Seedling Resistance Research Articles

Exogenous melatonin delays leaves senescence and enhances saline and alkaline stress tolerance in grape seedlings

ABSTRACT Saline and alkaline stress is one of the major abiotic stresses facing agricultural production, which severely inhibits the growth and yield of plant. The application of plant growth regulators can effectively prevent crop yield reduction caused by saline and alkaline stress. Exogenous melatonin (MT) can act as a signaling molecule involved in the regulation of a variety of physiological processes in plants, has been found to play a key role in enhancing the improvement of plant tolerance to abiotic stresses. However, the effects of exogenous MT on saline and alkaline tolerance of table grape seedlings and its mechanism have not been clarified. The aim of this study was to investigate the role of exogenous MT on morphological and physiological growth of table grape seedlings ( Vitis vinifera L.) under saline and alkaline stress. The results showed that saline and alkaline stress resulted in yellowing and wilting of grape leaves and a decrease in chlorophyll content, whereas the application of exogenous MT alleviated the degradation of chlorophyll in grape seedling leaves caused by saline and alkaline stress and promoted the accumulation of soluble sugars and proline content. In addition, exogenous MT increased the activity of antioxidant enzymes, which resulted in the scavenging of reactive oxygen species (ROS) generated by saline and alkaline stress. In conclusion, exogenous MT was involved in the tolerance of grape seedlings to saline and alkaline stress, and enhanced the saline and alkaline resistance of grape seedlings to promote the growth and development of the grape industry in saline and alkaline areas.

Genetic Diversity for Effective Resistance in Wheat Landraces from Ethiopia and Eritrea to Fungal Diseases and Toxic Aluminum Ions.

To reveal genetic diversity for effective resistance to five foliar diseases and toxic aluminum ions, the entire collection of wheat species from the N.I. Vavilov All-Russian Institute of Plant Genetic Resources (VIR) originating from Ethiopia and Eritrea were studied regarding their traits. The collection contains 509 samples of four wheat species (Triticum aestivum-122 samples; T. aethiopicum-340 samples; T. polonicum-6 samples; and T. dicoccum-41 samples). The majority of accessions are new entries of landraces added to the Vavilov collection as a result of the Russian-Ethiopian expedition in 2012. Wheat seedlings were inoculated with causal agents of leaf rust (Pt), powdery mildew (Bgt), Septoria nodorum blotch (SNB), and dark-brown leaf spot blotch (HLB). The types of reaction and disease development were assessed to describe the levels of resistance. All samples of T. aethiopicum were also screened for seedling and adult resistance to Pt, Bgt, and yellow rust (Pst) under field conditions after double inoculation with the corresponding pathogens. To study tolerance to abiotic stress, seedlings were grown in a solution of Al3+ (185 µM, pH 4,0) and in water. The index of root length was used to characterize tolerance. Seedlings belonging to only two accessions out of those studied-k-68236 of T. aethiopicum and k-67397 of T. dicoccum-were resistant to Pt at 20 °C but susceptible at 25 °C. Specific molecular markers closely linked to the five genes for Pt resistance effective against populations of the pathogen from the northwestern region of Russia were not amplified in these two entries after PCR with corresponding primers. Four entries of T. dicoccum-k-18971, k-18975, k-19577, and k-67398-were highly resistant to Bgt. All samples under study were susceptible to HLB and SNB. Under field conditions, 15% of the T. aethiopicum samples were resistant to Pst, both at the seedling and the flag leaf stages, but all were susceptible to the other diseases under study. Among the evaluated samples, 20 entries of T. aestivum, 1 of T. polonicum (k-43765), and 2 of T. dicoccum (k-18971, k-67397) were tolerant to aluminum ions. The identified entries could be valuable sources for the breeding of T. aestivum and other wheats for resistance to biotic and abiotic stresses.

Involvement of ROS and calcium ions in developing heat resistance and inducing antioxidant system of wheat seedlings under melatonin's effects.

The stress-protective effect of melatonin (N-acetyl-5-methoxytryptamine) on plant cells is mediated by key signaling mediators, in particular calcium ions and reactive oxygen species (ROS). However, the links between changes in calcium and redox homeostasis and the formation of adaptive responses of cultivated cereals (including wheat) to the action of high temperatures have not yet been studied. In the present study, we investigated the possible involvement of ROS and calcium ions as signaling mediators in developing heat resistance in wheat (Triticum aestivum L.) seedlings and activating their antioxidant system. Treatment of 3-day-old etiolated seedlings with melatonin solutions at concentrations 0.01-10µM increased their survival after exposure to 45°C for 10min. The most significant stress-protective effect was exerted by melatonin treatment at 1µM concentration. Under the influence of melatonin, a transient enhancement of superoxide anion radical (O2•-) generation and an increase in hydrogen peroxide content were observed in roots, with a maximum at 1h. Four hours after treatment with melatonin, the activity of catalase and guaiacol peroxidase increased in roots, while the activity of superoxide dismutase did not change significantly. After exposure to 45°C, the activity of catalase and guaiacol peroxidase was higher in the roots of melatonin-treated wheat seedlings, and the indices of ROS generation, content of the lipid peroxidation product malonic dialdehyde, and cell membrane damage were lower than in control seedlings. Melatonin-induced changes in root ROS generation and antioxidant enzyme activities were eliminated by pretreatment with the hydrogen peroxide scavenger dimethylthiourea (DMTU), NADPH oxidase inhibitor imidazole, and calcium antagonists (the extracellular calcium chelator EGTA and phospholipase C inhibitor neomycin). Treatment with DMTU, imidazole, EGTA, and neomycin also abolished the melatonin-induced increase in survival of wheat seedlings after heat stress. The role of calcium ions and ROS, generated with the participation of NADPH oxidase, as signaling mediators in the melatonin-induced antioxidant system and heat stress resistance of wheat seedlings have been demonstrated.

Evaluation of stripe rust resistance and genome-wide association study in wheat varieties derived from the International Center for Agricultural Research in the Dry Areas.

159 wheat varieties obtained from ICARDA, CYR32, CYR33 and CYR34 were used to evaluate the stripe rust resistance in this study. Seedling resistance was carried out in the green house at the two-leaf stage. Adult-plant resistance was carried out between 2022 and 2023 in Xining and Guide, respectively. A total of 24,151 high-quality SNP loci were obtained from a 55K SNP chip data. Genome-wide association study was carried out between SNP loci and stripe rust resistance. Seedling resistance screening revealed that 91.8% (146) of wheat varieties were resistant to CYR32 and CYR33, while only 49.7% (79) of wheat varieties were resistant to CYR34. Adult-plant resistance showed 153 (96.2%) germplasms represented resistance in 2022, while only 85 (53.4%) showed resistance in 2023. An association study using the 55K SNP chip data results combined with disease ratings of 159 materials at both the seedling and adult stages discovered 593 loci related to stripe rust resistance (P ≤ 0.0001). These loci exhibited contribution rates ranging from 11.1% to 18.7%. Among them, 71 were significantly related to resistance against CYR32 at the seedling stage, with a contribution rate of 12.7%-17.2%. Constituting the vast majority, 518 loci distributed across 21 chromosomes were significantly related to CYR33 at the seedling stage, with a contribution rate of 12.6%-18.7%. Fewer loci were found to be associated with disease resistance in adult plants. In E1 environment, a sole locus was detected on chromosome 2B with a contribution rate of 14.4%. In E2 environment, however, exhibited three loci across chromosomes 2B, 4A, and 7B with contribution rates ranging from 11.1% to 16.9%. A total of 68 multi-effect loci were significantly related to resistance against both CYR32 and CYR33 at the seedling stage, and one stable locus was significantly associated with stripe rust resistance at the adult plant stage.

Exogenous Streptomyces spp. enhance the drought resistance of naked oat (Avena nuda) seedlings by augmenting both the osmoregulation mechanisms and antioxidant capacities.

Drought is a major obstacle to the development of naked oat industry. This work investigated mechanisms by which exogenous Streptomyces albidoflavus T4 and Streptomyces rochei D74 improved drought tolerance in naked oat (Avena nuda ) seedlings. Results showed that in the seed germination experiment, germination rate, radicle and hypocotyl length of naked oat seeds treated with the fermentation filtrate of T4 or D74 under PEG induced drought stress increased significantly. In the hydroponic experiment, the shoot and root dry weights of oat seedlings increased significantly when treated with the T4 or D74 fermentation filtrate under the 15% PEG induced drought stress (S15). Simultaneously, the T4 treatment also significantly increased the surface area, volume, the number of tips and the root activity of oat seedlings. Both T4 and D74 treatments elicited significant increases in proline and soluble sugar contents, as well as the catalase and peroxidase activities in oat seedlings. The results of comprehensive drought resistance capacity (CDRC) calculation of oat plants showed that the drought resistance of oat seedlings under the T4 treatment was better than that under the D74 treatment, and the effect was better under higher drought stress (S15). Findings of this study may provide a novel and effective approach for enhancing plant defenses against drought stress.

Tea-Derived Polyphenols Enhance Drought Resistance of Tea Plants (Camellia sinensis) by Alleviating Jasmonate-Isoleucine Pathway and Flavonoid Metabolism Flow.

Extreme drought weather has occurred frequently in recent years, resulting in serious yield loss in tea plantations. The study of drought in tea plantations is becoming more and more intensive, but there are fewer studies on drought-resistant measures applied in actual production. Therefore, in this study, we investigated the effect of exogenous tea polyphenols on the drought resistance of tea plant by pouring 100 mg·L-1 of exogenous tea polyphenols into the root under drought. The exogenous tea polyphenols were able to promote the closure of stomata and reduce water loss from leaves under drought stress. Drought-induced malondialdehyde (MDA) accumulation in tea leaves and roots was also significantly reduced by exogenous tea polyphenols. Combined transcriptomic and metabolomic analyses showed that exogenous tea polyphenols regulated the abnormal responses of photosynthetic and energy metabolism in leaves under drought conditions and alleviated sphingolipid metabolism, arginine metabolism, and glutathione metabolism in the root system, which enhanced the drought resistance of tea seedlings. Exogenous tea polyphenols induced jasmonic acid-isoleucine (JA-ILE) accumulation in the root system, and the jasmonic acid-isoleucine synthetase gene (TEA028623), jasmonic acid ZIM structural domain proteins (JAMs) synthesis genes (novel.22237, TEA001821), and the transcription factor MYC2 (TEA014288, TEA005840) were significantly up-regulated. Meanwhile, the flavonoid metabolic flow was significantly altered in the root; for example, the content of EGCG, ECG, and EGC was significantly increased. Thus, exogenous tea polyphenols enhance the drought resistance of tea plants through multiple pathways.

Identification of synthetic wheat lines with broadly effective stripe rust resistance

Wheat stripe/yellow rust (WYR), caused by Puccinia striiformis f. sp. tritici (Pst), is a major constraint in global wheat production. A set of 766 hexaploid synthetic wheat lines, including primary crosses of Triticum turgidum x Aegilops tauschii and their derivatives, were screened in artificially rust inoculated field nurseries for three seasons. From this set, a core set of 94 non-lodging lines with unique pedigrees and resistance to Pst that was consistent across years was established. The core set was tested for adult plant field response under field conditions for three seasons in Australia and at least one crop season in Ethiopia, India, Kenya, Nepal and Pakistan. It was also challenged with an array of well-defined Pst pathotypes at seedling growth stages in the greenhouse, and genotyped with molecular markers linked to the adult plant resistance (APR) genes Yr18, Yr36 and Yr46. Combined analysis of field rust responses, multi-pathotype seedling phenotyping and marker genotyping resolved seven classes of Pst resistance: uncatalogued (new) APR (UAPR, 11%), uncatalogued seedling resistance (USR, 46%), known seedling resistance (KSR, 5%), KSR + USR (2%), Yr18 + UAPR (4%), Yr18 + USR (29%) and Yr18 + KSR (3%). A majority of the lines carrying UAPR and USR either singly or in combination showed high levels of field resistance across all field sites and years of testing, demonstrating that these lines represent a valuable resource for breeding wheat for resistance to Pst.

Molecular mechanisms of regulation of anthocyanine biosynthesis, photosynthesis, and frost resistance of winter wheat seedlings treated with the 5-aminolevulic acid

It was found that in anthocyanin-enriched coleoptiles of winter wheat EtW5 variety, the exogenous 5-aminolevulinic acid (ALA) increased the content of anthocyanins by a factor of 1.5 and the expression level of structural (PAL, CHS) and regulatory (PAP-1) genes of the anthocyanin biosynthesis pathway. In coleoptiles of Vladi plants containing 33 times less anthocyanins compared to EtW5, the expression of CHS and PAP-1 was reduced and additionally inhibited by ALA. Thus, the genetic activity of the phenylpropanoid and flavonoid sites of the anthocyanin biosynthesis pathway shows distinct variety specificity and a dependence on the level of anthocyanins. ALA significantly reduced the thermal dissipation of excitation energy in PSII complexes in the EtW5 variety enriched with anthocyanins and significantly increased the level of these processes in the Vladi variety. Variety-specificity was noted in the levels of frost resistance of two varieties – high (88 % of surviving plants exposed to a temperature of –8 °С for 5 hours) in the EtW5 variety and lower (80 %) in the Vladi variety. ALA increased the frost resistance of both varieties due to an increase in the content of anthocyanins and proline in the coleoptiles of the EtW5 variety and a higher proline content in the Vladi variety.

Genome-wide identification and expression analysis of the Dof gene family reveals their involvement in hormone response and abiotic stresses in sunflower (Helianthus annuus L.)

DNA binding with one finger (Dof), plant-specific zinc finger transcription factors, can participate in various physiological and biochemical processes during the life of plants. As one of the most important oil crops in the world, sunflower (Helianthus annuus L.) has significant economic and ornamental value. However, a systematic analysis of H. annuus Dof (HaDof) members and their functions has not been extensively conducted. In this study, we identified 50 HaDof genes that are unevenly distributed on 17 chromosomes of sunflower. We present a comprehensive overview of the HaDof genes, including their chromosome locations, phylogenetic analysis, and expression profile characterization. Phylogenetic analysis classified the 366 Dof members identified from 11 species into four groups (further subdivided into nine subfamilies). Segmental duplications are predominantly contributed to the expansion of sunflower Dof genes, and all segmental duplicate gene pairs are under purifying selection due to strong evolutionary constraints. Furthermore, we observed differential expression patterns for HaDof genes in normal tissues as well as under hormone treatment or abiotic stress conditions by analyzing RNA-seq data from previous studies and RT-qPCR data in our current study. The expression of HaDof04 and HaDof43 were not detected in any samples, which implied that they may be gradually undergoing pseudogenization process. Some HaDof genes, such as HaDof25 and HaDof30, showed responsiveness to exogenous plant hormones, such as kinetin, brassinosteroid, auxin or strigolactone, while others like HaDof15 and HaDof35 may participate in abiotic stress resistance of sunflower seedling. Our study represents the initial step towards understanding the phylogeny and expression characterization of sunflower Dof family genes, which may provide valuable reference information for functional studies on hormone response, abiotic stress resistance, and molecular breeding in sunflower and other species.

Physiological and Transcriptomic Analyses Reveal the Mechanisms Underlying Methyl Jasmonate-Induced Mannitol Stress Resistance in Banana.

Exogenous methyl jasmonate (MeJA) application has shown promising effects on plant defense under diverse abiotic stresses. However, the mechanisms underlying MeJA-induced stress resistance in bananas are unclear. Therefore, in this study, we treated banana plants with 100 μM MeJA before inducing osmotic stress using mannitol. Plant phenotype and antioxidant enzyme activity results demonstrated that MeJA improved osmotic stress resistance in banana plants. Thereafter, to explore the molecular mechanisms underlying MeJA-induced osmotic stress resistance in banana seedlings, we conducted high-throughput RNA sequencing (RNA-seq) using leaf and root samples of "Brazilian" banana seedlings treated with MeJA for 0 h and 8 h. RNA-seq analysis showed that MeJA treatment upregulated 1506 (leaf) and 3341 (root) genes and downregulated 1768 (leaf) and 4625 (root) genes. Then, we performed gene ontology and Kyoto Encyclopedia of Genes and Genomes analyses on the differentially expressed genes. We noted that linoleic acid metabolism was enriched in both root and leaf samples, and the genes of this pathway exhibited different expression patterns; 9S-LOX genes were highly induced by MeJA in the leaves, whereas 13S-LOX genes were highly induced in the roots. We also identified the promoters of these genes, as the differences in response elements may contribute to tissue-specific gene expression in response to MeJA application in banana seedlings. Overall, the findings of this study provide insights into the mechanisms underlying abiotic stress resistance in banana that may aid in the improvement of banana varieties relying on molecular breeding.

Evaluation and genetic dissection of the powdery mildew resistance in 558 wheat accessions

Powdery mildew, a widespread and destructive wheat disease caused by the fungal pathogen Blumeria graminis f. sp. tritici (Bgt), results in significant yield losses globally. Employing host resistance is the most cost-effective and environmentally sustainable approach to managing this disease. Assessing the resistance levels of wheat germplasms and understanding the genetic underpinnings of this resistance is crucial. In this study, we evaluated the seedling resistance to powdery mildew in 558 wheat accessions, along with the presence of resistance genes Pm1, Pm2, Pm4, Pm5, Pm6, Pm8, Pm12, Pm21, Pm24, Pm41, Pm42, Pm45, Pm47, Pm60, and Pm69 using various Bgt isolates and associated diagnostic markers. The study revealed that out of 558 wheat accessions tested, only 25 showed resistance to the Bgt isolate E09, highlighting a general lack of powdery mildew resistance among the evaluated accessions. Furthermore, these 25 accessions exhibited a significantly different resistance spectrum to 25 additional Bgt isolates. Notably, seven of these accessions were resistant to all the tested isolates, indicating they possess Pm genes with broad-spectrum resistance. Molecular analysis using closely linked or diagnostic markers revealed diverse resistance gene profiles: 249 accessions harbored a single tested Pm gene, 75 accessions possessed combinations of Pm genes, and 234 accessions lacked any of the tested genes. Pm8 was the most frequently detected gene, present in 27.42% of accessions, whereas Pm5, Pm12, Pm24, Pm41, Pm42, Pm45, Pm47 and Pm69 were not detected. Among the seven accessions resistant to all 26 tested isolates, Pm21 was detected in four accessions (HengS29, Chang 4640, Xinong 556, and ML728). Pm2 and Pm60 were identified in Emai 18 and Xinmai 296, respectively. Interestingly, none of the tested genes were detected in Emai 16, suggesting the presence of potentially novel Pm gene(s) conferring broad-spectrum resistance. These findings offer valuable insights for the strategic dissemination of these resistant accessions and for targeted breeding programs aimed at combating powdery mildew.

Genome-wide association mapping for seedling and adult resistance to powdery mildew in barley

Key messageTwo new major QTL were identified for powdery mildew resistance. We confirmed that the QTL on 7HS contributed mainly to the adult-plant resistance, while another one on chromosome arm 1HS made a significant contribution to the seedling resistance.Powdery mildew (PM), caused by Blumeria hordei, can occur at all post emergent stages of barley and constantly threatens crop production. To identify more genes for effective resistance to powdery mildew for use in breeding programs, 696 barley accessions collected from different regions of the world were evaluated for PM resistance at seedling and adult growth stages in three different states of Australia. These barley accessions were genotyped using DArTSeq with over 18,000 markers for a genome-wide association study (GWAS). Using the FarmCPU model, 54 markers showed significant associations with PM resistance scored at the seedling and adult-plant stages in different states of Australia. Another 40 markers showed tentative associations (LOD > 4.0) with resistance. These markers are distributed across all seven barley chromosomes. Most of them were grouped into eleven QTL regions, coinciding with the locations of most of the reported resistance genes. Two major MTAs were identified on chromosome arms 3HS and 5HL, with one on 3HS contributing to adult plant resistance and the one on 5HL to both seedling and adult plant resistance. An MTA on 7HS contributed mainly to the adult-plant resistance, while another one on chromosome arm 1HS made a significant contribution to the seedling resistance.

Drought priming reduces Calligonum mongolicum sensitivity to recurrent droughts via coordinated regulation of osmolytes, antioxidants, and hormones.

Pre-exposure of plants to abiotic stressors may induce stress memory and improve tolerance to subsequent stresses. Here, 3-month-old Calligonum mongolicum seedlings were exposed to drought (60 days) with (primed) or without (unprimed) early drought exposure of 50 days, to determine whether this enhances seedling resistance and investigate possible underlying mechanisms. Compared to unprimed, primed seedlings had higher biomass, shoot relative water content (15% and 22%), chlorophyll a, chlorophyll b, and carotenoids. They also had more superoxide anions (O2 -• ) and H2 O2 scavenging mechanisms through higher activity of SOD, CAT, APX, and dehydroascorbate reductase in assimilating shoots and roots, resulting in less ROS and oxidative stress damage. Plants also had higher ABA and JA but lower SA, likely reflecting an adaptive response to subsequent stress. Primed seedlings accumulated more IAA and brassinosteroids, which may account for their better growth. Accumulation of glycine betaine, pro, and total amino acids in assimilating shoots and roots of primed seedlings led to reduced osmotic stress. Drivers of responses of non-primed and primed seedlings to drought varied. Responses of primed seedlings were primarily characterized by more photosynthetic pigments, increased oxidative scavenging of O2 -• and H2 O2 , more phytohormones and osmolytes. Early drought priming of drought stress memory in C. mongolicum seedlings may provide a useful management approach to improve seedling establishment in vegetation restoration programs.

Carbon monoxide is involved in melatonin-enhanced drought resistance in tomato seedlings by enhancing chlorophyll synthesis pathway

BackgroundDrought is thought to be a major abiotic stress that dramatically limits tomato growth and production. As signal molecule, melatonin (MT) and carbon monoxide (CO) can enhance plant stress resistance. However, the effect and underlying mechanism of CO involving MT-mediated drought resistance in seedling growth remains unknown. In this study, tomato (Solanum lycopersicum L. ‘Micro-Tom’) seedlings were used to investigate the interaction and mechanism of MT and CO in response to drought stress.ResultsThe growth of tomato seedlings was inhibited significantly under drought stress. Exogenous MT or CO mitigated the drought-induced impairment in a dose-dependent manner, with the greatest efficiency provided by 100 and 500 µM, respectively. But application of hemoglobin (Hb, a CO scavenger) restrained the positive effects of MT on the growth of tomato seedlings under drought stress. MT and CO treatment promoted chlorophyll a (Chl a) and chlorophyll a (Chl b) accumulations. Under drought stress, the intermediate products of chlorophyll biosynthesis such as protoporphyrin IX (Proto IX), Mg-protoporphyrin IX (Mg-Proto IX), potochlorophyllide (Pchlide) and heme were increased by MT or CO, but uroporphyrinogen III (Uro III) content decreased in MT-treated or CO-treated tomato seedlings. Meanwhile, MT or CO up-regulated the expression of chlorophyll and heme synthetic-related genes SlUROD, SlPPOX, SlMGMT, SlFECH, SlPOR, SlChlS, and SlCAO. However, the effects of MT on chlorophyll biosynthesis were almost reversed by Hb.ConclusionThe results suggested that MT and CO can alleviate drought stress and facilitate the synthesis of Chl and heme in tomato seedlings. CO played an essential role in MT-enhanced drought resistance via facilitating chlorophyll biosynthesis pathway.

Evaluation of Resistance Resources and Analysis of Resistance Mechanisms of Maize to Stalk Rot Caused by Fusarium graminearum.

Stalk rot is one of the most destructive and widely distributed diseases in maize plants worldwide. Research on the performance and resistance mechanisms of maize against stem rot is constantly improving. In this study, among 120 inbred maize lines infected by Fusarium graminearum using the injection method, 4 lines (3.33%) were highly resistant to stalk rot, 28 lines (23.33%) were resistant, 57 lines (47.50%) were susceptible, and 31 lines (25.84%) were highly susceptible. The inbred lines 18N10118 and 18N10370 were the most resistant and susceptible with disease indices of 7.5 and 75.6, respectively. Treatment of resistant and susceptible maize inbred seedlings with F. graminearum showed that root hair growth of the susceptible inbred lines was significantly inhibited, and a large number of hyphae attached and adsorbed multiple conidia near the root system. However, the resistant inbred lines were delayed and inconspicuous, with only a few hyphae and spores appearing near the root system. Compared with susceptible inbred lines, resistant maize inbred line seedlings treated with F. graminearum exhibited elevated activities of catalase, phenylalanine ammonia-lyase, polyphenol oxidase, and superoxide dismutase. We identified 153 genes related to disease resistance by transcriptome analysis. The mitogen-activated protein kinase signaling and peroxisome pathways mainly regulated the resistance mechanism of maize inbred lines to F. graminearum infection. These two pathways might play an important role in the disease resistance mechanism, and the function of genes in the two pathways must be further studied, which might provide a theoretical basis for further understanding the molecular resistance mechanism of stalk rot and resistance gene mining.

Resistance of oil palm seedlings against red spider mite attack through boron fertilizer application

Resistance of oil palm seedlings against red spider mite attack through boron fertilizer application

Interação de plântulas de soja com rizobactérias benéficas

Beneficial rhizobacteria are multifunctional microorganisms that stimulate plant growth through direct mechanisms such as the solubilization of phosphorus and potassium present in soil minerals, biological nitrogen fixation and production of plant hormones. The objective of this study was to determine the effect of beneficial rhizobacteria on the initial development, promoting growth and resistance of soybean seedlings, aiming not only for increased production but also for agricultural sustainability through the maximization of biological efficiency in the early development of soybean seedlings. The experiment, under controlled conditions, was conducted in a completely randomized design, with four treatments and ten replications. The treatments consisted in the microbiolization of soybean seeds with: 1. Control (without microorganism); 2. Serratia marcenses (BRM 32114); 3. Bacillus spp. (BRM63573) and 4. BRM 32114 + (BRM63573). After the microbiolization of the seeds, they were sown and placed to germinate, after 12 days, the seedlings were harvested and divided into shoots and roots. The roots were washed and photographed with digital camera. The images were analyzed and determined length, diameter, surface area and volume of roots. Then, root and shoot were dried and weighed for biomass determination. Co-inculation, BRM 32114+ BRM63573, promoted greater robustness of the root system of soybean seedlings with increased length (16.2%), diameter (22.5%), volume (43.4%) and dry biomass (29.7%). The dry matter of shoots and total soybean seedlings was superior to the control treatment in all treatments with rhizobacteria. Therefore, plant growth promoting

Effect of Pulsed Electric Field Treatment on Seed Germination and Seedling Growth of Scutellaria baicalensis

To explore the effects of pulsed electric field treatment on the germination of Scutellaria baicalensis seeds and the growth of seedlings, this study used the response surface methodology to design the working parameters of the pulsed electric field and treated and cultured Scutellaria baicalensis seeds. The results showed that the pulsed electric field treatment was beneficial for the germination of Scutellaria baicalensis seeds, improving the metabolic activity and stress resistance of seedlings. When the pulsed electric field treatment’s parameters were 0.5 kV·cm−1, 120 μs, and 99 pulses, the germination potential of seeds was significantly increased by 29.25% and the germination index significantly increased by 20.65%, compared to the control. From 5th to 15th day, the activities of SOD, POD, and α-amylase in the seedlings, and the contents of Pro, soluble sugars, and soluble proteins were significantly increased, compared to the control. This study provides a theoretical basis for improving the germination and seedling growth of medicinal herbs such as Scutellaria baicalensis and their practical application in production.

Mechanisms involved in plant growth promotion by Enterobacter cloacae DJ under salinity-alkalinity stress

BackgroundPlant-promoting bacteria are safer alternatives to pesticides and fertilizers, reduce environmental pollution, and increase crop yields. We isolated an Enterobacter cloacae strain DJ with plant-promoting effects from the rhizosphere soil of a plant (Leymus chinensis (Trin.) Tzvel) in the western region of Jilin Province of China and investigated the mechanisms underlying the adaptation of the DJ bacteria to salinity-alkalinity environments and the molecular mechanisms of the cross-talk between DJ bacteria and cucumber seedlings.ResultsThe average diameter of the colonies on the salinity-alkalinity medium after incubation for 24 h was 3.3 cm, and this was significantly higher than the 1.9 cm diameter in ADF medium (p < 0.01). Comparative proteomic analysis revealed that 188 differentially expressed proteins, comprising 116 upregulated and 72 downregulated proteins, significantly changed in salinity-alkalinity groups compared to the control groups. The top one upregulated pathway of KEGG enrichment was bacterial chemotaxis, DJ bacteria adapted to salinity-alkalinity environments by upregulating the genes associated with bacterial chemotaxis. The contents of putrescine in salinity-alkalinity and control groups were 4.73 μg/mL and 3.02 μg/mL, whereas the contents of spermidine were 46.18 ng/mL and 0.34 ng/mL, respectively. Comparing to the control cohorts, the concentrations of both polyamines in the experimental cohorts exhibited statistically significant increases (p < 0.01). The expression of Pt gene encoding polyamine transporter protein was sharply up-regulated in cucumber roots after treatment with DJ bacteria under salinity-alkalinity stress; the expression was more than tenfold higher than that in the control groups. The enzyme activities of POD, SOD, and CAT in cucumber seedlings were higher compared to those in the control groups (p < 0.01). The stem height, number of lateral roots, and fresh weight of cucumber seedlings in the DJ treatment groups were 6.0 cm, 17 roots, and 0.42 g, respectively, whereas those of the control groups were 3.8 cm, 14 roots, and 0.28 g, respectively, with a notable difference between two cohorts (p < 0.01).ConclusionsDJ bacteria can live in salinity-alkalinity conditions by upregulating the expression of genes associated with chemotaxis. The resistance of cucumber seedlings under salinity-alkalinity conditions through the antioxidant pathway was increased by polyamines produced by DJ bacteria.Graphical

Effects of exogenous GABA on physiological characteristics of licorice seedlings under saline-alkali stress

Licorice is widespread in arid and semi-arid areas, but high soil salinity has always been a limiting factor for vegetation growth in these areas. Gamma-aminobutyric acid (GABA) is a signaling molecule that can regulate tolerance in plant. However, the mechanism by which exogenous GABA regulates the response of licorice to saline-alkali stress is not yet clear. In this study, we investigated the effects of exogenous GABA on growth parameters, oxidative damage, hormone levels and photosynthetic indices of licorice seedlings under different combinations of saline and alkali stress conditions. The experiment involved eight treatments: CK, distilled water (control); CK + GABA, 0.1 mM GABA; salt stress (SS), 150 mM NaCl; SS + GABA, 150 mM NaCl + 0.1 mM GABA; alkali stress (AS), 10 mM Na2CO3; AS + GABA, 10 mM Na2CO3 + 0.1 mM GABA; mixed saline-alkali stress (MAS), 150 mM NaCl + 10 mM Na2CO3; MAS + GABA, 150 mM NaCl + 10 mM Na2CO3 + 0.1 mM GABA. Our results showed that the inhibitory effects of SS and MAS on the seedling height, root length and root-shoot ratio were significantly alleviated by exogenous GABA. Although soluble sugars, chlorophyll a, total chlorophyll, and superoxide dismutase (SOD) activity were lower in the leaves of the seedlings in the SS treatment compared with the control, these physiological parameters increased significantly after GABA application. Exogenous GABA improved glutathione (GSH) activity in both the leaves and roots of the seedlings during the AS treatment. Additionally, take advantage of GABA led to an increase in ABA, GA and IAA contents in leaves under SS, AS and MAS treatments. Furthermore, the photosynthetic parameters, including Pn, gs, Tr, ETR and qP, significantly increased following the utilization of GABA in both the SS and MAS treatments. Therefore, the application of exogenous GABA can reduce the accumulation of harmful substances, preserve cell morphology, and enhance cell function under saline, alkali, and saline-alkali stress. This enhances the resistance of licorice seedlings to stress conditions and reduces physiological damage.