Seedling Resistance Research Articles

Genome-wide identification, classification, and expression analysis of heat shock transcription factor family in switchgrass (Panicum virgatum L.)

Switchgrass is one of the most promising bioenergy crops and is generally cultivated in arid climates and poor soils. Heat shock transcription factors (Hsfs) are key regulators of plant responses to abiotic and biotic stressors. However, their role and mechanism of action in switchgrass have not been elucidated. Hence, this study aimed to identify the Hsf family in switchgrass and understand its functional role in heat stress signal transduction and heat tolerance by using bioinformatics and RT-PCR analysis. Forty-eight PvHsfs were identified and divided into three main classes based on their gene structure and phylogenetic relationships: HsfA, HsfB, and HsfC. The results of the bioinformatics analysis showed a DNA-binding domain (DBD) at the N-terminal in PvHsfs, and they were not evenly distributed on all chromosomes except for chromosomes 8 N and 8 K. Many cis-elements related to plant development, stress responses, and plant hormones were identified in the promoter sequence of each PvHsf. Segmental duplication is the primary force underlying Hsf family expansion in switchgrass. The results of the expression pattern of PvHsfs in response to heat stress showed that PvHsf03 and PvHsf25 might play critical roles in the early and late stages of switchgrass response to heat stress, respectively, and HsfB mainly showed a negative response to heat stress. Ectopic expression of PvHsf03 in Arabidopsis significantly increased the heat resistance of seedlings. Overall, our research lays a notable foundation for studying the regulatory network in response to deleterious environments and for further excavating tolerance genes in switchgrass.

Hydrogen Sulfide Alleviates Cadmium Stress by Enhancing Photosynthetic Efficiency and Regulating Sugar Metabolism in Wheat Seedlings.

Hydrogen sulfide (H2S) plays prominent multifunctional roles in the mediation of various physiological processes and stress responses to plants. In this study, hydroponic experiments were carried out to explore the effects of NaHS pretreatment on the growth of wheat (Triticum aestivum L.) under 50 μM cadmium (Cd). Compared with Cd treatment alone, 50 μM NaHS pretreatment increased the plant height, soluble sugar content of shoots and roots, and dry weight of shoots and roots under Cd stress, while the Cd concentration of shoots and roots was significantly reduced by 18.1% and 25.9%, respectively. Meanwhile, NaHS pretreatment protected the photosynthetic apparatus by increasing the net photosynthetic rate and PSII electron transportation rate of wheat leaves under Cd stress. NaHS pretreatment significantly increased the soluble sugar content to maintain the osmotic pressure balance of the leaf cells. The gene expression results associated with photosynthetic carbon assimilation and sucrose synthesis in wheat leaves suggested that the NaHS pretreatment significantly up-regulated the expression of TaRBCL, TaRBCS, and TaPRK, while it down-regulated the expression of TaFBA, TaSuSy, TaSAInv, and TaA/NInv. In summary, NaHS pretreatment improved the resistance of wheat seedlings under Cd stress by increasing the rate of photosynthesis and regulating the expression of genes related to sugar metabolism.

ZmAGO18b negatively regulates maize resistance against southern leaf blight.

Here, we report that ZmAGO18b encoding an argonaute protein is a negative regulator of maize resistance against southern leaf blight. Southern leaf blight caused by fungal pathogen Cochliobolus heterostrophus is a destructive disease on maize throughout the world. Argonaute (AGO) proteins, key regulators in small RNA pathway, play important roles in plant defense. But whether they have function in maize resistance against C. heterostrophus is unknown. Association analysis between the nucleic variation of 18 ZmAGO loci with disease phenotype against C. heterostrophus was performed, and the ZmAGO18b locus was identified to be associated with resistance against C. heterostrophus. Overexpression of ZmAGO18b gene suppresses maize resistance against C. heterostrophus, and mutation of ZmAGO18b enhances maize resistance against C. heterostrophus. Further, we identified the resistant haplotype of ZmAGO18b by association analysis of natural variation in ZmAGO18b genomic DNA sequences with seedling resistance phenotypes against C. heterostrophus and confirmed the resistant haplotype is co-segregated with resistance phenotypes against C. heterostrophus in two F2 populations. In sum, this study reports that ZmAGO18b negatively regulates maize resistance against C. heterostrophus.

Regulating drought tolerance in cotton by the expression of a specific allele of heat shock protein 70

Plant-specific heat shock protein 70 s (HSP70s) play crucial roles in response to various environmental stimuli. GhHSP70-26, an HSP70 member, is involved in the response to multiple abiotic stresses in cotton (Gossypium hirsutum). This study explored the relationship between the genetic diversity of GhHSP70–26 and drought resistance in cotton to aid crop breeding. Indel sites at −650 bp upstream of the GhHSP70–26 promoter were discovered in cotton and designated an M-650 marker. The M-650 marker was significantly associated with the effective boll numbers (M-650-In360 > M-650-Del) in 110 types of cotton under drought stress conditions for three years. The relative expression levels of GhHSP70–26 was linearly correlated with comprehensive drought resistance in cotton seedlings. The gene expression levels were enhanced in BC2F2(pGhHSP70–26In360) of cotton and the transgenic lines pGhHSP70–26In360:GhHSP70–26 of Arabidopsis, and drought resistance was also enhanced. After PEG, ABA and SA treatments, the transgenic lines of M-650-In360 promoter showed higher GUS expression activity than the M-650-del promoter in Arabidopsis. The GhFLZ, GhABF3, and GhRVE8 transcription factors could regulate to In360 bp of pGhHSP70–26 to activate high levels of gene expression. These results provide important genetic information to study the natural variation of drought tolerance in cotton, and the loci or exceptional promoters identified can be used as direct targets for cotton trait improvement and genetic engineering.

Identification of genes for leaf rust resistance in seedlings of wheat cultivars from the Yellow-Huai Basin in China and slow rusting observations in field trials

Wheat leaf rust is a devastating disease worldwide. Identification of leaf rust resistance genes in seedlings and of genes for slow rusting are important in resistance breeding and for gene deployment to control the disease. A total of 108 wheat cultivars from the Beijing and Shandong province and a set of 36 differentials, mostly near-isogenic lines in the background of Thatcher with known leaf rust resistance genes, were tested with 20 Puccinia triticina pathotypes (FHJS1, FGBQ,PGJQ, SHJT, FHGQ, PHTT1, FHGQ, FHGQ, PHJS, THSM, FHSQ, PHST, PRSQ, FNTQ, PHGM, KHGQ, PHTT2, TGTT, FHJS2, NHHT) at the seedling stage in the greenhouse. The cultivars and differentials were also planted in the field to test their slow rusting resistance using a mixture of races at Baoding, Hebei province and Zhoukou, Henan province, for two consecutive years. Ten leaf rust resistance genes, Lr1, 9, 10, 19, 20, 24, 26, 34, 37 and 46 were identified in the 57 commercial wheat cultivars, either singly or in combination, using molecular markers. Combined, the results from gene postulation and marker detection showed that one or more of the genes Lr1, 3, 10, 14a, 14b, 26, 36, 39, 34 and 46, were present in 57 cultivars, and that no known resistance gene was present in the remaining 51 cultivars. The resistance gene Lr26 was present in 42 cultivars, and nine cultivars contained Lr1. Lr46 was present in 10 cultivars, as indicated by the presence of the closely linked marker csLV46G22. Seven genotypes were identified as possibly carrying the gene Lr39. Lr3 and 10 were found in six and four genotypes, respectively. The ggenes Lr14b and 34 were each present in three cultivars, while evidence for the presence of Lr14a and 36 was obtained in single genotypes. Finally, 12 cultivars showed slow rusting resistance at two locations in two crop seasons. The identification of leaf rust resistance genes in Chinese wheat cultivars will be helpful for gene deployment to control leaf rust.

Identification of Novel QTLs/Defense Genes in Spring Wheat Germplasm Panel for Seedling and Adult Plant Resistance to Stem Rust and Their Validation Through KASP Marker Assays.

Stem rust is one of the major diseases threatening wheat production globally. To identify novel resistance quantitative trait loci (QTLs), we performed 35K Axiom Array SNP genotyping assays on an association mapping panel of 400 germplasm accessions, including Indian landraces, in conjunction with phenotyping for stem rust at seedling and adult plant stages. Association analyses using three genome wide association study (GWAS) models (CMLM, MLMM, and FarmCPU) revealed 20 reliable QTLs for seedling and adult plant resistance. Among these 20 QTLs, five QTLs were found consistent with three models, i.e., four QTLs on chromosome 2AL, 2BL, 2DL, and 3BL for seedling resistance and one QTL on chromosome 7DS for adult plant resistance. Further, we identified a total of 21 potential candidate genes underlying QTLs using gene ontology analysis, including a leucine rich repeat receptor (LRR) and P-loop nucleoside triphosphate hydrolase, which have a role in pathogen recognition and disease resistance. Furthermore, four QTLs (Qsr.nbpgr-3B_11, QSr.nbpgr-6AS_11, QSr.nbpgr-2AL_117-6, and QSr.nbpgr-7BS_APR) were validated through KASP located on chromosomes 3B, 6A, 2A, and 7B. Out of these QTLs, QSr.nbpgr-7BS_APR was identified as a novel QTL for stem rust resistance which has been found effective in both seedling as well as the adult plant stages. Identified novel genomic regions and validated QTLs have the potential to be deployed in wheat improvement programs to develop disease resistant varieties for stem rust and can diversify the genetic basis of resistance.

Major Susceptibility Gene Epistasis over Minor Gene Resistance to Spot Form Net Blotch in a Commercial Barley Cultivar.

Spot form net blotch, caused by Pyrenophora teres f. maculata, is a significant global disease of barley (Hordeum vulgare). Baudin, a barley cultivar that was until recently extensively grown in Western Australia, was reported as having minor seedling resistance. However, Baudin was highly susceptible to a local isolate, M3, suggesting that this isolate had gained virulence against a major susceptibility gene. M3 causes atypical lesions with pale centers early in the infection, with initial screens of a segregating population indicating that this was determined by a single locus in the Baudin genome. The susceptibility was semidominant in F1 progeny and the susceptibility gene, designated Spm1 (Susceptibility to P. teres f. maculata 1), mapped to a 190-kb section of the resistance gene-rich Mla region of chromosome 1H. Phenotyping with Ptm SP1, a non-M3 pathotype, identified a seedling resistance locus on 2H. Minor gene resistance is generally regarded as potentially durable, but our findings suggest the resistance to spot form net blotch in Baudin is nullified by strong susceptibility conferred by a separate locus on 1H. [Formula: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Morphology of Oil Palm (Elaeis guineensis Jacq.) Seedlings Under Drought Stress with Oil Palm Shell Ash and Aspergillus niger treatment

Climate change is a limiting factor that contributes to weather anomalies such as varying rainfall intensity. Weather abnormalities impact plantation crops, such as oil palm, which are very sensitive to water deficits, and inhibition of growth in the nursery phase reduces seed quality. In an effort to increase the resistance of oil palm seedlings to drought stress, palm shell ash is given because it contains high silicon (Si) ranging from 43% to 63%. Furthermore, the fungus Aspergillus niger is known to decompose and release insoluble silicon into orthosilicic acid into the soil solution, which can be absorbed by plants, This study used randomized block design with two factors drought stress factor with four level field capacity (FC) of 80%, 60%, 40% dan 20%; factor palm oil shell and Aspergillus niger 0, 10, 20, 30 g + 5 ml/polybag. The results showed that the parameter number of Aspergillus niger colonies before and after the drought stress treatment decreased, drought stress was also a significant difference in the parameters of plant height and number of leaves, while the treatment of oil palm shell ash with the addition of Aspergillus niger had no significant effect on plant height parameters and number of leaves of oil palm seedlings.

Control Efficacy of Jingdusha against Corynespora cassiicola (Hyphomycetales: Dematiaceae) on Cucumber

Aims: The paper aimed to clarify the effect of cucumber target leaf spot (TLS) under the Jingdusha (JDS) treatment.
 Study Design: We applied the method of artificial inoculation in the pot, and analyzed the changes in growth indexes and physiological characteristics.
 Place and Duration of Study: In 2018, these experiments were conducted in College of Bioscience and Biotechnology of Shenyang Agricultural University (Lab 240).
 Methodology: The seedlings in the two-leaf period were induced by the best application scheme of JDS, then inoculated Corynespora cassiicola for 24 h. Cucumber seedlings of each treatment group were randomly selected for photographing and growth index determination after inoculation for 5 d. The leaves of cucumber seedlings in each treatment group were randomly collected at 1 d, 3 d, 5 d, 7 d, and 9 d after inoculation for the determination of physiological and biochemical indicators.
 Results: When C. cassiicola infects cucumber, JDS can effectively improve the growth and photosynthetic pigment content of cucumber, reduce the degradation of chlorophyll (Chl) under the stress of C. cassiicola, strengthen the variety of metabolic responses in the plant, repair the enzyme protection system of cucumber leaves, reduce the accumulation of reactive oxygen species, shorten the process of membrane lipid peroxidation in blades.
 Conclusion: Taken together, these results suggest that JDS can improve the resistance of cucumber seedlings to C. cassiicola by regulating growth indexes and physiological characteristics. This work will provide a theoretical basis for further elucidating the molecular mechanism of JDS in cucumber defense against C. cassiicola.

Spermidine and Spermine Converted from Putrescine Improve the Resistance of Wheat Seedlings to Osmotic Stress

Spermidine and Spermine Converted from Putrescine Improve the Resistance of Wheat Seedlings to Osmotic Stress

Seaweed fertilizer improved drought tolerance of tomato seedlings in sandy soil

Global climate change has increased atmospheric transpiration and evaporation and decreased rainfall, and these changes have exacerbated water deficit-induced restrictions on agricultural production in arid and semi-arid areas. To test the influence of seaweed fertilization, a product of Qingdao Bright Moon Seaweed Group Co., Ltd®., on tomato drought response in sandy soils, on tomato drought response in sandy soils, a pot experiment was conducted in a greenhouse to measure biomass and leaf parameters, including chlorophyll concentration, relative water content, and carbohydrate and nitrogen content, under two water-availability scenarios including 85 ± 5% field water content and without irrigating treatment (chemical fertilization under well-watered conditions (WW), chemical fertilization under drought-stressed conditions (WD), seaweed fertilization under well-watered conditions (WW + SF), and seaweed fertilization under drought-stressed conditions (WD + SF)). The results showed that under water deficit stress, seaweed fertilization increased soil urease activity (429%) and soil ammonium nitrogen content, thereby increasing the nitrogen content available to the plants. Seaweed fertilization also enhanced the leaf proline content and water content of the plants, and decreased oxidative damage (low malondialdehyde content, which is lower 43.8% compared with WD). In addition, seaweed fertilization increased the leaf nitrogen content and reduced the nonstructural carbohydrate contentto maintain a relatively low total nonstructural carbohydrate/nitrogen (C/N) ratio. Taken together, seaweed fertilization-induced changes improved drought resistance in tomato seedlings and these results suggested that seaweed fertilization has the potential to improve crop drought resistance in sandy areas.

Validation of an alternative small stem assay for blight resistance in backcross hybrid chestnuts (Castanea spp.) and recommendations for its expanded use.

We evaluated an alternative small stem assay (AltSSA) for blight resistance in backcross hybrid chestnuts (Castanea dentata/mollissima). Whereas standard small stem assays (SSAs) are done by inoculating small incisions in stems, in our AltSSA, 4 to 5 mm stems are cut off, and the exposed (living) stem tips are inoculated with discs of Cryphonectria parasitica inoculum and temporarily covered with plastic sleeves. Intended primarily for forward selection, this method was designed to be easy to implement, to consistently induce cankering, and to better enable seedling recovery via the development of lateral shoots from the lower stem. After 90+ days, cankers are evaluated and removed, and seedlings are prepared for out-planting. Previous results showed that AltSSAs performed at least as well as a common SSA method in distinguishing resistant and susceptible types. In this follow-up analysis of 35 lines of backcross seedlings studied in 2020 and 2021, we show that mean orange zone canker length (OZCL) and a multifactor PCA-based blight resistance index gave results consistent with predictions derived from the blight resistance phenotype (two methods) and percent American chestnut ancestry of the parents of each line. As expected, based upon the apparent polygenic inheritance of blight resistance in backcross chestnuts, mean OZCL of backcross families ranged from intermediate (F1-level) to low (American chestnut-level). Consistent with prior results, canker production was near 100%, survivorship after out-planting was very high, and post-inoculation deaths were apparently unrelated to the stem tip inoculations (e.g., unrelated basal cankering). Altogether, these results suggest that the AltSSA is a viable method for early detection of relative blight resistance in seedlings and may enable a reduction in the numbers of trees out-planted and placed under care for long-term evaluation and breeding.

Simplified extraction protocol for plant tissues and reverse transcription RPA assay for quick and reliable diagnosis and its application in resistance screening of chilli veinal mottle virus

The widespread occurrence and predominant association of chilli veinal mottle virus (ChiVMV) with the valuable chilli landraces of North East Region (NER) of India and associated threat to chilli production necessitated the development of simplified and robust detection procedure. Present study reports a simplified reverse transcription-recombinase polymerase amplification (RT-RPA) method for detection of ChiVMV in crude leaf extract prepared through simplified extraction protocol using NaOH:EDTA (1:1) based tissue lysis, without the need of conventional RNA extraction and sample processing. Developed RT-RPA assay could be performed at an isothermal temperature (38 °C) in 30 min and exhibited no cross-reactivity with other prevalent chilli viruses (potato virus Y, cucumber mosaic virus, large cardamom chirke virus, capsicum chlorosis orthotospovirus, pepper mild mottle virus and chilli leaf curl virus), indicating high specificity. It could detect ChiVMV up to 10−9 dilution (100 ag/μl) of crude leaf extract, 10 ag/μl of RNA of ChiVMV infected leaf tissues and plasmid DNA containing viral gene insert, thus exhibiting sufficient sensitivity which is at par or better than the standard RT-PCR. Developed RT-RPA assay was employed to reveal the widespread occurrence of ChiVMV in NER India with 50.81% (1545 samples tested) of symptomatic and 7.85% (1593 samples tested) of asymptomatic samples tested positive. RT-RPA exhibited higher sensitivity in detection of ChiVMV infection in field samples as compared to the standard RT-PCR which gave false negative in 2.07% of symptomatic and 2.01% of asymptomatic samples. The developed assay was further applied in screening of 49 chilli germplasm for ChiVMV infection. The pooled results of field screening based on the disease score indicated that none of the chilli germplasm had immune or complete resistance, while 29 chilli germplasm (bird's eye chilli: C. frutescens; Morokatekpa: C. annuum, Leihao morok, Morok masingkha; Chingpimorok: Capsicum sp.) exhibited tolerant reaction with a disease score of 1.27–2.00. All the tested bird's eye chilli germplasm showed tolerance to the ChiVMV. The artificial screening to the severe isolate and qRT-PCR based viral titre determination confirmed the results of field screening wherein the germplasm RCMC6, RCMC7, RCMC17, RCMC27 and RCMC42 exhibited either asymptomatic or mild mosaic symptoms and decrease in viral titre at 20 DAI thus categorized as tolerant. The simplified RT-RPA assay developed and validated in the present study can be applied in routine detection of ChiVMV in field samples, disease-free seedling production and resistance screening under resource poor laboratory setup with limited technical expertise. Chilli germplasm with tolerance to ChiVMV identified in the present study can be used as donors in resistance breeding.

Novel genomic regions on chromosome 5B controlling wheat powdery mildew seedling resistance under Egyptian conditions.

Wheat powdery mildew (PM) causes significant yield losses worldwide. None of the Egyptian wheat cultivars was detected to be highly resistant to such a severe disease. Therefore, a diverse spring wheat panel was evaluated for PM seedling resistance using different Bgt conidiospores collected from Egyptian fields in two growing seasons. The evaluation was done in two separate experiments. Highly significant differences were found between the two experiments suggesting the presence of different isolates populations. Highly significant differences were found among the tested genotypes confirming the ability to improve PM resistance using the recent panel. Genome-wide association study (GWAS) was done for each experiment separately and a total of 71 significant markers located within 36 gene models were identified. The majority of these markers are located on chromosome 5B. Haplotype block analysis identified seven blocks containing the significant markers on chromosome 5B. Five gene models were identified on the short arm of the chromosome. Gene enrichment analysis identified five and seven pathways based on the biological process and molecular functions respectively for the detected gene models. All these pathways are associated with disease resistance in wheat. The genomic regions on 5B seem to be novel regions that are associated with PM resistance under Egyptian conditions. Selection of superior genotypes was done and Grecian genotypes seem to be a good source for improving PM resistance under Egyptian conditions.

A Review of Propagation and Restoration Techniques for American Beech and Their Current and Future Application in Mitigation of Beech Bark Disease

The American beech (Fagus grandifolia Ehrh.) has been impacted by the beech bark disease (BBD) complex throughout the northeastern United States for over 100 years, but the disease has been present in the Great Lakes region only for around 20 years, requiring acknowledgement of the evolving context surrounding F. grandifolia. This disease threatens to remove a foundational tree species which is especially important ecologically for wildlife habitat and mast, and as a climax successional species. We review advances in propagation techniques of F. grandifolia with the goal of addressing their use in the rehabilitative restoration of forests affected by BBD. Natural regeneration and artificial methods of propagation are addressed, along with how they may be applied for mitigation. Silvicultural interventions are discussed that may be necessary to protect and release resistant seedlings to promote persistence. An existing framework is used to explore context necessary for decision making in restoration. Nucleated seed orchards of resistant trees may currently be the most effective and practical method for introduction of BBD-resistant F. grandifolia into affected northern hardwood forests.

Effects of 5-HT on the cold resistance of mangrove Kandelia obovata seedlings.

5-hydroxytryptamine (5-HT) participates in plant growth and development, and can also delay senescence and cope with abiotic stress. To explore the role of 5-HT in regulating the abilities of mangrove in cold resis-tance, we examined the effects of cold acclimation and the spraying of p-chlorophenylalanine (p-CPA, 5-HT synthesis inhibitor) on leaf gas exchange parameters and CO2 response curves (A/Ca), as well as the endogenous phytohormone content levels in the mangrove species Kandelia obovata seedlings under low temperature stress. The results showed that low temperature stress significantly reduced the contents of 5-HT, chlorophyll, endogenous auxin (IAA), gibberellin (GA), and abscisic acid (ABA). It weakened the CO2 utilization abilities of plants and reduced net photosynthetic rate, which ultimately reduced carboxylation efficiency (CE). Under low temperature stress, exogenous p-CPA reduced the contents of photosynthetic pigments, endogenous hormones, and 5-HT in the leaves, which aggravated the damages caused by low temperature stress on photosynthesis. By enhancing cold acclimation abilities, the endogenous IAA content in the leaves could was reduced under low temperature stress, promoted the production of 5-HT, improved the contents of photosynthetic pigments, GA, and ABA, as well as enhanced photosynthetic carbon assimilation abilities, which would increase photosynthesis in the K. obovata seedlings. Under cold acclimation conditions, the spraying of p-CPA could significantly inhibit the synthesis of 5-HT, promote the production of IAA, and reduce the contents of photosynthetic pigments, GA, ABA, and CE, which would weaken the effects of cold acclimation by improving the cold resistance of mangroves. In conclusion, cold acclimation could improve the cold resistance abilities of K. obovata seedlings by regulating photosynthetic carbon assimilation capacity and the contents of endogenous phytohormone. 5-HT synthesis is one of the necessary conditions for improving the cold resistance abilities of mangroves.

Heterogeneous expression of stearoyl-acyl carrier protein desaturase genes SAD1 and SAD2 from Linum usitatissimum enhances seed oleic acid accumulation and seedling cold and drought tolerance in Brassica napus

Flax (Linum usitatissimum L.) is a versatile crop and its seeds are a major source of unsaturated fatty acids. Stearoyl-acyl carrier protein desaturase (SAD) is a dehydrogenase enzyme that plays a key role in oleic acid biosynthesis as well as responses to biotic and abiotic stresses. However, the function of SAD orthologs from L. usitatissimum has not been assessed. Here, we found that two LuSAD genes, LuSAD1 and LuSAD2, are present in the genome of L. usitatissimum cultivar ‘Longya 10’. Heterogeneous expression of either LuSAD1 or LuSAD2 in Arabidopsis thaliana resulted in higher contents of total fatty acids and oleic acid in the seeds. Interestingly, ectopic expression of LuSAD2 in A. thaliana caused altered plant architecture. Similarly, the overexpression of either LuSAD1 or LuSAD2 in Brassica napus also resulted in increased contents of total fatty acids and oleic acid in the seeds. Furthermore, we demonstrated that either LuSAD1 or LuSAD2 enhances seedling resistance to cold and drought stresses by improving antioxidant enzyme activity and nonenzymatic antioxidant levels, as well as reducing membrane damage. These findings not only broaden our knowledge of the LuSAD functions in plants, but also offer promising targets for improving the quantity and quality of oil, and the abiotic stress tolerance of oil-producing crops, through molecular manipulation.

Indices of antioxidant and osmoprotective systems in seedlings of winter wheat cultivars with different frost resistance

The functioning of the stress-protective systems of wheat under the action of cold at the early stages of plant development remains poorly studied. The aim of this work was a comparative study of antioxidant activity and the content of sugars and proline as indicators of osmoprotective activity during cold adaptation of seedlings of seven winter bread wheat (Triticum aestivum L.) cultivars that differ significantly in frost resistance. The 3-day-old etiolated seedlings were hardened at 2°C for 6 days and then frozen for 5 h at -6 or -9°C. Two days after freezing, the survival of seedlings was assessed by their ability to grow. A decrease in ROS content, an increase in the activity of antioxidant enzymes catalase and guaiacol peroxidase and accumulation of sugars in the shoots of high-frost-resistant cultivars during hardening were detected. The absolute values of catalase and guaiacol peroxidase activity correlated positively with the frost resistance of seedlings. The negative correlation between the frost tolerance of the cultivars and the accumulation of proline in the seedlings during hardening was recorded. The possibility of using the studied biochemical indices for frost resistance screening of winter wheat varieties at the seedling stage was stated. Keywords: antioxidant system, cold hardening, frost resistance, osmolytes, oxidative stress, Triticum aestivum

Effective sources of powdery mildew resistance among spring bread wheat for the northwest of the russian federation

Background. Bread wheat (Triticum aestivum L.) is one of the world’s main food crops. In Russia, its gross harvest in recent years has reached 21.079 million tons. Blumeria graminis is one of the most harmful diseases of bread wheat. Annual harvest losses can reach 10–30%. In Leningrad Province, powdery mildew appears almost every year on cereals. Development of cultivars resistant to powdery mildew is the most important trend in spring bread wheat breeding. Its progress is determined by new sources of effective resistance genes and their incorporation into promising spring bread wheat cultivars. The purpose of this work was to retest the seedling and adult resistance to powdery mildew in spring bread wheat accessions selected over a period of more than twenty years and redefine the effectiveness of disease resistance sources at the present time.Materials and methods. Since 2000, VIR has conducted a search for powdery mildew resistance among 1283 spring bread wheat accessions. The identified 36 sources of adult and seedling powdery mildew resistance were reevaluated in 2022. Field and laboratory studies into the resistance to the pathogen were performed according to VIR’s guidelines.Results and discussion. In 2022, field and laboratory studies of spring bread wheat cultivars revealed accessions with resistance to the pathogen in all phases of plant development. Six sources remained resistant to powdery mildew for 13–22 years, another six showed resistance for 7–12 years, and 8 cultivars were immune for 6 years. Resistance of 9 accessions identified for this trait in 2020 was confirmed.Conclusion. Field and laboratory research into the resistance of spring bread wheat accessions to the pathogen identified sources retaining seedling and adult resistance to the Leningrad population of powdery mildew for 7 years or more. These accessions are recommended for use in wheat breeding programs.

Effect of Ectomycorrhizal Fungi on the Drought Resistance of Pinus massoniana Seedlings.

Studies on the dynamics of non-structural carbohydrates (NSCs) play an important role in understanding the mechanisms of plant responses to drought stress. The objective of this study was to assess the influence of ectomycorrhizal fungi (ECMF) on the content and distribution of NSCs in Pinus massoniana seedlings under different drought intensities and to further explore the possible mechanism by which ECMF enhances the stress resistance of host plants. We conducted a pot experiment using P. massoniana seedlings that were inoculated (M) or non-inoculated (NM) with Suillus luteus (Sl) under well-watered, moderate, and severe drought stress conditions. The results showed that drought significantly reduced the photosynthetic capacity of P. massoniana seedlings and inhibited their growth rate. P. massoniana could respond to different degrees of drought stress by increasing the accumulation of NSCs and increasing WUE. However, compared with well-watered treatment, NSCs consumption began to appear in the roots of NM due to the decrease in starch content under severe drought, whereas NSCs content in M seedlings was higher than that in the well-watered treatment, showing that the ability to maintain C balance was higher in M seedlings. Compared with NM, inoculation with Sl increased the growth rate and biomass of roots, stems, and leaves under moderate and severe drought. In addition, Sl can also improve the gas exchange parameters (net photosynthetic rate, transpiration rate, intercellular CO2 concentration and stomatal conductance) of P. massoniana seedlings compared with NM seedlings, which was conducive to the hydraulic regulation of seedlings and improved their C fixation capacity. Meanwhile, the content of NSCs in M seedlings was higher. Moreover, the soluble sugar content and SS/St ratio of leaves, roots, and whole plants were higher under drought stress after Sl inoculation, indicating that Sl could also change the C distribution mode, regulate more soluble sugar to respond to drought stress, which was conducive to improving the osmotic adjustment ability of seedlings, and providing more available C sources for plant growth and defense. Overall, inoculation with Sl could enhance the drought resistance of seedlings and promote their growth under drought stress by improving NSCs storage, increasing soluble sugar distribution, and improving the plant water balance of P. massoniana seedlings.