Salt Tolerance In Sorghum Research Articles

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.

Melatonin enhances salt tolerance in sorghum by modulating photosynthetic performance, osmoregulation, antioxidant defense, and ion homeostasis.

Melatonin is a potent antioxidant that can prevent plant damage caused by adverse stresses. It remains unclear whether exogenous melatonin can mitigate the effects of salt stress on seed germination and seedling growth of sorghum (Sorghum bicolor (L.) Moench). The aim of this study was to decipher the protective mechanisms of exogenous melatonin (100 μmol/L) on sorghum seedlings under NaCl-induced salt stress (120 mmol/L). Plant morphological, photosynthetic, and physiological characteristics were analyzed at different timepoints after sowing. Results showed that salt stress inhibited seed germination, seedling growth, and plant biomass accumulation by reducing photosynthetic pigment contents, photosynthetic efficiency, root vigor, and mineral uptake. In contrast, seed priming with melatonin enhanced photosynthetic pigment biosynthesis, photosynthetic efficiency, root vigor, and K+ content under salt stress. Melatonin application additionally enhanced the activities of antioxidant enzymes (superoxide dismutase, catalase, ascorbate peroxidase, and glutathione reductase) and increased the levels of non-enzymatic antioxidants (reduced glutathione, ascorbic acid) in the leaves. These changes were accompanied by increase in the leaf contents of soluble sugars, soluble proteins, and proline, as well as decrease in hydrogen peroxide accumulation, malondialdehyde content, and electrolyte leakage. Our findings indicate that exogenous melatonin can alleviate salt stress-induced damage in sorghum seedlings through multifaceted mechanisms, such as improving photosynthetic performance and root vigor, facilitating ion homeostasis and osmoregulation, and promoting antioxidant defense and reactive oxygen species scavenging.

Deciphering the Genetic Mechanisms of Salt Tolerance in Sorghum bicolor L.: Key Genes and SNP Associations from Comparative Transcriptomic Analyses.

Sorghum bicolor L. is a vital cereal crop for global food security. Its adaptability to diverse climates make it economically, socially, and environmentally valuable. However, soil salinization caused by climate extremes poses a threat to sorghum. This study aimed to identify candidate salt-tolerant genes and single nucleotide polymorphisms (SNPs) by performing a comparative transcriptome analysis on a mutant sorghum line and its wild type. The mutant line was generated through gamma ray exposure and selection for salt tolerance. Phenotypic measurements were taken, followed by mRNA sequencing and variant calling. In this study, potential genes and non-synonymous SNPs associated with salt tolerance were inferred, including LOC8071970, LOC8067721, LOC110430887, LOC8070256, and LOC8056880. These genes demonstrated notable differences in nsSNPs in comparison to the wild type, suggesting their potential roles in salt tolerance. Additionally, LOC8060874 (cyanohydrin beta-glucosyltransferase) was suggested as a key gene involved in salt tolerance due to its possible role in dhurrin biosynthesis under salt stress. In upcoming research, additional reverse genetics studies will be necessary in order to verify the function of those candidate genes in relation to salt stress. In conclusion, this study underscores the significance of investigating salt tolerance mechanisms and the potential key genes associated with salt tolerance in sorghum. Our findings may provide insights for future breeding strategies aimed at enhancing salinity tolerance and crop productivity.

Genome-wide identification and expression analysis of the U-box E3 ubiquitin ligase gene family related to salt tolerance in sorghum (Sorghum bicolor L.).

Plant U-box (PUB) E3 ubiquitin ligases play essential roles in many biological processes and stress responses, but little is known about their functions in sorghum (Sorghum bicolor L.). In the present study, 59 SbPUB genes were identified in the sorghum genome. Based on the phylogenetic analysis, the 59 SbPUB genes were clustered into five groups, which were also supported by the conserved motifs and structures of these genes. SbPUB genes were found to be unevenly distributed on the 10 chromosomes of sorghum. Most PUB genes (16) were found on chromosome 4, but there were no PUB genes on chromosome 5. Analysis of cis-acting elements showed that SbPUB genes were involved in many important biological processes, particularly in response to salt stress. From proteomic and transcriptomic data, we found that several SbPUB genes had diverse expressions under different salt treatments. To verify the expression of SbPUBs, qRT-PCR analyses also were conducted under salt stress, and the result was consistent with the expression analysis. Furthermore, 12 SbPUB genes were found to contain MYB-related elements, which are important regulators of flavonoid biosynthesis. These results, which were consistent with our previous multi-omics analysis of sorghum salt stress, laid a solid foundation for further mechanistic study of salt tolerance in sorghum. Our study showed that PUB genes play a crucial role in regulating salt stress, and might serve as promising targets for the breeding of salt-tolerant sorghum in the future.

MicroRNAs balance growth and salt stress responses in sweet sorghum.

Salt stress is one of the major causes of reduced crop production, limiting agricultural development globally. Plants have evolved with complex systems to maintain the balance between growth and stress responses, where signaling pathways such as hormone signaling play key roles. Recent studies revealed that hormones are modulated by microRNAs (miRNAs). Previously, two sweet sorghum (Sorghum bicolor) inbred lines with different salt tolerance were identified: the salt-tolerant M-81E and the salt-sensitive Roma. The levels of endogenous hormones in M-81E and Roma varied differently under salt stress, showing a different balance between growth and stress responses. miRNA and degradome sequencing showed that the expression of many upstream transcription factors regulating signal transduction and hormone-responsive genes was directly induced by differentially expressed miRNAs, whose levels were very different between the two sweet sorghum lines. Furthermore, the effects of representative miRNAs on salt tolerance in sorghum were verified through a transformation system mediated by Agrobacterium rhizogenes. Also, miR-6225-5p reduced the level of Ca2+ in the miR-6225-5p-overexpressing line by inhibiting the expression of the Ca2+ uptake gene SbGLR3.1 in the root epidermis and affected salt tolerance in sorghum. This study provides evidence for miRNA-mediated growth and stress responses in sweet sorghum.

R2R3 MYB transcription factor SbMYBHv33 negatively regulates sorghum biomass accumulation and salt tolerance.

SbMYBHv33 negatively regulated biomass accumulation and salt tolerance in sorghum and Arabidopsis by regulating reactive oxygen species accumulation and ion levels. Salt stress is one of the main types of environmental stress leading to a reduction in crop yield worldwide. Plants have also evolved a variety of corresponding regulatory pathways to resist environmental stress damage. This study aimed to identify a SbMYBHv33 transcription factor that downregulates in salt, drought, and abscisic acid (ABA) in the salt-tolerant inbred line sorghum M-81E. The findings revealed that overexpression of SbMYBHv33 in sorghum significantly reduced sorghum biomass accumulation at the seedling stage and also salinity tolerance. Meanwhile, a heterologous transformation of Arabidopsis with SbMYBHv33 produced a similar phenotype. The loss of function of the Arabidopsis homolog of SbMYBHv33 resulted in longer roots and increased salt tolerance. Under normal conditions, SbMYBHV33 overexpression promoted the expression of ABA pathway genes in sorghum and inhibited growth. Under salt stress conditions, the gene expression of SbMYBHV33 decreased in the overexpressed lines, and the promotion of these genes in the ABA pathway was attenuated. This might be an important reason for the difference in growth and stress resistance between SbMYBHv33-overexpressed sorghum and ectopic expression Arabidopsis. Hence, SbMYBHv33 is an important component of sorghum growth and development and the regulation of salt stress response, and it could negatively regulate salt tolerance and biomass accumulation in sorghum.

Genotypic Divergence, Photosynthetic Efficiency, Sodium Extrusion, and Osmoprotectant Regulation Conferred Salt Tolerance in Sorghum

Genotypic Divergence, Photosynthetic Efficiency, Sodium Extrusion, and Osmoprotectant Regulation Conferred Salt Tolerance in Sorghum

SbWRKY55 regulates sorghum response to saline environment by its dual role in abscisic acid signaling.

SbWRKY55 functions as a key component of the ABA-mediated signaling pathway; transgenic sorghum regulates plant responses to saline environments and will help save arable land and ensure food security. Salt tolerance in plants is triggered by various environmental stress factors and endogenous hormonal signals. Numerous studies have shown that WRKY transcription factors are involved in regulating plant salt tolerance. However, the underlying mechanism for WRKY transcription factors regulated salt stress response and signal transduction pathways remains largely unknown. In this study, the SbWRKY55 transcription factor was found to be the key component for reduced levels of salt and abscisic acid in SbWRKY55 overexpression significantly reduced salt tolerance in sorghum and Arabidopsis. Mutation of the homologous gene AtWRKY55 in A. thaliana significantly enhanced salt tolerance, and SbWRKY55 supplementation in the mutants restored salt tolerance. In the transgenic sorghum with SbWRKY55 overexpression, the expression levels of genes involved in the abscisic acid (ABA) pathway were altered, and the endogenous ABA content decreased. Yeast one-hybrid assays and dual-luciferase reporter assay showed that SbWRKY55 binds directly to the promoter of SbBGLU22 and inhibits its expression level. In addition, both in vivo and in vitro biochemical analyses showed that SbWRKY55 interacts with the FYVE zinc finger protein SbFYVE1, blocking the ABA signaling pathway. This could be an important feedback regulatory pathway to balance the SbWRKY55-mediated salt stress response. In summary, the results of this study provide convincing evidence that SbWRKY55 functions as a key component in the ABA-mediated signaling pathway, highlighting the dual role of SbWRKY55 in ABA signaling. This study also showed that SbWRKY55 could negatively regulate salt tolerance in sorghum.

Expression Profile of Sorghum Genes and Cis-Regulatory Elements under Salt-Stress Conditions.

Salinity stress is one of the most important abiotic stresses that causes great losses in crop production worldwide. Identifying the molecular mechanisms of salt resistance in sorghum will help develop salt-tolerant crops with high yields. Sorghum (Sorghum bicolor (L.) Moench) is one of the world’s four major grains and is known as a plant with excellent adaptability to salt stress. Among the various genotypes of sorghum, a Korean cultivar Nampungchal is also highly tolerant to salt. However, little is known about how Nampungchal responds to salt stress. In this study, we measured various physiological parameters, including Na+ and K+ contents, in leaves grown under saline conditions and investigated the expression patterns of differentially expressed genes (DEGs) using QuantSeq analysis. These DEG analyses revealed that genes up-regulated in a 150 mM NaCl treatment have various functions related to abiotic stresses, such as ERF and DREB. In addition, transcription factors such as ABA, WRKY, MYB, and bZip bind to the CREs region of sorghum and are involved in the regulation of various abiotic stress-responsive transcriptions, including salt stress. These findings may deepen our understanding of the mechanisms of salt tolerance in sorghum and other crops.

Physio-chemical and co-expression network analysis associated with salt stress in sorghum.

Abiotic stress can damage crops and reduce productivity. Among them, salt stress is related to water stress such as osmosis and ions, and like other abiotic stresses, it can affect the growth of plants by changing gene expressions. Investigating the profiles of gene expression under salt stress may help us understand molecular mechanisms of plants to cope with unfavorable conditions. To study salt tolerance in sorghum, physiological and comparative transcriptomic studies were performed using a Korean sorghum cultivar 'Sodamchal' which is considered sensitive to soil salinity. In this study, the samples were treated with two concentrations of NaCl [0 (control) and 150 mM], and the leaves and roots were harvested at 0, 3, and 9 days after the treatment. For the physiological study, the levels of anthocyanin, proline, reducing sugar, and chlorophyll were evaluated in the control and the treatment group at each sampling point. The results show that the cultivar 'Sodamchal' has salt-susceptible profiles. We also analyzed the transcription profile in the presence of 0 and 150 mM NaCl to confirm the candidate genes under the saline stress condition. Between the control and salt treatment, we found a total of 1506 and 1510 differentially expressed genes (DEGs) in the leaves and roots, respectively. We also built a gene co-expression network to determine the association of the candidate genes in terms of biological pathways. Through the co-expression network, genes related to salt stress such as AP2/ERF and Dehydrin were identified. This study provides the physiological and genic markers that could be used during intense salt stress in sorghum. These markers could be used to lay the foundation for the distribution of high-quality seeds that are tolerant to salt in the future.

SbbHLH85, a bHLH member, modulates resilience to salt stress by regulating root hair growth in sorghum.

bHLH family proteins play an important role in plant stress response. However, the molecular mechanism regulating the salt response of bHLH is largely unknown. This study aimed to investigate the function and regulating mechanism of the sweet sorghum SbbHLH85 during salt stress. The results showed that SbbHLH85 was different from its homologs in other species. Also, it was a new atypical bHLH transcription factor and a key gene for root development in sweet sorghum. The overexpression of SbbHLH85 resulted in significantly increased number and length of root hairs via ABA and auxin signaling pathways, increasing the absorption of Na+. Thus, SbbHLH85 plays a negative regulatory role in the salt tolerance of sorghum. We identified a potential interaction partner of SbbHLH85, which was phosphate transporter chaperone PHF1 and modulated the distribution of phosphate, through screening a yeast two-hybrid library. Both yeast two-hybrid and BiFC experiments confirmed the interaction between SbbHLH85 and PHF1. The overexpression of SbbHLH85 led to a decrease in the expression of PHF1 as well as the content of Pi. Based on these results, we suggested that the increase in the Na+ content and the decrease in the Pi content resulted in the salt sensitivity of transgenic sorghum.

Different Sensitivity Levels of the Photosynthetic Apparatus in Zea mays L. and Sorghum bicolor L. under Salt Stress.

The impacts of different NaCl concentrations (0–250 mM) on the photosynthesis of new hybrid lines of maize (Zea mays L. Kerala) and sorghum (Sorghum bicolor L. Shamal) were investigated. Salt-induced changes in the functions of photosynthetic apparatus were assessed using chlorophyll a fluorescence (PAM and OJIP test) and P700 photooxidation. Greater differences between the studied species in response to salinization were observed at 150 mM and 200 mM NaCl. The data revealed the stronger influence of maize in comparison to sorghum on the amount of closed PSII centers (1-qp) and their efficiency (Φexc), as well as on the effective quantum yield of the photochemical energy conversion of PSII (ΦPSII). Changes in the effective antenna size of PSII (ABS/RC), the electron flux per active reaction center (REo/RC) and the electron transport flux further QA (ETo/RC) were also registered. These changes in primary PSII photochemistry influenced the electron transport rate (ETR) and photosynthetic rate (parameter RFd), with the impacts being stronger in maize than sorghum. Moreover, the lowering of the electron transport rate from QA to the PSI end electron acceptors (REo/RC) and the probability of their reduction (φRo) altered the PSI photochemical activity, which influenced photooxidation of P700 and its decay kinetics. The pigment content and stress markers of oxidative damage were also determined. The data revealed a better salt tolerance of sorghum than maize, associated with the structural alterations in the photosynthetic membranes and the stimulation of the cyclic electron flow around PSI at higher NaCl concentrations. The relationships between the decreased pigment content, increased levels of stress markers and different inhibition levels of the function of both photosystems are discussed.

New insights into molecular targets of salt tolerance in sorghum leaves elicited by ammonium nutrition

This study investigated the proteome modulation and physiological responses of Sorghum bicolor plants grown in nutrient solutions containing nitrate (NO3−) or ammonium (NH4+) at 5.0 mM, and subjected to salinity with 75 mM NaCl for ten days. Salinity promoted significant reductions in leaf area, root and shoot dry mass of sorghum plants, regardless of nitrogen source; however, higher growth was observed in ammonium-grown plants. The better performance of ammonium-fed stressed plants was associated with low hydrogen peroxide accumulation, and improved CO2 assimilation and K+/Na+ homeostasis under salinity. Proteomic study revealed a nitrogen source-induced differential modulation in proteins related to photosynthesis/carbon metabolism, energy metabolism, response to stress and other cellular processes. Nitrate-fed plants induced thylakoidal electron transport chain proteins and structural and carbon assimilation enzymes, but these mechanisms seemed to be insufficient to mitigate salt damage in photosynthetic performance. In contrast, the greater tolerance to salinity of ammonium-grown plants may have arisen from: i.) de novo synthesis or upregulation of enzymes from photosynthetic/carbon metabolism, which resulted in better CO2 assimilation rates under NaCl-stress; ii.) activation of proteins involved in energy metabolism which made available energy for salt responses, most likely by proton pumps and Na+/H+ antiporters; and iii.) reprogramming of proteins involved in response to stress and other metabolic processes, constituting intricate pathways of salt responses. Overall, our findings not only provide new insights of molecular basis of salt tolerance in sorghum plants induced by ammonium nutrition, but also give new perspectives to develop biotechnological strategies to generate more salt-tolerant crops.

Comparative Transcriptome Analysis of Seedling Stage of Two Sorghum Cultivars Under Salt Stress

Soil salinity is one of the major abiotic stresses restricting crop production. Mechanisms of salt response have been intensively studied in model plants such as Arabidopsis and rice, but are rarely known in sorghum. In this study, we compared the transcriptome profiles between two cultivars with different salt tolerance under salt treatment (0.8% NaCl) for 0, 48, and 72 h. On average, about 243.9 million clean reads, representing 32.4 thousand transcripts and 26.4 thousand unigenes with 829 new genes were detected in each library. Also, over 112,000 single nucleotide polymorphisms were identified, which may supply useful resources for marker development. In total, 5647 differentially expressed genes (DEGs) were identified from all of the comparisons. Functional annotation analysis indicated that expression of genes in transcriptional regulation, signal transduction, and secondary metabolism changed significantly between the two varieties under salt stress, and hundreds of genes involved in the salt stress response were differentially expressed, especially genes encoding receptors like kinases and transcription factors. Besides, qRT-PCR analysis of expression profiles of the selected DEGs was in keeping with the results from RNA-seq analysis. Based on the findings, we proposed several candidate genes that might be used to improve salt tolerance in sorghum. The transcriptional profiles presented here provide further understanding of the salt-tolerance mechanism in sorghum.

English

In this study, we firstly investigated the germination rate, growth and dry weight of shoots and roots in two sorghum cultivars, Liaoza15 and Longza11, to analysis the physiological responses of sorghum to salt and ABA. We found that Liaoza15 had high salt and ABA tolerance, but Longza11 was hypersensitive to salt and ABA stress during germination and early seedling growth. Secondly, we found that salt-induced ABA accumulation was higher and more sustained in Longza11 than in Liaoza15. Nextly, we analyzed the salt-induced expression of SbABIs in the two sorghum cultivars and AtABIs in wild type Arabidopsis. The result showed that the change in SbABI5 expression in the roots was the most obvious difference between the two cultivars, namely salt did not induce SbABI5 in the roots of Longza11 but increased it by about 3-fold in the roots of Liaoza15. And the salt treatments also increased the expression of AtABI5 in the roots, suggesting changes of SbABI5 expression in the roots is a key step in the ABA signaling pathway to improve salt tolerance in sorghum. Finally, we found that the expression of SbABI5 was strongly induced by relatively low concentrations of ABA rather than by extremely high concentrations of ABA. © 2016 Friends Science Publishers

Silicon-mediated changes in polyamines participate in silicon-induced salt tolerance in Sorghum bicolor L.

Silicon (Si) is generally considered a beneficial element for the growth of higher plants, especially under stress conditions, but the mechanisms remain unclear. Here, we tested the hypothesis that Si improves salt tolerance through mediating important metabolism processes rather than acting as a mere mechanical barrier. Seedlings of sorghum (Sorghum bicolor L.) growing in hydroponic culture were treated with NaCl (100 mm) combined with or without Si (0.83 mm). The result showed that supplemental Si enhanced sorghum salt tolerance by decreasing Na(+) accumulation. Simultaneously, polyamine (PA) levels were increased and ethylene precursor (1-aminocyclopropane-1-carboxylic acid: ACC) concentrations were decreased. Several key PA synthesis genes were up-regulated by Si under salt stress. To further confirm the role of PA in Si-mediated salt tolerance, seedlings were exposed to spermidine (Spd) or a PA synthesis inhibitor (dicyclohexylammonium sulphate, DCHA) combined with salt and Si. Exogenous Spd showed similar effects as Si under salt stress whereas exogenous DCHA eliminated Si-enhanced salt tolerance and the beneficial effect of Si in decreasing Na(+) accumulation. These results indicate that PAs and ACC are involved in Si-induced salt tolerance in sorghum and provide evidence that Si plays an active role in mediating salt tolerance.

Variability in Salt Tolerance of Sorghum bicolor L.

Salt tolerance of ten sorghum (Sorghum bicolor L. Moench) varieties (‘1790E’, ‘BTx642’, ‘Desert Maize’, ‘Macia’, ‘RTx430’, ‘Schrock’, ‘Shallu’, ‘Tx2783’, ‘Tx7078’, and ‘Wheatland’) was evaluated in two greenhouse experiments. In the first experiment, sorghum were sown in substrates moistened with either nutrient solution (no addition of salts, control) at electrical conductivity (EC) of 1.2 dS·m-1 or salt solution at EC 5, 10 or 17 dS·m-1. Seedling emergence percentage decreased in all varieties only at EC of 17 dS·m-1 compared to the control. Seedling emergence percentage of sorghum ‘Macia’ and ‘1790E’ irrigated with salt solution at EC of 17 dS·m-1 decreased by 50% and 51%, while that of ‘RTx430’ reduced by 97%, other varieties ranged from 64% to 90%. Both salt solution at EC of 5 and 10 dS·m-1 reduced the dry weight of sorghum seedlings by 29% and 72% on average, respectively, compared to control. In the 2nd experiment, plants were irrigated with nutrient solution or salt solution at EC of 5.0 or 10.0 dS·m-1 for 30 days. Salt solution at EC of 5.0 and 10.0 dS·m-1 had similar influences on dry weight (DW) of all sorghum varieties except ‘Tx2783’. The relative dry weight of ‘Shallu’, ‘Desert Maize’, and ‘1790E’ irrigated with salt solution at EC of 10 dS·m-1 were over 67%, those of ‘Macia’, ‘Schrock’, and ‘RTx430’ ranged from 30% to 33%, and other varieties were 45% to 59%. Foliar salt damage was observed on all salt-treated sorghum varieties except for ‘Shallu’, which had the lowest shoot DW reduction and greatest visual score. Leaf photosynthesis of all sorghum plants irrigated with salt solution at EC of 5 and 10 dS·m-1 was decreased by 6.0% and 10.6%, respectively. Leaf Na+ concentration at EC of 5.0 and 10.0 dS·m-1 increased by 25.6% and 60.7%, respectively, compared to the control; while Cl- concentration increased by 16.4% and 41.2%, and Ca2+ concentration increased by 17.8% and 34.3%. In conclusion, salt tolerance of sorghum varied with plant growing stage and varieties. ‘Shallu’, ‘Desert Maize’, and ‘1790E’ were the most salt tolerant varieties, while ‘Schrock’ and ‘RTx430’ showed the least salt tolerance in both experiments. All varieties had high Na+ exclusion ability.

Antioxidant-enzymatic system of two sorghum genotypes differing in salt tolerance

Two forage sorghum genotypes were studied: CSF18 (salt-sensitive) and CSF20 (salt-tolerant). Shoot growth reduction as a result of salt stress was stronger in the salt sensitive genotype compared to the salt tolerant one. When the two genotypes were subjected to salt stress (75 mM NaCl) no significant change in lipid peroxidation was observed. However, salt stress induced increases in superoxide dismutase and catalase activities in both genotypes. These salt-induced increases were higher in the salt-tolerant genotype. Peroxidase activity was differentially affected by salt stress in the two genotypes. The activities of these peroxidases were decreased by salt stress in the salt-sensitive genotype and increased in the salt-tolerant genotype. In addition, the activity ratio between the superoxide dismutase and the H2O2-scavenging enzymes was higher in the salt-sensitive genotype. The results obtained support the hypothesis that the higher efficiency of the antioxidant-enzymatic system of the CSF20 genotype could be considered as one of the factors responsible for its tolerance to salt stress. Therefore, it is suggested that the ratio between superoxide dismutase and H2O2-scavenging enzyme activities could be used as a working hypothesis for a biochemical marker for salt tolerance in sorghum.

Salinity Tolerance in Sorghum. II. Cell Culture Response to Sodium Chloride in S. bicolor and S. halepense

Grain sorghum (Sorghum bicolor (L.) Moench], is reported to be less tolerant to salt than the noxious weed and potential biomass energy crop, johnsongrass [S. halepense (L.) Pers.). The objective was to compare callus growth and osmotic responses to salinity of these two sorghum species. Callus was grown for 2 wk in a liquid Murashige and Skoog medium to which NaCl was added to final concentrations of 0.05,0.1, and 0.15 M. Relative fresh weight growth of callus in response to increased salinity in the culture medium was greater in S. halepense than in S. bicolor. After 2 wk of NaCl treatment, brown coloration and apparent necrosis were observed on callus of S. bicolor but not on that of S. halepense. The Na/K ratios were lower in callus of S. halepense than that of S. bicolor at all NaCl concentrations. Total amino acids in salinized callus did not change, but proline increased; this increase was greater in S. halepense callus than in that of S. bicolor. Levels of Na and Cl were larger in S. halepense callus treated with 0.1S mM NaCl and these were associated with a ψp of 0.40 MPa, whereas a ψp of 0.26 MPa was observed in callus of S. bicolor. Accumulation of NaCl accounted for three‐fourths of the solutes involved in osmotic adjustment in the callus of both species. Growth and Na/K ratios in salinized callus in this study were correlated with whole plant responses determined in another study. Callus growth and Na/K ratios could therefore be used as indicators of whole plant salt tolerance in Sorghum.

The Response of Four Sorghum Accessions/Cultivars to Salinity During Plant Development

AbstractWhole‐plant‐response of four sorghum accessions to increasing mM NaCl concentrations of 0, 100, and 150 was assessed at three growth stages (GS‐1, GS‐2, and GS‐3), in a sand‐culture experiment. Accession comparisons were made on the basis of absolute and relative salt tolerance values. Increasing salinity significantly reduced plant height at GS‐1, whilst shoot and root dry weight were less affected. The effect of NaCl on these characters was greater at GS‐2 and GS‐3, and accessions differed significantly in their responses to salinity. On the basis of plant height data, Giza 114 had the highest absolute salt tolerance at all three growth stages. However based on shoot and root dry weight data, Double TX and Giza 114 were both significantly more NaCl‐tolerant than INRA 133 and INRA 353 at GS‐2. Based on relative salt tolerance values of shoot and root dry weight, and plant height, Double TX and Giza 114 were more affected by salinity at GS‐3 than INRA 133 and INRA 353. INRA 133 and INRA 353 exhibited progressively higher tolerance at all growth stages, and produced more grains than Double TX and Giza 114, and consequently had higher grain yield per plant. NaCl salinity had little effect on grain weight. Plant sensitivity to NaCl at three growth stages differs in the four accessions, and is genotype‐specific. This suggests that there is considerable variation in salt tolerance in sorghum at the adult stage which may be exploited through selection and breeding of plants to effect further improvement in salinity tolerance in this species.