Doubled haploid (DH) technology is widely used in crop breeding programs. Colchicine is the most frequently used chemical agent in the DH inducing. However, colchicine has disadvantage of high poisonousness. It is necessary to find some non-toxic or low toxic substitutes that should have the same effect as colchicine. In this study, two anti-microtubule herbicides, amiprophosmethyl (AMP) and Oryzalin, were used to double the haploids under different treatment conditions, and the doubling effects were compared with colchicine. The results showed that the highest doubling rate induced by APM is about 45% in the condition of 20 μM 24h. We calculated the actual doubling rate (survival rate × double rate), 38.23%, 20.64%, and 19.4% are the highest actual doubling rates induced by APM, colchicine, and oryzalin, respectively. Although both APM and Oryzalin can induce maize haploid doubling, comparing with the actual doubling rate, APM is better than colchicine. In addition, soaking seed had been proved the best way to operate and obtain the highest doubling haploids in all conditions. As a low toxic mitotic inducer, APM is a good substitute of colchicine in doubling maize haploids, which is suitable for application in the DH‐based breeding pipeline.

Low temperature during early spring severely impairs maize germination, leading to significant yield losses. To elucidate the mechanisms underlying cold tolerance at the germination stage, we compared two cold-tolerant maize inbred lines (AM and CM) with a cold-sensitive line (BM) under control (25 °C) and chilling (6 °C) conditions. Phenotypic observations showed that AM and CM maintained high germination rates and exhibited enhanced coleoptile elongation under cold stress, whereas BM displayed substantial growth inhibition. Cold-tolerant lines accumulated less malondialdehyde and showed markedly higher SOD and POD activities, indicating a stronger antioxidant defense. Transcriptome profiling revealed that cold tolerance is associated with a more robust transcriptional response in AM and CM, characterized by significant activation of the phenylpropanoid and flavonoid biosynthesis pathways. Among the differentially expressed genes, the class III peroxidase gene ZmPER5 was strongly upregulated in AM and CM but only weakly induced in BM, suggesting its central role in reinforcing the cell wall structure and enhancing ROS-scavenging capacity under chilling conditions. Other lignin- and flavonoid-related genes, including ZmHCT4 and ZmCYP75, also exhibited genotype-specific induction patterns consistent with cold tolerance. qRT-PCR validation confirmed the RNA-seq expression trends. These results demonstrate that maize cold tolerance during germination relies on the coordinated enhancement of antioxidant enzyme activity, activation of phenylpropanoid-derived lignin biosynthesis, and accumulation of protective flavonoids. The identified candidate genes, especially ZmPER5, provide valuable targets for improving cold tolerance in maize breeding.

Members of the WRKY transcription factors (TFs) family play crucial roles in biotic and abiotic stress responses in plants, but their roles in response to drought stress in maize (Zea mays L.) have not been fully elucidated. Maize ZmWRKY82, a group IIc WRKY gene, was isolated from maize using reverse transcription polymerase chain reaction (RT-PCR). Using the UniProt online database, we found that ZmWRKY82 encodes a 222-amino protein with conserved WRKYGKK and C-X₄-C-X₂₃-H-X₁-H motifs. ZmWRKY82 is strongly induced by polyethylene glycol (PEG), abscisic acid (ABA), methyl jasmonate (MeJA), salicylic acid (SA), and ethephon (ETH) treatments. The ZmWRKY82 protein was located in the cell nucleus. ZmWRKY82 had transcriptional activation capability and was able to bind to the W-box element. ZmWRKY82-overexpressing Arabidopsis and maize exhibited stronger drought resilience, which was associated with enhanced antioxidant enzyme activity and altered transcription level of drought-related genes. These findings suggest that ZmWRKY82 plays a central role in conferring drought tolerance in maize and may contribute to crop improvement and sustainable agricultural practices.

Background: Dirigent genes play crucial roles in regulating plant architecture development and responses to environmental stress. However, the pan-genomic attributes of these genes remain poorly characterized. Method: The dirigent pan-gene family was reconstructed using the public genome assemblies from the 26 maize Nested Association Mapping project founder lines. Orthogroup classification based on multiple sequence alignment revealed both core and variable family members. Evolutionary pressures were assessed through Ka/Ks ratio analysis, and promoter regions were examined for cis-acting regulatory elements. Haplotype, transcriptomic and genome-wide association study (GWAS) analyses were integrated to explore genetic diversity and functional relevance. Results: Most dirigent members were under purifying selection, whereas a subset may have undergone positive selection. Promoter analysis demonstrated enrichment of stress- and phytohormone-responsive cis-acting regulatory elements, suggesting that regulatory divergence was associated with environmental adaptation. Haplotype analysis revealed allelic diversity among heterotic clusters, potentially contributing to heterosis. Integration with public genome-wide association study datasets identified candidate genes significantly associated with plant architecture and kernel-quality-related traits. Transcriptome profiles indicated that several dirigent genes were preferentially expressed in the roots, suggesting their involvement in root development and nutrient uptake. In addition, public gene expression data showed that certain dirigent genes are induced in response to salt stress, supporting their putative roles in abiotic stress tolerance. Conclusions: These findings provide insights into the molecular mechanisms underlying dirigent gene functions and reveal candidate genes with potential utility for improving maize performance and stress resilience through molecular breeding.

Calmodulins (CaMs), which are important calcium-binding proteins, play critical roles in plant stress responses. However, limited information is available regarding the biological functions of CaMs under drought stress. In this study, we identified and isolated a CaM gene, ZmCaM2, from maize (Zea mays L.) in length and encodes a 184-amino acid protein containing four EF-hand domains capable of specifically binding calcium ions (Ca²⁺). Subcellular localization analysis revealed that ZmCaM2 is localized to the nucleus and membrane. Functional characterization indicated that ZmCaM2 negatively regulates drought tolerance in maize by increasing malondialdehyde (MDA) and reactive oxygen species (ROS) content while decreasing antioxidant enzyme activity, proline (Pro) content, abscisic acid (ABA) content and relative water content (RWC). Moreover, ZmCaM2 reduced maize sensitivity to ABA treatment, suggesting that ZmCaM2 negatively regulates the drought tolerance of maize by relying on the ABA pathway. These findings provide new insights into the functional role of ZmCaM2 and may facilitate the development of drought-resistant maize cultivars.

A reasonable method was used to analyze the effects of different substrates on the characters and yield of maize, and to improve the quality and yield of maize. The effects of the maize characters and yield of national Fluvo-aquic soil fertility and fertilizer efficiency monitoring base were analyzed from 6 aspects: fertilization and combined application, fertilization and density coupling, controlled release fertilizer (CRF), fertilization level, fertilization depth and proportion, and the amount of organic manure (chicken manure). Data processing is done by using Excel2003 and SPSS17.0 software, and multiple comparisons are made by using Duncan’s new multiple range test method. The experiment of the influence factor of fertilization and combined application shows that the combination of NPK+ organic fertilizer (constant and high) can increase maize character ratio and NPK+ high-amount organic manure can increase maize yield. The experiment of the influence factor of fertilization and density coupling shows that the maize characters reached the optimum under the condition of high fertilizer. The yield of maize is highest when the density is 60000 plants /hm2 and the amount of fertilizer is 10.71kg, 3.57kg and 8.93kg per 667m2. The experiment of the influence factor of controlled release fertilizer shows that the characters of CRF V and CRF VI are the best. The control time of CRF III, CRF V, CRF VI, and CRF IV compound fertilizer is long, which can increase maize yield. The experiment of the influence factor of fertilizer level shows that the best character of maize is achieved by using the controlled release fertilizer of Agricultural University 450 kg/hm2 and two-topdressing 600 kg/hm2. In the process of corn production, the use of A-40 treatment (Volfertile controlled release fertilizer 600kg/hm2) and the one-time application of base fertilizer can increase the yield of maize. The experiment of the influence factor of fertilization depth and proportion show that the best combination is that seed fertilizer 20% urea, 40% diammonium phosphate and potassium sulfate were applied under the surface of 8cm and base fertilizer 40% urea, 60% diammonium phosphate and potassium sulfate were applied under the surface of 16cm. It can improve the character and yield of maize at the same time. The experiment of the influence factor of organic manure (chicken manure) shows that the amount of organic fertilizer (chicken manure) 26923kg per hectare with fertilizing 35kg per plot is the best amount of fertilizer, and the yield of maize increases. The proposed method can comprehensively and accurately analyze the effects of different substrates on the character and yield of maize, which can promote rational fertilization in maize and improve the quality and yield of maize steadily.