Tolerant Maize Research Articles

The ZmbHLH47-ZmSnRK2.9 Module Promotes Drought Tolerance in Maize.

Drought stress globally poses a significant threat to maize (Zea mays L.) productivity and the underlying molecular mechanisms of drought tolerance remain elusive. In this study, we characterized ZmbHLH47, a basic helix-loop-helix (bHLH) transcription factor, as a positive regulator of drought tolerance in maize. ZmbHLH47 expression was notably induced by both drought stress and abscisic acid (ABA). Transgenic plants overexpressing ZmbHLH47 displayed elevated drought tolerance and ABA responsiveness, while the zmbhlh47 mutant exhibited increased drought sensitivity and reduced ABA sensitivity. Mechanistically, it was revealed that ZmbHLH47 could directly bind to the promoter of ZmSnRK2.9 gene, a member of the subgroup III SnRK2 kinases, activating its expression. Furthermore, ZmSnRK2.9-overexpressing plants exhibited enhanced ABA sensitivity and drought tolerance, whereas the zmsnrk2.9 mutant displayed a decreased sensitivity to both. Notably, overexpressing ZmbHLH47 in the zmsnrk2.9 mutant closely resembled the zmsnrk2.9 mutant, indicating the importance of the ZmbHLH47-ZmSnRK2.9 module in ABA response and drought tolerance. These findings provided valuable insights and a potential genetic resource for enhancing the environmental adaptability of maize.

ZmASR1 negatively regulates drought stress tolerance in maize

Abscisic acid-, stress-, and ripening-induced (ASR) proteins in plants play a significant role in plant response to diverse abiotic stresses. However, the functions of ASR genes in maize remain unclear. In the present study, we identified a novel drought-induced ASR gene in maize (ZmASR1) and functionally characterized its role in mediating drought tolerance. The transcription of ZmASR1 was upregulated under drought stress and abscisic acid (ABA) treatment, and the ZmASR1 protein was observed to exhibit nuclear and cytoplasmic localization. Moreover, ZmASR1 knockout lines generated with the CRISPR–Cas9 system showed lower ROS accumulation, higher ABA content, and a higher degree of stomatal closure than wild-type plants, leading to higher drought tolerance. Transcriptome sequencing data indicated that the significantly differentially expressed genes in the drought treatment group were mainly enriched in ABA signal transduction, antioxidant defense, and photosynthetic pathway. Taken together, the findings suggest that ZmASR1 negatively regulates drought tolerance and represents a candidate gene for genetic manipulation of drought resistance in maize.

Identification and characterization of ACR gene family in maize for salt stress tolerance.

Members of the ACR gene family are commonly involved in various physiological processes, including amino acid metabolism and stress responses. In recent decades, significant progress has been made in the study of ACR genes in plants. However, little is known about their characteristics and function in maize. In this study, ACR genes were identified from the maize genome, and their molecular characteristics, gene structure, gene evolution, gene collinearity analysis, cis-acting elements were analyzed. qRT-PCR technology was used to verify the expression patterns of the ZmACR gene family in different tissues under salt stress. In addition, Ectopic expression technique of ZmACR5 in Arabidopsis thaliana was utilized to identify its role in response to salt stress. A total of 28 ZmACR genes were identified, and their molecular characteristics were extensively described. Two gene pairs arising from segmented replication events were detected in maize, and 18 collinear gene pairs were detected between maize and 3 other species. Through phylogenetic analysis, three subgroups were revealed, demonstrating distinct divergence between monocotyledonous and dicotyledonous plants. Analysis of ZmACR cis-acting elements revealed the optional involvement of ZmACR genes in light response, hormone response and stress resistance. Expression analysis of 8 ZmACR genes under salt treatment clearly revealed their role in the response to salt stress. Ectopic overexpression of ZmACR5 in Arabidopsis notably reduced salt tolerance compared to that of the wild type under salt treatment, suggesting that ZmACR5 has a negative role in the response to salt stress. Taken together, these findings confirmed the involvement of ZmACR genes in regulating salt stress and contributed significantly to our understanding of the molecular function of ACR genes in maize, facilitating further research in this field.

Comparison of Juvenile Development of Maize and Sorghum in Six Temperate Soil Types under Extreme Water Regimes

Climate change requires the introduction of alternative crops in certain temperate areas due to the warmer and drier growing seasons. Maize, one of the most important crops, is projected to become less tolerant of a drier climate. Therefore, it is necessary to find an alternative species that is less susceptible to environmental stressors. This study compared the germination, growth vigour, and stress tolerance of maize and sorghum grow in six types of soil under three water regimes. The results indicate that sorghum germination is faster and more uniform. The most significant differences in germination rates were found in chernozem (88.9% and 72.2% for sorghum and maize, respectively) and saline solonetz (74.4% and 63.3% for sorghum and maize, respectively). Maize exhibited higher growth vigour only in three cases, i.e., under solonetz–flooding, shifting sand–drought, and brown forest floor–flooding conditions. An ANOVA showed a significant difference between sorghum and maize stress conditions due to soil conditions and water availability (p < 0.0001). Sorghum can be a suitable alternative to maize, but only in areas with hot, dry periods and in areas where the soil is not too prone to waterlogging, regardless of its quality.

Exploring the Impact of Phosphorus Application on Boron Toxicity Tolerance in Maize and Sunflower Under Aerobic Conditions, and Rice Under Anaerobic Conditions

ABSTRACT Both phosphorus (P) and boron (B) can interact with each other due to their similar properties and P can hinder the uptake of boron by plants. In this study, the effect of P and B concentrations on the growth of rice, sunflower, and maize plants grown under greenhouse conditions in an environment that would induce boron toxicity was investigated. To create a toxic environment, 40 mg kg−1 B was applied to rice plants, and 30 and 25 mg kg−1 B were applied to sunflower and maize plants, respectively. To alleviate the toxicity, 500 mg kg−1 P was added to the respective pots. The results of the study showed that B application reduced the fresh and dry weight of all plant species, while significant increases were observed with the addition of P. Among the applied P sources, TSP was found to be more effective than H3PO4 in terms of fresh and dry weight of maize plants. Plant-B concentrations increased with B application but were significantly reduced by the applied P sources, with no difference observed among the P sources. Plant-P concentrations, which decreased with B applications, increased as a result of P applications. In particular, H3PO4 was found to be more effective than TSP in terms of plant-P concentration, especially in sunflower and maize plants. This study determined that P fertilization can be beneficial in reducing the damage caused by boron toxicity, which is a stress factor that severely limits agricultural production in regions with arid and semi-arid climates.

Autophagy receptor ZmNBR1 promotes the autophagic degradation of ZmBRI1a and enhances drought tolerance in maize.

Drought stress is a crucial environmental factor that limits plant growth, development, and productivity. Autophagy of misfolded proteins can help alleviate the damage caused in plants experiencing drought. However, the mechanism of autophagy-mediated drought tolerance in plants remains largely unknown. Here, we cloned the gene for a maize (Zea mays) selective autophagy receptor, NEXT TO BRCA1 GENE 1 (ZmNBR1), and identified its role in the response to drought stress. We observed that drought stress increased the accumulation of autophagosomes. RNA sequencing and reverse transcription-quantitative polymerase chain reaction showed that ZmNBR1 is markedly induced by drought stress. ZmNBR1 overexpression enhanced drought tolerance, while its knockdown reduced drought tolerance in maize. Our results established that ZmNBR1 mediates the increase in autophagosomes and autophagic activity under drought stress. ZmNBR1 also affects the expression of genes related to autophagy under drought stress. Moreover, we determined that BRASSINOSTEROID INSENSITIVE 1A (ZmBRI1a), a brassinosteroid receptor of the BRI1-like family, interacts with ZmNBR1. Phenotype analysis showed that ZmBRI1a negatively regulates drought tolerance in maize, and genetic analysis indicated that ZmNBR1 acts upstream of ZmBRI1a in regulating drought tolerance. Furthermore, ZmNBR1 facilitates the autophagic degradation of ZmBRI1a under drought stress. Taken together, our results reveal that ZmNBR1 regulates the expression of autophagy-related genes, thereby increasing autophagic activity and promoting the autophagic degradation of ZmBRI1a under drought stress, thus enhancing drought tolerance in maize. These findings provide new insights into the autophagy degradation of brassinosteroid signaling components by the autophagy receptor NBR1 under drought stress.

Meta-Quantitative Trait Loci Analysis and Candidate Gene Mining for Drought Tolerance-Associated Traits in Maize (Zea mays L.).

Drought is one of the major abiotic stresses with a severe negative impact on maize production globally. Understanding the genetic architecture of drought tolerance in maize is a crucial step towards the breeding of drought-tolerant varieties and a targeted exploitation of genetic resources. In this study, 511 quantitative trait loci (QTL) related to grain yield components, flowering time, and plant morphology under drought conditions, as well as drought tolerance index were collected from 27 published studies and then projected on the IBM2 2008 Neighbors reference map for meta-analysis. In total, 83 meta-QTL (MQTL) associated with drought tolerance in maize were identified, of which 20 were determined as core MQTL. The average confidence interval of MQTL was strongly reduced compared to that of the previously published QTL. Nearly half of the MQTL were confirmed by co-localized marker-trait associations from genome-wide association studies. Based on the alignment of rice proteins related to drought tolerance, 63 orthologous genes were identified near the maize MQTL. Furthermore, 583 candidate genes were identified within the 20 core MQTL regions and maize-rice homologous genes. Based on KEGG analysis of candidate genes, plant hormone signaling pathways were found to be significantly enriched. The signaling pathways can have direct or indirect effects on drought tolerance and also interact with other pathways. In conclusion, this study provides novel insights into the genetic and molecular mechanisms of drought tolerance in maize towards a more targeted improvement of this important trait in breeding.

Soybean steroids improve crop abiotic stress tolerance and increase yield.

Sterols have long been associated with diverse fields, such as cancer treatment, drug development, and plant growth; however, their underlying mechanisms and functions remain enigmatic. Here, we unveil a critical role played by a GmNF-YC9-mediated CCAAT-box transcription complex in modulating the steroid metabolism pathway within soybeans. Specifically, this complex directly activates squalene monooxygenase (GmSQE1), which is a rate-limiting enzyme in steroid synthesis. Our findings demonstrate that overexpression of either GmNF-YC9 or GmSQE1 significantly enhances soybean stress tolerance, while the inhibition of SQE weakens this tolerance. Field experiments conducted over two seasons further reveal increased yields per plant in both GmNF-YC9 and GmSQE1 overexpressing plants under drought stress conditions. This enhanced stress tolerance is attributed to the reduction of abiotic stress-induced cell oxidative damage. Transcriptome and metabolome analyses shed light on the upregulation of multiple sterol compounds, including fucosterol and soyasaponin II, in GmNF-YC9 and GmSQE1 overexpressing soybean plants under stress conditions. Intriguingly, the application of soybean steroids, including fucosterol and soyasaponin II, significantly improves drought tolerance in soybean, wheat, foxtail millet, and maize. These findings underscore the pivotal role of soybean steroids in countering oxidative stress in plants and offer a new research strategy for enhancing crop stress tolerance and quality from gene regulation to chemical intervention.

Aquaporin ZmTIP2;3 Promotes Drought Resistance of Maize through Symbiosis with Arbuscular Mycorrhizal Fungi.

Arbuscular mycorrhizal fungi symbiosis plays important roles in enhancing plant tolerance to biotic and abiotic stresses. Aquaporins have also been linked to improved drought tolerance in plants and the regulation of water transport. However, the mechanisms that underlie this association remain to be further explored. In this study, we found that arbuscular mycorrhiza fungi symbiosis could induce the gene expression of the aquaporin ZmTIP2;3 in maize roots. Moreover, compared with the wild-type plants, the maize zmtip2;3 mutant also showed a lower total biomass, colonization rate, relative water content, and POD and SOD activities after arbuscular mycorrhiza fungi symbiosis under drought stress. qRT-PCR assays revealed reduced expression levels of stress genes including LEA3, P5CS4, and NECD1 in the maize zmtip2;3 mutant. Taken together, these data suggest that ZmTIP2;3 plays an important role in promoting maize tolerance to drought stress during arbuscular mycorrhiza fungi symbiosis.

Microbacterium azadirachtae CNUC13 Enhances Salt Tolerance in Maize by Modulating Osmotic and Oxidative Stress.

Soil salinization is one of the leading threats to global ecosystems, food security, and crop production. Plant growth-promoting rhizobacteria (PGPRs) are potential bioinoculants that offer an alternative eco-friendly agricultural approach to enhance crop productivity from salt-deteriorating lands. The current work presents bacterial strain CNUC13 from maize rhizosphere soil that exerted several PGPR traits and abiotic stress tolerance. The strain tolerated up to 1000 mM NaCl and 30% polyethylene glycol (PEG) 6000 and showed plant growth-promoting (PGP) traits, including the production of indole-3-acetic acid (IAA) and siderophore as well as phosphate solubilization. Phylogenetic analysis revealed that strain CNUC13 was Microbacterium azadirachtae. Maize plants exposed to high salinity exhibited osmotic and oxidative stresses, inhibition of seed germination, plant growth, and reduction in photosynthetic pigments. However, maize seedlings inoculated with strain CNUC13 resulted in significantly improved germination rates and seedling growth under the salt-stressed condition. Specifically, compared with the untreated control group, CNUC13-treated seedlings exhibited increased biomass, including fresh weight and root system proliferation. CNUC13 treatment also enhanced photosynthetic pigments (chlorophyll and carotenoids), reduced the accumulation of osmotic (proline) and oxidative (hydrogen peroxide and malondialdehyde) stress indicators, and positively influenced the activities of antioxidant enzymes (catalase, superoxide dismutase, and peroxidase). As a result, CNUC13 treatment alleviated oxidative stress and promoted salt tolerance in maize. Overall, this study demonstrates that M. azadirachtae CNUC13 significantly enhances the growth of salt-stressed maize seedlings by improving photosynthetic efficiency, osmotic regulators, oxidative stress resilience, and antioxidant enzyme activity. These findings emphasize the potential of utilizing M. azadirachtae CNUC13 as a bioinoculant to enhance salt stress tolerance in maize, providing an environmentally friendly approach to mitigate the negative effects of salinity and promote sustainable agriculture.

Genetic variations in ZmEREB179 are associated with waterlogging tolerance in maize

Maize (Zea mays) is highly susceptible to waterlogging stress, which reduces both the yield and quality of this important crop. However, the molecular mechanism governing waterlogging tolerance is poorly understood. In this study, we identify a waterlogging- and ethylene-inducible gene ZmEREB179 that encodes an ethylene responsive factor (ERF) localized in the nucleus. Overexpression of ZmEREB179 in maize increases the sensitivity to waterlogging stress. Conversely, the zmereb179 knockout mutants are more tolerant to waterlogging, suggesting that ZmEREB179 functions as a negative regulator of waterlogging tolerance. A transcriptome analysis of the ZmEREB179-overexpressing plants reveals that the ERF-type transcription factor modulates the expression of various stress-related genes, including ZmEREB180. We find that ZmEREB179 directly targets the ZmEREB180 promoter and represses its expression. Notably, the analysis of a panel of 220 maize inbred lines reveals that genetic variations in the ZmEREB179 promoter (Hap2) are significantly associated with waterlogging resistance. The functional association of Hap2 with waterlogging resistance is tightly co-segregated into two F2 segregating populations, highlighting its potential applications in breeding programs. Our findings shed light on the involvement of the transcriptional cascade of ERFs in regulating plant-waterlogging tolerance.

Genome-wide identification and evolutionary analysis of the AP2/EREBP, COX and LTP genes in Zea mays L. under drought stress

AP2 (APETALA2)/EREBP (ethylene-responsive element-binding protein), cytochrome c oxidase (COX) and nonspecific lipid transfer proteins (LTP) play important roles in the response to drought stress. This is the first study to identify the COX gene in Zea mays L. via genome-wide analysis. The qRT‒PCR results indicated that AP2/EREBP, COX and LTP were downregulated, with fold changes of 0.84, 0.53 and 0.31, respectively, after 12 h of drought stress. Genome-wide analysis identified 78 AP2/EREBP, 6 COX and 10 LTP genes in Z. mays L. Domain analysis confirmed the presence of the AP2 domain, Cyt_c_Oxidase_Vb domain and nsLTP1 in the AP2/EREBP, COX and LTP proteins, respectively. The AP2/EREBP protein family (AP2) includes five different domain types: the AP2/ERF domain, the EREBP-like factor (EREBP), the ethylene responsive factor (ERF), the dehydration responsive element binding protein (DREB) and the SHN SHINE. Synteny analysis of the AP2/EREBP, COX and LTP genes revealed collinearity orthologous relationships in O. sativa, H. vulgare and A. thaliana. AP2/EREBP genes were found on the 10 chromosomes of Z. mays L. COX genes were found on chromosomes 1, 3, 4, 5, 7 and 8. LTP genes were found on chromosomes 1, 3, 6, 8, 9 and 10. In the present study, the Ka/Ks ratios of the AP2/EREBP paralogous pairs indicated that the AP2/EREBP genes were influenced primarily by purifying selection, which indicated that the AP2/EREBP genes received strong environmental pressure during evolution. The Ka/Ks ratios of the COX-3/COX-4 paralogous pairs indicate that the COX-3/COX-4 genes were influenced primarily by Darwinian selection (driving change). For the LTP genes, the Ka/Ks ratios of the LTP-1/LTP-10, LTP-5/LTP-3 and LTP-4/LTP-8 paralogous pairs indicate that these genes were influenced primarily by purifying selection, while the Ka/Ks ratios of the LTP-2/LTP-6 paralogous pairs indicate that these genes were influenced primarily by Darwinian selection. The duplication time of the AP2/EREBP paralogous gene pairs in Z. mays L. ranged from approximately 9.364 to 100.935 Mya. The duplication time of the COX-3/COX-4 paralogous gene pair was approximately 5.217 Mya. The duplication time of the LTP paralogous gene pairs ranged from approximately 19.064 to 96.477 Mya. The major focus of research is to identify the genes that are responsible for drought stress tolerance to improve maize for drought stress tolerance. The results of the present study will improve the understanding of the functions of the AP2/EREBP, COX and LTP genes in response to drought stress.

Factors Influencing Farmers’ Attitude to Adopt Drought Tolerant Maize Varieties in Ondo State, Nigeria

The study investigated factors influencing farmers’ attitude towards adoption of drought-tolerant maize varieties. One hundred maize farmers were selected using a multi-stage sampling procedure and data were collected through structured questionnaires. Information was collected on the socio-economic characteristics of the maize farmers, farmers’ level of awareness of drought-tolerant maize varieties, farmers’ attitudes towards agricultural innovation, constraints to adoption of drought-tolerant maize varieties and, factors influencing farmers’ attitude towards adoption of drought-tolerant maize varieties. Data were analyzed using frequencies, percentages, Pearson Product Moment Correlation and Logit regression. The findings revealed that 76% of the maize farmers had limited awareness regarding the benefits and characteristics of drought-tolerant maize varieties. Also, the majority (74%) of the farmers lacked knowledge about the quality and advantages of these varieties. Despite positive attitude (mean = 4.28) which was measured at ordinal level, several constraints to adoption were identified, mainly low output of drought tolerant maize varieties (mean = 2.30). The findings also showed the substantial impact of two key factors (that is, sex and income) as factors influencing farmers’ attitude to adopt drought-tolerant maize varieties. Farmers are yet to take advantage of drought-tolerant maize varieties as a mitigating strategy against climate change. The need for extension services and non-governmental organizations to step up awareness creation and training on best agronomic practices in growing the maize varieties is recommended.

Physiological and biochemical effects of 24-Epibrassinolide on drought stress adaptation in maize (Zea mays L.).

Maize production and productivity are affected by drought stress in tropical and subtropical ecologies, as the majority of the area under maize cultivation in these ecologies is rain-fed. The present investigation was conducted to study the physiological and biochemical effects of 24-Epibrassinolide (EBR) as a plant hormone on drought tolerance in maize. Two maize hybrids, Vivek hybrid 9 and Bio 9637, were grown under three different conditions: (i) irrigated, (ii) drought, and (iii) drought+EBR. A total of 2 weeks before the anthesis, irrigation was discontinued to produce a drought-like condition. In the drought+EBR treatment group, irrigation was also stopped, and in addition, EBR was applied as a foliar spray on the same day in the drought plots. It was observed that drought had a major influence on the photosynthesis rate, membrane stability index, leaf area index, relative water content, and leaf water potential; this effect was more pronounced in Bio 9637. Conversely, the activities of antioxidant enzymes such as catalase (CAT), ascorbate peroxidase (APX), and superoxide dismutase (SOD) increased in both hybrids under drought conditions. Specifically, Vivek hybrid 9 showed 74% higher CAT activity under drought conditions as compared to the control. Additionally, EBR application further enhanced the activity of this enzyme by 23% compared to plants under drought conditions. Both hybrids experienced a significant reduction in plant girth due to drought stress. However, it was found that exogenously applying EBR reduced the detrimental effects of drought stress on the plant, and this effect was more pronounced in Bio 9637. In fact, Bio 9637 treated with EBR showed an 86% increase in proline content and a 70% increase in glycine betaine content compared to untreated plants under drought conditions. Taken together, our results suggested EBR enhanced tolerance to drought in maize hybrids. Hence, pre-anthesis foliar application of EBR might partly overcome the adverse effects of flowering stage drought in maize.

Improved yield by optimizing carbon, nitrogen metabolism and hormone balance in apical kernels under low nitrogen conditions using the low nitrogen–tolerant maize variety

ContextUsing low nitrogen (N)–tolerant maize varieties serves as a viable means to curtail N fertilizer application while improving crop yield. ObjectiveTo investigate the differences in carbon and nitrogen metabolic processes, and the hormones within kernels located at varying positions along the ear, between low N–tolerant and low N–sensitive maize varieties. Furthermore, this research aims to elucidate the ramifications of these observed disparities on kernel weight and yield, particularly when cultivated under low N conditions. MethodsThe low N–tolerant maize variety (ZH311) and low N–sensitive maize variety (XY508) were applied. The in–situ filed experiment with three N fertilizer treatments of 0 N (0 kg·N ha−1), 150 N (150 kg·N ha−1) and 300 N (300 kg·N ha−1) was conducted in 2017–2019. ResultsThe apical kernel weight of ZH311 was less affected by low N (0 N and 150 N) and the yield was 25.3–22.9% higher than XY508. The kernel weight was significantly and positively correlated with kernel starch and protein content. The starch and protein contents of ZH311 apical kernels were 6.3–7.3% and 12.4–14.4%, higher than XY508 under low N. It was indicated that the main factor affecting starch accumulation in the apical kernels was Susy activity and protein accumulation was IAA/GA3, Z+ZR/GA3 and GOGAT activity by the redundancy analysis. Under low N, the Susy and GOGAT activity, IAA/GA3 and Z+ZR/GA3 in the apical kernel of ZH311 were higher than XY508 by 51.4–39.3% and 65.4–46.9%, 62.1–33.1% and 41.8–48.2%. ConclusionsWe have demonstrated to improve the maize yield by increasing the apical kernel weight, which resulted in enhancing the uniformity of the kernel weight along the ear. Under low N conditions, the low N–tolerant maize variety was shown to facilitate the starch and protein biosynthesis by increasing the activity of key enzymes in the carbon and the nitrogen metabolism processes such as Susy and GOGAT in the apical kernels, and optimizing the hormone balance between IAA/GA3 and Z+ZR/GA3, to increase the kernel weight and yield. ImplicationsThe findings of this investigation will help understand the underlying factors contributing to the yield variations exhibited among distinct low N–tolerant maize varieties when cultivated under conditions of limited N availability. These insights could serve as the theoretical basis for breeding of low N–tolerant maize varieties and practical guidance for the formulation of N fertilizer management strategies.

Modeling performances of maize cultivars under current and future climate scenarios in southern central Ethiopian rift valley

BackgroundIn southern central rift valley of Ethiopia, maize is an important crop because of its adaptation to wider agro-ecologies and higher yield potential. However, most cultivars were not parameterized to include in the database of Decision Support System for Agro-technology Transfer (DSSAT). As a result simulation of growth and yield of those cultivars was not possible under changing climate.MethodsTwo set of independent crop, management and soil data were used for calibration and validation of genetic coefficients of maize cultivars (BH-540, BH-546, BH-547, Shala and Shone) under condition of historic weather (1990–2020). Later, we simulated the growth and yield of maize using twenty multimodel climate ensembles across RCP 4.5 and 8.5 during early, medium and late century across Shamana, Bilate, Hawassa and Dilla clusters using DSSATv4.8 model.ResultsCultivars BH-540, BH-546, BH-547, Shala and Shone produced yields of 5.7, 5.4, 5.2, 6.9 and 7.4 t ha−1 with the corresponding error percentage of − 0.1, − 0.8, − 1.0, − 6.1 and 2.6%. The results of normalized root mean square were 1.14–4.2 and 3.0–3.9%, for grain yield during calibration and validation, respectively showing an excellent rating. The simulation experiment produced 5.4–9.2 t ha−1 for grain yield of maize cultivars across the study areas, which is likely to fall close to 63.3% by 2070 if right adaptation options are not introduced necessitating switch in cultivars and production areas.ConclusionsThere is critical need for reduction of GHGs emissions, generation of innovative adaptation strategies, and development of drought and heat stress tolerant maize cultivars. Hence, researchers and policy makers shall act with utmost urgency to embark with breeding programs that target climate change adaptation traits in maize crop.

Integrated physiological, biochemical and transcriptomic analyses reveal the mechanism of salt tolerance induced by a halotolerant Serratia sp. NTN6 in maize

Salt stress is a serious environmental challenge that hinders crop growth and yield. Plant growth-promoting rhizobacteria (PGPR) can successfully and environmentally friendly boost plant development in saline soils. In this study, a halotolerant Serratia sp. NTN6 was isolated from the rhizosphere soil of halophyte Puccinellia tenuiflora and its plant growth-promoting properties were determined. NTN6 inoculation significantly promoted seed germination and seedling growth in maize under salt stress. Shoot height, stem thickness, root fresh weight, shoot fresh weight, root dry weight, and shoot dry weight of salt-stressed seedlings increased by 36.3%, 32.5%, 146.4%, 193.6%, 25.0%, and 109.6%, respectively, after inoculation with NTN6. NTN6-mediated maize salt tolerance was revealed via transcriptomic, physiological, and biochemical analyses. Under salt stress, NTN6 regulated the transcript levels of genes related to chlorophyll synthesis, photosynthesis apparatus, and carbon assimilation pathways, and thus increasing chlorophyll content, Fv/Fm, and net photosynthetic rate; NTN6 reduced the content of O2•–, H2O2, and MDA by regulating the transcripts and activities of antioxidant enzymes; NTN6 affected the transcriptional response of genes involved in ABA synthesis and signaling to salt stress and reduced ABA level. Finally, NTN6 boosted photosynthetic capacity in salt-stressed maize by modulating photochemical activity, C4 pathway and Calvin cycle as well as mitigating reactive oxygen species damage to the photosystem reaction center. This study first investigated the mechanism of Serratia sp.-induced salt tolerance in maize and these findings demonstrate the valuable contribution of halotolerant PGPR strain from halophytes in improving salinity tolerance in non-halophytic crops.

Metabolism of the 4-Hydroxyphenylpyruvate Dioxygenase Inhibitor, Mesotrione, in Multiple-Herbicide-Resistant Palmer amaranth (Amaranthus palmeri).

Metabolic resistance to the maize-selective, HPPD-inhibiting herbicide, mesotrione, occurs via Phase I ring hydroxylation in resistant waterhemp and Palmer amaranth; however, mesotrione detoxification pathways post-Phase I are unknown. This research aims to (1) evaluate Palmer amaranth populations for mesotrione resistance via survivorship, foliar injury, and aboveground biomass, (2) determine mesotrione metabolism rates in Palmer amaranth populations during a time course, and (3) identify mesotrione metabolites including and beyond Phase I oxidation. The Palmer amaranth populations, SYNR1 and SYNR2, exhibited higher survival rates (100%), aboveground biomass (c.a. 50%), and lower injury (25-30%) following mesotrione treatment than other populations studied. These two populations also metabolized mesotrione 2-fold faster than sensitive populations, PPI1 and PPI2, and rapidly formed 4-OH-mesotrione. Additionally, SYNR1 and SYNR2 formed 5-OH-mesotrione, which is not produced in high abundance in waterhemp or naturally tolerant maize. Metabolite features derived from 4/5-OH-mesotrione and potential Phase II mesotrione-conjugates were detected and characterized by liquid chromatography-mass spectrometry (LCMS).

Heat-Resistant Inbred Lines Coordinate the Heat Response Gene Expression Remarkably in Maize (Zea mays L.).

High temperatures are increasingly becoming a prominent environmental factor accelerating the adverse influence on the growth and development of maize (Zea mays L.). Therefore, it is critical to identify the key genes and pathways related to heat stress (HS) tolerance in maize. Great challenges have been faced in dissecting genetic mechanisms and uncovering master genes for HS tolerance. Here, Z58D showed more thermotolerance than AF171 at the seedling stage with a lower wilted leaf rate and H2O2 accumulation under HS conditions. Transcriptomic analysis identified 3006 differentially expressed genes (DEGs) in AF171 and 4273 DEGs in Z58D under HS treatments, respectively. Subsequently, GO enrichment analysis showed that commonly upregulated genes in AF171 and Z58D were significantly enriched in the following biological processes, including protein folding, response to heat, response to temperature stimulus and response to hydrogen peroxide. Moreover, the comparison between the two inbred lines under HS showed that response to heat and response to temperature stimulus were significantly over-represented for the 1234 upregulated genes in Z58D. Furthermore, more commonly upregulated genes exhibited higher expression levels in Z58D than AF171. In addition, maize inbred CIMBL55 was verified to be more tolerant than B73, and more commonly upregulated genes also showed higher expression levels in CIMBL55 than B73 under HS. These consistent results indicate that heat-resistant inbred lines may coordinate the remarkable expression of genes in order to recover from HS. Additionally, 35 DEGs were conserved among five inbred lines via comparative transcriptomic analysis. Most of them were more pronounced in Z58D than AF171 at the expression levels. These candidate genes may confer thermotolerance in maize.

The Synergistic Impact of Arbuscular Mycorrhizal Fungi and Compost Tea to Enhance Bacterial Community and Improve Crop Productivity under Saline-Sodic Condition.

Soil salinity has a negative impact on the biochemical properties of soil and on plant growth, particularly in arid and semi-arid regions. Using arbuscular mycorrhizal fungi (Glomus versiform) and foliar spray from compost tea as alleviating treatments, this study aimed to investigate the effects of alleviating salt stress on the growth and development of maize and wheat grown on a saline-sodic soil during the period of 2022/2023. Six treatments were used in the completely randomized factorial design experiment. The treatments included Arbuscular mycorrhizal fungus (AMF0, AMF1) and varied concentrations of compost tea (CT0, CT50, and CT100). AMF colonization, the bacterial community and endosphere in the rhizosphere, respiration rate, growth parameters, and the productivity were all evaluated. The application of AMF and CT, either separately or in combination, effectively mitigated the detrimental effects caused by soil salinity. The combination of AMF and CT proved to be highly efficient in improving the infection rate of AMF, the bacterial community in the rhizosphere and endosphere, growth parameters, and grain yield of maize and wheat. Therefore, it can be proposed that the inoculation of mycorrhizal fungi with compost tea in saline soils is an important strategy for enhancing salt tolerance in maize and wheat plants through improving microbial activity, the infection rate of AMF, and overall maize and wheat productivity.