [18] Ding X, et al. Genetic diversity and population structure of maize landraces from Southwest China using SSR markers. Crop Sci. 2021;61:1234–1245. doi:10.1002/csc2.20412. [19] Rahman M, et al. Genetic variability and heritability of agronomic traits in maize under drought stress. Euphytica. 2023;219:34. doi:10.1007/s10681-023-03134-5. [20] Ogunniyi O, et al. Drought stress effects on maize yield and quality in sub-Saharan Africa. Agric Syst. 2022;198:103387. doi:10.1016/j.agsy.2022.103387. [21] Huang Y, et al. Phenotypic and genotypic evaluation of maize inbred lines under water-limited conditions. Field Crops Res. 2021;260:108005. doi:10.1016/j.fcr.2020.108005. [22] Chen X, et al. Drought stress responses in maize: Insights from transcriptomic and proteomic analyses. Plant Physiol Biochem. 2023;196:145–156. doi:10.1016/j.plaphy.2023.02.015. [23] Yang H, et al. Drought stress impacts on maize root architecture and its genetic control. Plant Soil. 2021;465:123–135. doi:10.1007/s11104-021-04912-3. [24] Zhou Y, et al. Machine learning approaches for predicting drought tolerance in maize. Comput Electron Agric. 2024;217:108645. doi:10.1016/j.compag.2024.108645. [25] Peng Y, et al. QTL mapping for drought tolerance in maize using high-throughput phenotyping. BMC Genomics. 2021;22:456. doi:10.1186/s12864-021-07745-6. [26] Sun Y, et al. Physiological and genetic responses of maize to combined drought and heat stress. J Exp Bot. 2022;73:2345–2360. doi:10.1093/jxb/erac112. [27] Zhang Q, et al. Integrating genomic and phenotypic data for maize drought tolerance breeding. Plant Biotechnol J. 2023;21:678– 690. doi:10.1111/pbi.14012. [28] Tang L, et al. Genomic selection for drought tolerance in maize: Current status and future prospects. Plant Breed Rev. 2021;45:123–145. doi:10.1002/9781119716924.ch4.