Tolerant Sorghum Research Articles

Isolation and Bioinformatics Analysis of SK2-type of Dehydrin1 (DHN1) Gene from Egyptian Sorghum for Enhancing Salinity Stress Tolerance in Transgenic Rice

Isolation and Bioinformatics Analysis of SK2-type of Dehydrin1 (DHN1) Gene from Egyptian Sorghum for Enhancing Salinity Stress Tolerance in Transgenic Rice

Agronomic adaptations to heat stress: Sowing summer crops earlier

CONTEXTSummer crops are exposed to heat and drought stresses at critical stages during and after flowering, and their intensity and frequency are likely to increase with climate change. Agronomic stress avoidance offers the opportunity to temporally separate critical crop stages from heat and drought events. However, it might require sowing cold-sensitive summer crops earlier into colder than recommended soil temperatures. There is a need to understand how cold is too cold to sow summer crops early in late winter as well as what are the yield benefits and risks. OBJECTIVEHere, we quantify the likely benefits and trade-offs of sowing sorghum, a summer cereal, earlier to adapt to the increased frequency and intensity of heat and water stresses during flowering and grain filling. METHODSTwo years of multi-environment (n=32) genotype by management trials were conducted across the main sorghum growing regions of Australia. Environments (E) consisted of the combination of years, sites, three times of sowing (early, spring, and summer), and the use of supplementary irrigation. At each E a factorial combination of four plant populations (M) and eight commercial sorghum hybrids (G) were sown with three replications. Crop growth and yield components were measured, and the APSIM model was used to simulate all trials and treatments to quantify risks and derive insights into functional relationships between simulated and measured environmental covariates, and measured crop traits. RESULTSThe tested hybrids showed small differences in cold tolerance during crop establishment. Across the tested environments, the G×M combinations produced up to 60% variation in treatment yields across environment yields, which varied between <0.5 to about 10t ha-1; this translated into a ~5.5-fold variation in water use efficiency. Significant G×E and M×E interactions were observed for grain yield components. No G×M or G×E×M interactions were observed on yield or yield components. Early sowing was associated with a reduced risk of heat stress and water use transfer from vegetative to reproductive stages. Early sowing in late winter or early spring resulted in no significant yield gain or loss when all sites and years were included in the analysis. However, early sowing yielded between 1-2 t ha-1 more when the hottest sites and years were considered separately. This resulted from both the avoidance of heat stresses and milder or no terminal drought stresses. CONCLUSIONSEarly sowing of sorghum can reduce the likelihood of heat stresses around flowering as well as the likelihood of terminal drought stresses. Advantages include reduced yield losses in the hottest years and a transfer of water use to grain filling stages, resulting in increased grain yield and improved grain quality parameters. IMPLICATIONSEarly sowing, an agronomic adaptation, offers the opportunity to quickly adapt to the increase in the frequency and intensity of extreme hot events during critical crop stages. However, for the practice to be de-risked, there is a need to increase cold and chilling tolerance in sorghum and/or identify interventions that enhance seed germination and seedling vigour when the crop is sown early into cold soils.

Enumeration of Genetic Variability Parameters and Association among Early Seedling Growth Parameters under Polyethylene Glycol (PEG) induced Osmotic Stress in rabi Sorghum (Sorghum bicolor (l.) Moench)

Aims: The research aims to explore the variability within diverse rabi sorghum germplasms and identify the relationships among different early seedling growth traits. This will provide valuable insights for future breeding programs, aiding in the development of resilient sorghum varieties that can contribute to improved food security and agricultural sustainability. Study Design: The study was conducted by employing factorial complete randomized design (FCRD) with two replications. Where, two factors was considered, genotype as first factor and PEG concentration as second. Place and Duration of Study: The experiment was conducted during rabi season of 2023 at University of Agricultural Sciences Dharwad, Karnataka. Methodology: A total of 156 germplasm lines of rabi sorghum were assessed in vitro for early seedling growth characteristics, including germination percentage, shoot length, root length, seedling dry weight, and seedling vigor indices I and II, under both control and osmotic stress conditions induced by polyethylene glycol (PEG). Osmotic stress was induced by dissolving PEG 6000 in distilled water to achieve the desired concentration. The germplasm lines were then subjected to germination and early growth under these conditions using the paper towel method. The genetic variability parameters for each trait were quantified to examine the degree of variability in the material used, and correlation analysis was performed to understand the relationships among the traits studied. Results: The variance analysis showed highly significant differences among genotypes, treatments, and the genotype-by-environment (G×E) interactions. Genetic variability parameters revealed considerable variability across all traits studied, which tended to increase with higher stress levels. Moderate to high GCV and PCV was observed for all the traits studied. Correlation analysis demonstrated a strong, significant positive relationship among all seedling parameters, except between root length and shoot length, as well as between shoot length and germination percentage under control conditions. Conclusion: The study emphasizes the effect of osmotic stress on the early vigor and growth of sorghum seedlings. The findings reveal significant variability in seedling traits, suggesting that selection can be employed for genetic enhancement of these traits. Correlation analysis identified specific traits or combinations of traits that should be considered when selecting genotypes tolerant to osmotic stress conditions. These findings offer great potential to guide and improve selection and breeding programs focused on enhancing drought tolerant sorghum varieties.

An mRNA methylase and demethylase regulate sorghum salt tolerance by mediating N6-methyladenosine modification.

N 6-methyladenosine (m6A) modification is a crucial and widespread molecular mechanism governing plant development and stress tolerance. The specific impact of m6A regulation on plants with inherently high salt tolerance remains unclear. Existing research primarily focuses on the overexpression or knockout of individual writer or eraser components to alter m6A levels. However, a comprehensive study simultaneously altering overall m6A modification levels within the same experiment is lacking. Such an investigation is essential to determine whether opposing changes in m6A modification levels exert entirely different effects on plant salt tolerance. In this study, we identified the major writer member mRNA adenosine methylase A (SbMTA) in sorghum (Sorghum bicolor) as critical for sorghum survival. The sbmta mutant exhibits a phenotype characterized by reduced overall m6A, developmental arrest, and, ultimately, lethality. Overexpression of SbMTA increased m6A levels and salt tolerance, while overexpression of the m6A eraser alkylated DNA repair protein AlkB homolog 10B (SbALKBH10B) in sorghum showed the opposite phenotype. Comparative analyses between sorghum with different m6A levels reveal that SbMTA- and SbALKBH10B-mediated m6A alterations significantly impact the stability and expression levels of genes related to the ABA signaling pathway and growth under salt stress. In summary, this study unveils the intricate relationship between m6A modifications and salt tolerance in sorghum, providing valuable insights into how m6A modification levels on specific transcripts influence responses to salt stress.

Comprehensive analysis of ankyrin repeat gene family revealed SbANK56 confers drought tolerance in sorghum

Ankyrin repeat (ANK) proteins are crucial for cell growth, development, and response to hormones and environmental stress. However, there has been little research done to clarify the roles of ANK proteins in sorghum. In this study, 142 ANK genes of sorghum were identified and classified into 12 subfamilies according to the conserved domains. The cis-elements analysis revealed a substantial presence of stress-responsive elements within the promoter region of SbANK genes. After treated with drought, salt, and abscisic acid, SbANK56 showed the highest expression levels among family members by using quantitative real-time PCR (qRT-PCR) analysis. The survival rate was significantly improved by the overexpression of SbANK56 compared to wild type (WT) under drought conditions. SbANK56 overexpressing plants displayed lower malondialdehyde and higher proline contents compared to WT plants under drought conditions. Additionally, the expression levels of drought-associated genes were significantly increased in SbANK56 transgenic plants. Importantly, the analysis of natural variation in SbANK56 revealed a significant positive correlation between SbANK56Hap4 and both its differential expression and drought stress tolerance. Taken together, our results provide some evidence for improving drought tolerance in sorghum through breeding initiatives while also advancing our knowledge of the evolutionary trends and functional mechanisms underlying ANK genes.

Mitigation of salt stress in Sorghum bicolor L. by the halotolerant endophyte Pseudomonas stutzeri ISE12.

Increasing soil salinity, exacerbated by climate change, threatens seed germination and crop growth, causing significant agricultural losses. Using bioinoculants based on halotolerant plant growth-promoting endophytes (PGPEs) in modern agriculture is the most promising and sustainable method for supporting plant growth under salt-stress conditions. Our study evaluated the efficacy of Pseudomonas stutzeri ISE12, an endophyte derived from the extreme halophyte Salicornia europaea, in enhancing the salinity tolerance of sorghum (Sorghum bicolor L.). We hypothesized that P. stutzeri ISE12 would improve sorghum salt tolerance to salinity, with the extent of the increase in tolerance depending on the genotype's sensitivity to salt stress. Experiments were conducted for two sorghum genotypes differing in salinity tolerance (Pegah - salt tolerant, and Payam - salt sensitive), which were inoculated with a selected bacterium at different salinity concentrations (0, 100, 150, and 200 mM NaCl). For germination, we measured germination percentage and index, mean germination time, vigor, shoot and root length of seedlings, and fresh and dry weight. In pot experiments, we assessed the number of leaves, leaf area, specific leaf area, leaf weight ratio, relative root weight, plantlet shoot and root length, fresh and dry weight, proline and hydrogen peroxide concentrations, and peroxidase enzyme activity. Our study demonstrated that inoculation significantly enhanced germination and growth for both sorghum genotypes. The salinity-sensitive genotype (Payam) responded better to bacterial inoculation during germination and early seedling growth stages, showing approximately 1.4 to 1.8 times greater improvement than the salinity-tolerant genotype (Pegah). Payam also displayed better performance at the plantlet growth stage, between 1.1 and 2.6 times higher than Pegah. Furthermore, inoculation significantly reduced hydrogen peroxide, peroxidase activity, and proline levels in both sorghum genotypes. These reductions were notably more pronounced in Payam, with up to 1.5, 1.3, and 1.5 times greater reductions than in Pegah. These results highlight the efficacy of P. stutzeri ISE12 in alleviating oxidative stress and reducing energy expenditure on defense mechanisms in sorghum, particularly benefiting salt-sensitive genotypes. Our findings highlight the potential of the bacterial endophyte P. stutzeri ISE12 as a valuable bioinoculant to promote sorghum growth under saline conditions.

A coiled-coil domain mutation in the NLR receptor SbYR1 coordinates plant growth and stress tolerance in sorghum

A coiled-coil domain mutation in the NLR receptor SbYR1 coordinates plant growth and stress tolerance in sorghum

Integration of transcriptional responses in cold contrasting sorghum genotypes under low temperatures

AbstractSorghum is a crop that is susceptible to low temperatures. However, due to the extreme global temperatures, new genotypes have been bred to adapt better to cold climates. Therefore, to better understand the metabolic and molecular differences that may contribute to the improved cold tolerance of these genotypes, it is essential to investigate whether specific molecules play a key role in determining the degree of sorghum tolerance. Furthermore, identifying genes associated with cold tolerance may assist in the development of more robust and productive sorghum cultivars. Here, we analysed the changes in selected elements of the antioxidant metabolism, genes, and miRNAs in two sorghum varieties with different degrees of tolerance to cold stress at different times of exposure to cold stress. The high expression of SbCBF6 in response to cold treatment in early time in the tolerant variety suggests its involvement in the cold response, thereby facilitating a better adaptation of the plant to cold conditions. MiR398 and miR394 showed contrasting behaviour in both varieties in low temperatures, resulting in interesting miRNAs in the degree of sorghum tolerance. MiR319, a marker for the selection of cold‐tolerant cultivars, presents a decrease, suggesting that the better capacity to repress the expression of several members of TCP family of transcription factor genes might be involved in better tolerance to cold stress. This study shows the changes of molecules of interest in response to cold stress in sorghum, marking the difference between cold‐susceptible and cold‐tolerant sorghum plants, which can contribute to selecting tolerant genotypes, allowing new strategies to enhance crop productivity and food security, in regions where low temperatures significantly constrain crop growth and yield.

Comparative analyses suggest a link between mRNA splicing, stability, and RNA covalent modifications in flowering plants

BackgroundIn recent years, covalent modifications on RNA nucleotides have emerged as pivotal moieties influencing the structure, function, and regulatory processes of RNA Polymerase II transcripts such as mRNAs and lncRNAs. However, our understanding of their biological roles and whether these roles are conserved across eukaryotes remains limited.ResultsIn this study, we leveraged standard polyadenylation-enriched RNA-sequencing data to identify and characterize RNA modifications that introduce base-pairing errors into cDNA reads. Our investigation incorporated data from three Poaceae (Zea mays, Sorghum bicolor, and Setaria italica), as well as publicly available data from a range of stress and genetic contexts in Sorghum and Arabidopsis thaliana. We uncovered a strong enrichment of RNA covalent modifications (RCMs) deposited on a conserved core set of nuclear mRNAs involved in photosynthesis and translation across these species. However, the cohort of modified transcripts changed based on environmental context and developmental program, a pattern that was also conserved across flowering plants. We determined that RCMs can partly explain accession-level differences in drought tolerance in Sorghum, with stress-associated genes receiving a higher level of RCMs in a drought tolerant accession. To address function, we determined that RCMs are significantly enriched near exon junctions within coding regions, suggesting an association with splicing. Intriguingly, we found that these base-pair disrupting RCMs are associated with stable mRNAs, are highly correlated with protein abundance, and thus likely associated with facilitating translation.ConclusionsOur data point to a conserved role for RCMs in mRNA stability and translation across the flowering plant lineage.

Genome‐Wide Identification of CLE Gene Family and Function Analysis of SbCLE39 Under Salt Stress in Sorghum

ABSTRACTCLE proteins are a class of signalling factors involved in plant growth and abiotic stress response. They play crucial roles in processes such as cell differentiation, chlorophyll synthesis and abscisic acid (ABA) signal transduction. However, the function of the CLE genes in Sorghum bicolor remains unclear. In this study, 42 sorghum CLE genes were identified, and their evolutionary relationship, gene structure, amino acid sequence and homologous genes were analysed. We also examined the expression levels of CLE genes under various treatment conditions. Transcriptome data showed that there were significant differences in the expression patterns of 42 CLE genes in different tissues and organs. It is worth noting that SbCLE39 is mainly highly expressed in sorghum roots. At the same time, the expression of SbCLE39 decreased significantly under salt and ABA treatment. Compared with wild‐type yeast cells (EV), yeast cells with high expression of SbCLE39 had lower tolerance to salt stress. In addition, the excessive accumulation of ABA caused by external application of SbCLE39p reduced the salt tolerance of sorghum. These findings suggest that SbCLE39 negatively regulates the salt tolerance of sorghum. These results lay a foundation for revealing the mechanism of CLE genes regulating the salt tolerance of sorghum and are of great significance for the cultivation of salt‐tolerant crops.

Association between Reactive Oxygen Species, Transcription Factors, and Candidate Genes in Drought-Resistant Sorghum.

Drought stress is one of the most severe natural disasters in terms of its frequency, length, impact intensity, and associated losses, making it a significant threat to agricultural productivity. Sorghum (Sorghum bicolor), a C4 plant, shows a wide range of morphological, physiological, and biochemical adaptations in response to drought stress, paving the way for it to endure harsh environments. In arid environments, sorghum exhibits enhanced water uptake and reduced dissipation through its morphological activity, allowing it to withstand drought stress. Sorghum exhibits physiological and biochemical resistance to drought, primarily by adjusting its osmotic potential, scavenging reactive oxygen species, and changing the activities of its antioxidant enzymes. In addition, certain sorghum genes exhibit downregulation capabilities in response to drought stress. Therefore, in the current review, we explore drought tolerance in sorghum, encompassing its morphological characteristics and physiological mechanisms and the identification and selection of its functional genes. The use of modern biotechnological and molecular biological approaches to improving sorghum resistance is critical for selecting and breeding drought-tolerant sorghum varieties.

Agronomic adaptations to heat stress: sowing summer crops early in late winter.

Abstract CONTEXT: Summer crops are exposed to heat and drought stresses at critical stages during and after flowering, and their intensity and frequency are likely to increase with climate change. Agronomic stress avoidance offers the opportunity to temporally separate critical crop stages from heat and drought events, though it might require sowing cold sensitive summer crops early in late winter into colder than recommended soil temperatures. There is a need to understand how cold is too cold to sow summer crops early in late winter as well as what are the yield benefits and risks. OBJECTIVE: Here we quantify the likely benefits and trade-offs of sowing sorghum, a summer cereal, early in late winter as an adaptation to the increased frequency and intensity of heat and water stresses during flowering and grain filling. METHODS: Two seasons of multi-environment ( n =32) genotype by management trials were conducted across sub-tropical and semi-arid regions of eastern Australia. Environments (E) consisted of the combination of seasons, sites, three times of sowing (early, spring, and summer), and the use of supplementary irrigation. At each E a factorial combination of four plant populations (M) and eight commercial sorghum hybrids (G) were sown with three replications. Crop growth and yield components were measured, and the APSIM model was used to simulate all trials and treatments to quantify risks, and derive insights into functional relationships between simulated and measured environmental co-variates, and measured crop traits. RESULTS: The tested hybrids showed small differences in cold tolerance during crop establishment. Across the tested environments the G×M combinations produced up to 60% variation in treatment yields across environment yields, that varied between &lt;0.5 to about 10t ha -1 , this translated into a ~8-fold variation in water use efficiency. Significant G×E and M×E interactions were observed for grain yield components. No G×M or G×E×M interactions were observed on yield or yield components. Early sowing was associated to a reduced risk of heat stress, and water use transfer from vegetative to reproductive stages. Early sowing in late winter or early spring resulted in no significant yield gain or yield loss when all sites and seasons are included in the analysis, and between 1-2 t ha -1 yield gains when the hottest sites and seasons are considered separately. The likelihood and severity of terminal drought stresses was also reduced with late winter and early spring sowings, improving yield quality parameters. CONCLUSIONS: Early sowing of sorghum can reduce the likelihood of heat stresses around flowering as well as the likelihood of terminal drought stresses. Advantages include reduced yield losses in the hottest seasons, and a transfer of water use to grain filling stages that resulted in increased grain yield and improved grain quality parameters. IMPLICATIONS: Agronomic adaptations offer opportunity to quickly adapt to the increase in the frequency and intensity of extreme hot events during critical crop stages. However, for the practice to be de-risked there is need to increase cold and chilling tolerance in sorghum, and or identify interventions that enhance seed germination and seedling vigour when the crop is sown early into cold soils.

Effects of mycorrhizal symbiosis and Ulva lactuca seaweed extract on growth, carbon/nitrogen metabolism, and antioxidant response in cadmium-stressed sorghum plant.

In our study on the effect of cadmium (Cd) toxicity (200µM) on the growth of Sorghum bicolor (L.) Moench plants, cultivated with arbuscular mycorrhizal fungi (AMF) (Glomus intraradices) and/or under seaweed treatment (3% Ulva lactuca extract) (U. lactuca), we found that AMF increased the tolerance of sorghum to cadmium stress, either alone or in combination with the seaweed treatment. Morphological parameters were higher in these two culture conditions, with increased chlorophyll content. AMF reduced Cd accumulation in roots and inhibited its translocation to the aerial part, while seaweed treatment alone significantly increased Cd accumulation in leaves and roots without affecting plant growth compared to stressed witnesses. Treatment with AMF and/or U. lactuca attenuated oxidative stress, measured by activation of superoxide dismutase, and resulted in a significant decrease in malondialdehyde and superoxide ions (O2-) in treated plants. Furthermore, it induced significant alterations in carbon and nitrogen metabolic pathways, with a significant increase in the activity of enzymes such as glutamine synthetase, glutamate synthase (GOGAT), glutamate dehydrogenase, phosphoenolpyruvate carboxylase, aspartate aminotransferase and isocitrate dehydrogenase in the leaves of each treated plant. These results confirm that AMF, U. lactuca algae extract and their combination can improve the biochemical parameters of sorghum under Cd stress, through modification of the antioxidant response on one hand, and improved nitrogen absorption and assimilation efficiency on the other.

Applying unoccupied aerial systems to assess genetic gain from mass selection for tembotrione tolerance in sorghum (Sorghum bicolor)

AbstractThe post‐emergent herbicide options to control grasses in sorghum have historically been limited. Therefore, a mass selection program was implemented to increase the tolerance of sorghum to the broad‐spectrum herbicide tembotrione. The objectives of this study are to determine (i) which observation timing and vegetative indices are most effective in assessing sorghum injury to tembotrione using unoccupied aerial system imagery and (ii) if mass selection can be used to increase the tolerance of sorghum to tembotrione. Using an unoccupied aerial system, several vegetative indices, collected at either 14 or 21 days after tembotrione application, accurately measured sorghum injury. Over four cycles of selection, tembotrione tolerance increased in a linear and consistent manner. This demonstrates that mass selection can be used as a strategy for developing herbicide tolerance in crops. The modest, but steady genetic gain indicates both the quantitative nature of the trait and sufficient heritability to improve it. Given further development, tembotrione‐resistant sorghum hybrids could provide an effective means of post‐emergent weed control for a range of common weeds.

SbMYC2 mediates jasmonic acid signaling to improve drought tolerance via directly activating SbGR1 in sorghum.

SbMYC2 functions as a key regulator under JA signaling in enhancing drought tolerance of sorghum through direct activating SbGR1. Drought stress is one of the major threats to crop yield. In response to drought stress, functions of basic helix-loop-helix (bHLH) transcription factors (TFs) have been reported in Arabidopsis and rice, but little is known for sorghum. Here, we characterized the function of SbMYC2, a bHLH TF in sorghum, and found that SbMYC2 responded most significantly to PEG-simulated drought stress and JA treatments. Overexpression of SbMYC2 significantly enhanced drought tolerance in Arabidopsis, rice and sorghum. In addition, it reduced reactive oxygen species (ROS) accumulation and increased chlorophyll content in sorghum leaves. While silencing SbMYC2 by virus-induced gene silencing (VIGS) resulted in compromised drought tolerance of sorghum seedlings. Moreover, SbMYC2 can directly activate the expression of GLUTATHIONE-DISULFIDE REDUCTASE gene SbGR1. SbGR1 silencing led to significantly weakened drought tolerance of sorghum, and higher ROS accumulation and lower chlorophyll content in sorghum leaves were detected. In addition, SbMYC2 can interact with SbJAZs, suppressors of JA signaling, and thus can mediate JA signaling to activate SbGR1, thereby regulating sorghum's tolerance to drought stress. Overall, our findings demonstrate that bHLH TF SbMYC2 plays an important role in sorghum's response to drought stress, thus providing one theoretical basis for genetic enhancement of sorghum and even rice.

Macronutrient application rescues performance of tolerant sorghum genotypes when infected by the parasitic plant striga.

Infection by the hemi-parasitic plant Striga hermonthica causes severe host-plant damage and seed production losses. Increased availability of essential plant nutrients reduces infection. Whether, how and to what extent, it also reduces striga-induced host-plant damage is not well studied. Effects of improved macro- and micronutrient supply on host-plant performance under striga-free and infected conditions were investigated in greenhouse pot assays. One striga-sensitive and two striga-tolerant genotypes were compared. Plants growing in impoverished soils were supplied with (1) 25% of optimal macro- and micronutrients quantities, (2) 25% macro- and 100% micronutrients, (3) 100% macro- and 25% micronutrients, or (4) 100% of macro- and micronutrients. Photosynthesis rates of striga-infected plants of the sensitive genotype increased with improved nutrition (12.2 to 22.1 µmol/m2/s1) but remained below striga-free levels (34.9-38.8 µmol/m2/s1). For the tolerant genotypes, increased macro-nutrient supply offset striga-induced photosynthesis losses. Striga-induced relative grain losses of 100% for the sensitive genotype were reduced to 74% by increased macronutrients. Grain losses of 80% in tolerant Ochuti, incurred at low nutrient supply, were reduced to 5% by improved nutrient supply. Increasing macro-nutrient supply reduces striga impact on host-plants but can only restore losses when applied to genotypes with a tolerant background.

Multi-locus genome-wide association study reveal genomic regions underlying root system architecture traits in Ethiopian sorghum germplasm.

The identification of genomic regions underlying the root system architecture (RSA) is vital for improving crop abiotic stress tolerance. To improve sorghum (Sorghum bicolor L. Moench) for environmental stress tolerance, information on genetic variability and genomic regions linked to RSA traits is paramount. The aim of this study was, therefore, to investigate common quantitative trait nucleotides (QTNs) via multiple methodologies and identify genomic regions linked to RSA traits in a panel of 274 Ethiopian sorghum accessions. Multi-locus genome-wide association study was conducted using 265,944 high-quality single nucleotide polymorphism markers. Considering the QTN detected by at least three different methods, a total of 17 reliable QTNs were found to be significantly associated with root angle, number, length, and dry weight. Four QTNs were detected on chromosome SBI-05, followed by SBI-01 and SBI-02 with three QTNs each. Among the 17 QTNs, 11 are colocated with previously identified root traits quantitative trait loci and the remaining six are genome regions with novel genes. A total of 118 genes are colocated with these up- and down-streams of the QTNs. Moreover, five QTNs were found intragenic. These QTNs are S5_8994835 (number of nodal roots), S10_55702393 (number of nodal roots), S1_56872999 (nodal root angle), S9_1212069 (nodal root angle), and S5_5667192 (root dry weight) intragenic regions of Sobic.005G073101, Sobic.010G198000, Sobic.001G273000, Sobic.009G013600, and Sobic.005G054700, respectively. Particularly, Sobic.005G073101, Sobic.010G198000, and Sobic.009G013600 were found responsible for the plant growth hormone-induced RSA. These genes may regulate root development in the seedling stage. Further analysis on these genes might be important to explore the genetic structure of RSA of sorghum.

Molecular insights into the mutualism that induces iron deficiency tolerance in sorghum inoculated with Trichoderma harzianum

Iron (Fe) deficiency is a common mineral stress in plants, including sorghum. Although the soil fungus Trichoderma harzianum has been shown to mitigate Fe deficiency in some circumstances, neither the range nor mechanism(s) of this process are well understood. In this study, high pH-induced Fe deficiency in sorghum cultivated in pots with natural field soil exhibited a significant decrease in biomass, photosynthetic rate, transpiration rate, stomatal conductance, water use efficiency, and Fe-uptake in both the root and shoot. However, the establishment of T. harzianum colonization in roots of Fe-deprived sorghum showed significant improvements in morpho-physiological traits, Fe levels, and redox status. Molecular detection of the fungal ThAOX1 (L-aminoacid oxidase) gene showed the highest colonization of T. harzianum in the root tips of Fe-deficient sorghum, a location thus targeted for further analysis. Expression studies by RNA-seq and qPCR in sorghum root tips revealed a significant upregulation of several genes associated with Fe uptake (SbTOM2), auxin synthesis (SbSAURX15), nicotianamine synthase 3 (SbNAS3), and a phytosiderophore transporter (SbYS1). Also induced was the siderophore synthesis gene (ThSIT1) in T. harzianum, a result supported by biochemical evidence for elevated siderophore and IAA (indole acetic acid) levels in roots. Given the high affinity of fungal siderophore to chelate insoluble Fe3+ ions, it is likely that elevated siderophore released by T. harzianum led to Fe(III)-siderophore complexes in the rhizosphere that were then transported into roots by the induced SbYS1 (yellow-stripe 1) transporter. In addition, the observed induction of several plant peroxidase genes and ABA (abscisic acid) under Fe deficiency after inoculation with T. harzianum may have helped induce tolerance to Fe-deficiency-induced oxidative stress and adaptive responses. This is the first mechanistic explanation for T. harzianum’s role in helping alleviate Fe deficiency in sorghum and suggests that biofertilizers using T. harzianum will improve Fe availability to crops in high pH environments.

Arbuscular Mycorrhizal (AM) Fungi Symbiosis in Sustainable Production of Sorghum (Sorghum bicolor L. Moench) Under Drought Stress: An Emerging Biofertilizer in Dryland Areas

Sorghum (Sorghum bicolor L. Moench) is an important cereal crop grown in arid and semiarid regions where water and other resources are limited. Changes in temperature and rainfall patterns have resulted in frequent droughts, which caused significant yield loss in sorghum. In recent years, there has been an increasing interest in sorghum cultivation due to its resilience to climate change and potential source of food and income. The symbiotic interaction of sorghum with Arbuscular Mycorrhizal fungi (AMF) has been found to induce several physiological and molecular changes that improve the ability of sorghum to withstand drought stress. This symbiotic relationship enhances water and nutrient uptake, osmotic adjustment, activation of stress‐responsive genes, stomatal regulation, and antioxidant defense, leading to improved drought tolerance in sorghum. Agricultural practices such as reduced tillage, cover cropping, intercropping, crop rotation, and the use of organic amendments promote the diversity and effectiveness of AM fungal symbiosis. Such agricultural practices create more favorable conditions for AM fungal establishment and growth while reducing dependence on synthetic fertilizers. In this review, we highlight AM fungal symbiosis on sorghum growth, physiology, and molecular mechanisms underlying the beneficial effects of AM fungal symbiosis under moisture deficit conditions. Overall, the present review elucidates sorghum production and breeding success in Ethiopia, the symbiotic mechanisms between plants and AM fungi, the prospects of biofertilizers in sustainable agriculture, the potential of AM fungal symbiosis as a sustainable approach to improve sorghum production and its synergistic effect with other crop management practices.

Screening key sorghum germplasms for low-nitrogen tolerance at the seedling stage and identifying from the carbon and nitrogen metabolism.

Sorghum (Sorghum bicolor L.) can withstand drought and heat stress and efficiently utilize water and nutrients. However, the underlying mechanism of its tolerance to low-nitrogen (N) stress remains poorly understood. This study assessed low-N tolerance in 100 sorghum-inbred lines and identified those with exceptional resilience. Principal component analysis, Pearson's correlation, and Y value analysis were used to examine various seedling growth metrics, including plant and root dimensions, biomass, chlorophyll content, root N content, shoot N content, and root/shoot ratio. The genotypes were categorized into four distinct groups based on their respective Y values, revealing a spectrum from highly tolerant to sensitive. Low-N-tolerant sorghum lines maintained higher photosynthetic rates and exhibited increased enzymatic activities linked to carbon and N metabolism in the leaves and roots. Furthermore, low-N-tolerant genotypes had higher levels of key amino acids, including cystine, glycine, histidine, isoleucine, leucine, phenylalanine, threonine, and tyrosine, indicating a robust internal metabolic response to N deficiency. This study provides a comprehensive and reliable approach for the evaluation of sorghum tolerance to low-N environments, sheds light on its morphological and physiological adaptations, and provides valuable insights for future breeding programs and agricultural practices.