Poplar Varieties Research Articles

MiRNAs profiles among three poplar varieties provide insights into different molecular responses in resistance to newly emerging bacterial pathogen.

Canker caused by Lonsdalea populi has seriously reduced the economic and ecological benefits of poplar. MicroRNAs play vital roles in the response of plants to biotic stress. However, there is little research about the regulatory mechanism of miRNAs among different tree varieties upon pathogen infection. To dissect miRNAs involved in L. populi resistance, three poplar varieties, 2025 (susceptible), 107 (moderately resistant) and Populus. tomentosa cv 'henan' (resistant) were selected to elucidate the expression profiles of miRNAs using small RNA-seq. A total of 227 miRNAs were identified from all varieties. Intriguingly, miR160, miR169, miR171 and miR482b-5p were only identified in the resistant variety P. tomentosa upon pathogen infection, and these miRNAs might be important candidates for future investigation to improve the tolerance of poplar to L. populi. Among all identified miRNAs, 174 were differentially expressed in all varieties. Functional annotation analysis indicated that an array of miRNAs, including miR482, miR472, miR169, miR481, and miR172, should be involved in disease resistance and phytohormone signal transduction. Furthermore, correlation analysis of small RNA-seq and RNA-seq identified a handful of L. populi-responsive miRNAs and target genes, which exhibited that miR159 and miR172 played key roles in resistant variety P. tomentosa by targeting MYB and ERF, while miR6462c-5p and miR828 were related to the susceptibility of 2025 by targeting MYB. The comprehensive integration analysis in this research provides new insights into the regulatory pathways involved in the defence response of poplar to L. populi and offers crucial candidate miRNAs-target genes modules for poplar resistance improvement.

Multi-omics analysis of Populus simonii × P. nigra leaves under Hyphantria cunea stress.

Poplar is an important greening and timber tree species in China, which has great economic and ecological values. However, the spread of Hyphantria cunea has become increasingly serious in recent years, resulting in huge economic loss of poplar production. Exploring the molecular mechanism of poplar reponse to H. cunea stress has significant implications for future development of new insect-resistant poplar varieties using genetic engineering technology. In this study, a total of 1039 differentially expressed genes (DEGs), 106 differentially expressed proteins (DEPs) and 212 differentially expressed metabolites (DEMs) were screened from Populus simonii × P. nigra leaves under H. cunea stress by transcriptome, proteomics and metabolomics analysis, respectively. GO and KEGG analysis showed that the DEGs and DEPs are associated with endopeptidase inhibitor activity, stress response, α-linolenic acid metabolism, phenylpropanoid biosynthesis and metabolic pathways, cysteine and methionine metabolism pathways and MAKP signaling pathway. Metabolomics analysis showed the most of DEMs were lipids and lipid molecules, and the pathways associated with transcriptome mainly include plant hormone signal transduction, α-linolenic acid metabolic pathway, amino sugar and nucleotide sugar metabolism, and phenylpropanoid biosynthesis. In particular, multi-omics analysis showed that several pathways such as α-linolenic acid metabolic, phenylpropanoid biosynthesis and metabolic pathway and cysteine and methionine metabolic pathway were significantly enriched in the three omics, which may play an important role in the resistance to pests in poplar.

PdPLR1 effectively enhances resistance of Populus deltoides ‘shalinyang’ to Anoplophora glabripennis by positive regulation of lignan synthesis

Anoplophora glabripennis (ALB) is one of the most devastating wood boring insects of poplars. Populus deltoides ‘Shalinyang (PdS), a new poplar variety, shows strong resistance to ALB infestation. However, the molecular mechanism of insect resistance in PdS is unclear. Here, we found that lignan content was much higher in PdS phloem after ALB infestation than in healthy trees, and that adding lignan to artificial diet significantly reduced: larval weight; digestive enzyme activity (cellulase [CL], polygalacturonase [PG]); detoxification enzyme activity (carboxylesterase [CarE], glutathione S-transferase [GSH-ST]); and defense enzyme activity (Catalase [CAT]). We further identified the lignan biosynthesis-related PdPLR1 gene (Pinoresinol-lariciresinol reductase, PLR) based on transcriptome analysis, and it was significantly up-regulated in the PdS phloem attacked by ALB. Overexpression of PdPLR1 in Arabidopsis increased th lignan content. In contrast, silencing PdPLR1 in PdS significantly decreased expression levels of PdPLR1 and lignan content by 82.45% and 56.85%. However, silencing PdPLR1 increased the number of adults ovipositions and eggs hatching. The activity of CL, PG, CarE, GSH-ST and CAT and the biomass of larvae fed on phloem of PdS with silenced PdPLR1 were significantly higher than in the control. Taken together, up regulation of PdPLR1 enhanced PdS resistance to ALB by regulating lignan synthesis. Our findings provide in-depth insights into the molecular mechanisms of PdS-ALB interactions, which lay the foundation for understanding of defense in poplars to pest infection.

PagEXPA1 combines with PagCDKB2;1 to regulate plant growth and the elongation of fibers in Populus alba × Populus glandulosa

Expansins are important plant cell wall proteins. They can loosen and soften the cell walls and lead to wall extension and cell expansion. To investigate their role in wood formation and fiber elongation, the PagEXPA1 that highly expressed in cell differentiation and expansion tissues was cloned from 84K poplar (Populus alba × P. glandulosa). The subcellular localization showed that PagEXPA1 located in the cell wall and it was highly expressed in primary stems and young leaves. Compared with non-transgenic 84K poplar, overexpression of PagEXPA1 can promote plant-growth, lignification, and fiber cell elongation, while PagEXPA1 Cas9-editing mutant lines exhibited the opposite phenotype. Transcriptome analysis revealed that DEGs were mainly enriched in some important processes, which are associated with cell wall formation and cellulose synthesis. The protein interaction prediction and expression analysis showed that PagCDKB2:1 and PagEXPA1 might have an interaction relationship. The luciferase complementary assay and bimolecular fluorescence complementary assay validated that PagEXPA1 can combined with PagCDKB2;1. So they promoted the expansion of xylem vascular tissues and the development of poplar though participating in the regulation of cell division and differentiation by programming the cell-cycle. It provides good foundation for molecular breeding of fast-growing and high-quality poplar varieties.

Phenotyping of Drought-Stressed Poplar Saplings Using Exemplar-Based Data Generation and Leaf-Level Structural Analysis.

Drought stress is one of the main threats to poplar plant growth and has a negative impact on plant yield. Currently, high-throughput plant phenotyping has been widely studied as a rapid and nondestructive tool for analyzing the growth status of plants, such as water and nutrient content. In this study, a combination of computer vision and deep learning was used for drought-stressed poplar sapling phenotyping. Four varieties of poplar saplings were cultivated, and 5 different irrigation treatments were applied. Color images of the plant samples were captured for analysis. Two tasks, including leaf posture calculation and drought stress identification, were conducted. First, instance segmentation was used to extract the regions of the leaf, petiole, and midvein. A dataset augmentation method was created for reducing manual annotation costs. The horizontal angles of the fitted lines of the petiole and midvein were calculated for leaf posture digitization. Second, multitask learning models were proposed for simultaneously determining the stress level and poplar variety. The mean absolute errors of the angle calculations were 10.7° and 8.2° for the petiole and midvein, respectively. Drought stress increased the horizontal angle of leaves. Moreover, using raw images as the input, the multitask MobileNet achieved the highest accuracy (99% for variety identification and 76% for stress level classification), outperforming widely used single-task deep learning models (stress level classification accuracies of <70% on the prediction dataset). The plant phenotyping methods presented in this study could be further used for drought-stress-resistant poplar plant screening and precise irrigation decision-making.

PagSOD2a improves poplar salt tolerance by elevating superoxide dismutase activity and decreasing malondialdehyde contents.

Superoxide dismutase (SOD) is widely present in plants and plays a crucial role in defending against oxidative stress and preventing tissue damage. This study discovered that the PagSOD2a gene in 84K poplar (Populus alba × P. glandulosa) exhibits a distinct capacity to be induced in response to salt stress. To delve into the pivotal role of PagSOD2a in conferring salt tolerance, the entire PagSOD2a fragment was successfully cloned from 84K poplar and the potential function of PagSOD2a was explored using bioinformatics and subcellular localization. PagSOD2a was found to encode a CuZn-SOD protein localized in chloroplasts. Furthermore, six CuZn-SOD family members were identified in poplar, with closely related members displaying similar gene structures, indicating evolutionary conservation. Morphological and physiological indexes of transgenic 84K poplar overexpressing PagSOD2a (OE) were compared with non-transgenic wild-type (WT) plants under salt stress. The OE lines (OE1 and OE3) showed improved growth performance, characterized by increased plant height and fresh weight, along with reduced malondialdehyde (MDA) content and electrolyte leakage rate under salt stress. Meanwhile, overexpression of PagSOD2a significantly augmented CuZn-SOD and total SOD enzyme activities, leading to a reduction in superoxide anion accumulation and an enhancement of salt tolerance. Additionally, co-expression and multilayered hierarchical gene regulatory network (ML-hGRN) mediated by PagSOD2a constructed using transcriptome data revealed that PagSOD2a gene may be directly regulated by SPL13, NGA1b and FRS5, as well as indirectly regulated by MYB102 and WRKY6, in response to salt stress. These findings provide a theoretical and material foundation for further elucidating the function of PagSOD2a under salt stress and for developing salt-tolerant poplar varieties.

Metabolome combined with transcriptome profiling reveals the dynamic changes in flavonoids in red and green leaves of Populus × euramericana 'Zhonghuahongye'.

Flavonoids are secondary metabolites that have economic value and are essential for health. Poplar is a model perennial woody tree that is often used to study the regulatory mechanisms of flavonoid synthesis. We used a poplar bud mutant, the red leaf poplar variety 2025 (Populus × euramericana 'Zhonghuahongye'), and green leaves as study materials and selected three stages of leaf color changes for evaluation. Phenotypic and biochemical analyses showed that the total flavonoid, polyphenol, and anthocyanin contents of red leaves were higher than those of green leaves in the first stage, and the young and tender leaves of the red leaf variety had higher antioxidant activity. The analyses of widely targeted metabolites identified a total of 273 flavonoid metabolites (114 flavones, 41 flavonols, 34 flavonoids, 25 flavanones, 21 anthocyanins, 18 polyphenols, 15 isoflavones, and 5 proanthocyanidins). The greatest difference among the metabolites was found in the first stage. Most flavonoids accumulated in red leaves, and eight anthocyanin compounds contributed to red leaf coloration. A comprehensive metabolomic analysis based on RNA-seq showed that most genes in the flavonoid and anthocyanin biosynthetic pathways were differentially expressed in the two types of leaves. The flavonoid synthesis genes CHS (chalcone synthase gene), FLS (flavonol synthase gene), ANS (anthocyanidin synthase gene), and proanthocyanidin synthesis gene LAR (leucoanthocyanidin reductase gene) might play key roles in the differences in flavonoid metabolism. A correlation analysis of core metabolites and genes revealed several candidate regulators of flavonoid and anthocyanin biosynthesis, including five MYB (MYB domain), three bHLH (basic helix-loop-helix), and HY5 (elongated hypocotyl 5) transcription factors. This study provides a reference for the identification and utilization of flavonoid bioactive components in red-leaf poplar and improves the understanding of the differences in metabolism and gene expression between red and green leaves at different developmental stages.

Three-Dimensional Quantification and Visualization of Leaf Chlorophyll Content in Poplar Saplings under Drought Using SFM-MVS

As global temperatures warm, drought reduces plant yields and is one of the most serious abiotic stresses causing plant losses. The early identification of plant drought is of great significance for making improvement decisions in advance. Chlorophyll is closely related to plant photosynthesis and nutritional status. By tracking the changes in chlorophyll between plant strains, we can identify the impact of drought on a plant’s physiological status, efficiently adjust the plant’s ecosystem adaptability, and achieve optimization of planting management strategies and resource utilization efficiency. Plant three-dimensional reconstruction and three-dimensional character description are current research hot spots in the development of phenomics, which can three-dimensionally reveal the impact of drought on plant structure and physiological phenotypes. This article obtains visible light multi-view images of four poplar varieties before and after drought. Machine learning algorithms were used to establish the regression models between color vegetation indices and chlorophyll content. The model, based on the partial least squares regression (PLSR), reached the best performance, with an R2 of 0.711. The SFM-MVS algorithm was used to reconstruct the plant’s three-dimensional point cloud and perform color correction, point cloud noise reduction, and morphological calibration. The trained PLSR chlorophyll prediction model was combined with the point cloud color information, and the point cloud color was re-rendered to achieve three-dimensional digitization of plant chlorophyll content. Experimental research found that under natural growth conditions, the chlorophyll content of poplar trees showed a gradient distribution state with gradually increasing values from top to bottom; after being given a short period of mild drought stress, the chlorophyll content accumulated. Compared with the value before stress, it has improved, but no longer presents a gradient distribution state. At the same time, after severe drought stress, the chlorophyll value decreased as a whole, and the lower leaves began to turn yellow, wilt and fall off; when the stress intensity was consistent with the duration, the effect of drought on the chlorophyll value was 895 &lt; SY-1 &lt; 110 &lt; 3804. This research provides an effective tool for in-depth understanding of the mechanisms and physiological responses of plants to environmental stress. It is of great significance for improving agricultural and forestry production and protecting the ecological environment. It also provides decision-making for solving plant drought problems caused by global climate change.

Influence of the type of planting material on the efficiency of establishment of poplar plantations in the Right Bank Forest Steppe

Purpose. To determine the features of the cultivation of energy plantation of poplar variety ‘Robusta’ on leached chernozems in the Central Forest Steppe of Ukraine.&#x0D; Methods. Field, laboratory, statistical.&#x0D; Results. Climatic changes actualize the need for the transition of agrarian business of Ukraine to agroforestry systems not only in the Steppe, but also in more northern regions of the country. The purpose of the research was to study the features of establishing poplar (Populus × euramericana) field protection plantations in the Central Forest Steppe of Ukraine. It was established that an effective way to increase the survival rate of one-year cutting seedlings of poplar varieties ‘Dorskamp’, ‘Robusta’ and ‘I‑45/51’ is to plant them without trunks. In all studied varieties, during the first two years, the survival of seedlings was higher in the version without a trunk and ranged from 57.0 to 68.9%, while in seedlings with a trunk it ranged from 50.3% to 68.1%. In 2022, due to irrigation, the survival rate was from 74.4% to 88.9%. The average height was also higher in plants grown from seedlings without a trunk. It turned out to be the highest in plants of the ‘Dorskamp’ clone, ranging from 188.6 to 209.3 cm. In uncutted plants of this variety, it was from 174.0 to 197.2 cm. It is advisable to continue the research started with the aim of breeding new forms of poplar and improving the technologies of creating forest and field plantations with the use of the varieties which can be used in the Polissia and Forest Steppe zones.

A WRKY transcription factor, PyWRKY71, increased the activities of antioxidant enzymes and promoted the accumulation of cadmium in poplar

Cadmium (Cd) pollution poses significant threats to the ecological environment and human health. Currently, phytoremediation is recognized as an environmentally friendly approach for mitigating Cd pollution, with increasing attention on the utilization of transgenic plants in Cd-contaminated soil remediation. In this study, we isolated and cloned PyWRKY71 from Populus yunnanensis and conducted a pot experiment to validate its enhanced functionality in conferring Cd tolerance to woody plants (poplar). During the experiment, the increase in plant height of the OE-87 line (overexpression poplar) was 1.46 times than that of the wild type (WT). Moreover, PyWRKY71 significantly promoted the accumulation of Cd in poplar, especially in the roots, where the Cd content in the OE-45 and OE-87 lines was 1.42 times than that in the WT. The chlorophyll content of transgenic poplar leaves was higher than that of the WT, reflecting a protective mechanism of PyWRKY71. Additionally, the activities of other antioxidants, including POD, SOD, CAT, and MDA, were elevated in transgenic poplars, bolstering their tolerance to Cd stress. In summary, PyWRKY71 exhibits substantial potential in regulating plant tolerance to Cd stress. This study not only provides a solid scientific foundation but also introduces a novel modified poplar variety for the remediation of Cd pollution.

Peculiarities of the formation of energy biomass by poplar plantations on the leached chernozems of the Central Forest Steppe of Ukraine

Purpose. To determine the energy biomass productivity of poplar variety 'Robusta' on leached chernozems of the Central Forest-Steppe of Ukraine during the first four years. Methods. Field, laboratory, and statistical. Results. The data of research on the growth of energy plantations of the 'Robusta' poplar variety during the first four years on leached chernozems of the Central Forest Steppe of Ukrainare presented. The plantation was established using one-year lignified 25 cm long cuttings that have a diameter in the upper section of 0.8–1.0 cm. The cuttings were planted according to two planting design: 2.0 × 0.8 m and 2.0 × 0.9 m. In both variants, at the end of the first vegetation season, the trees had an average height of 1.6 m. In the second vegetation season, the height increase in the first variant was 2 .0 ± 0.05 m, and on the second 2.1 ± 0.05 m. In the third year of cultivation, the growth of poplar trees reached the maximum height and amounted to 3.1 and 3.0 m, respectively, at the end of the year, with the average height of plants reaching 6.8 and 6.6 m, respectively. In the fourth year of vegetation, the increase in height slowed down significantly (to 1.2 and 1.1 m, respectively) and the average increase in plant height began to decrease significantly: their height was 8.0 ± 0.16 m in the first variant and 7.7 ± 0.22 m in the second. The average stem diameter of plants at a height of 1.3 m after the first year was higher in the first variant compared to the second (0.5 cm vs. 0.3 cm). However, already during the second year, the trees of the second (less dense) plantation increased their diameter by 2 cm. The same difference was preserved in the third year, when the average diameter of the trees of these variants was 5.8 and 6.2 cm, respectively. During the fourth growing season, the average increase in diameter in the studied plantations significantly decreased, and their average diameter indicators reached 7.2 ± 0.22 and 8.0 ± 0.31 cm, respectively. At the same time, there was a significant increase in the productivity indicators of such plantations at this time: from 25.78 to 29.94 t/ha, with energy yield ranging from 458.8 GJ/ha to 532.8 GJ/ha. This circumstance indicates the expediency of using a 5–7-year cycle of biomass harvesting on such plantations to obtain maximum productivity indicators. Conclusions. On the leached chernozems of the Central Forest Steppe of Ukraine, poplar energy plantations of 'Robusta' variety after three years of cultivation accumulate about 12–15 tons of dry biomass per 1 ha, and after four years from 26 to 30 tons of dry biomass per 1 ha. It is advisable to continue the study of the growth of such plantations in order to establish the optimal rotation of the coppice.

Assessment of the influence of the elements of cultivation technology and other factors on the growing of poplar seedlings

Purpose. To study the peculiarities of growing one-year seedlings obtained from cuttings of four black poplar cultivars in the Central Forest Steppe and the influence of agrotechnical measures and other factors on this process. Methods. For three years, the morphometric characteristics of the seedlings of poplar varieties 'Dorskamp', 'I‑45/51', 'Robusta', and Toropohrytskyi poplar, grown on chernozems of the Central Forest Steppe of Ukraine, were studied. One-year lignified 20, 25 and 30-cm long cuttings were used to obtain seedlings that were planted in two periods: autumn (late November) and spring (beginning of April) in the years 2019–2021. Results. For autumn planting, cuttings of Toropohrytskyi poplar had the highest height. It was, on average, over three years, 178.4 cm when using cuttings with a length of 20 cm, 188.7 cm with cuttings of 25 cm, and 197.0 cm with cuttings of 30 cm. The average height of seedlings of 'Dorskamp' variety ranged from 158.2 up to 170.3 cm, in 'Robusta' from 148.1 to 161.8 cm and in 'I–45/51' from 145.2 to 153.8 cm. Plants of 'Dorskamp' variety had the largest dimensions during spring planting, which ranged from 193.8 to 197.9 cm. The average height of Toropohrytskyi poplar plants was from 151.2 to 173.5 cm, of 'Robusta' variety from 131.9 to 149.1 cm, and of 'I–45/51' from 122.4 to 128.3 cm. At the same time, the plants from the shortest cuttings had the highest height in varieties 'Robusta' and 'I–45/51'. Conclusions. Of the studied cultivars cultivated on leached chernozems, it is primarily advisable to use Toropohrytsky poplar and 'Dorskamp' variety. The first one should be planted in autumn using 30-cm cuttings, and the second one should be planted in spring using 20-cm cuttings. Cuttings of the 'I-45/51' and 'Robusta' varieties should be planted in autumn. Their optimal length is 20 cm. The weight of one-year-old poplar cuttings and the proportion of their root system are most influenced by the time of planting, varietal characteristics and weather conditions of the growing season.

Genome-wide identification and expression analysis of PtJAZ gene family in poplar (Populus trichocarpa)

BackgroundThe jasmonate ZIM domain (JAZ) protein is a key repressor of the jasmonate signal transduction pathway, which plays an important role in plant growth and development and defense responses. In this study, based on the published whole-genome data, we identified members of the JAZ gene family in Populus trichocarpa. Through a series of bioinformatic approaches, their expression patterns under various stress conditions have been analyzed to explore and excavate the endogenous resistance genes of poplar and provide a theoretical basis for breeding new varieties of poplar resistance.ResultsA total of 13 PtJAZ genes have been identified in P. trichocarpa and designated as PtJAZ1–PtJAZ13. Those 13 PtJAZ genes were unevenly distributed on nine chromosomes, and they could be divided into four subfamilies. The gene structures and motif composition of the members derived from the same subfamily were similar. Collinearity analysis demonstrated that, compared with Arabidopsis thaliana and Oryza sativa, the most collinear pairs (13) were found in P. trichocarpa and Eucalyptus robusta. Cis-acting element analysis suggested that the promoter regions of PtJAZs contained a large number of hormones and stress response elements, of which abscisic acid (ABA) and methyl jasmonate (MeJA) hormone response elements were the most abundant. The PtJAZ genes not only had diverse expression patterns in different tissues, but they also responded to various abiotic and biotic stress conditions. The co-expression network and GO and KEGG analyses showed that JAZ genes were closely related to insect resistance.ConclusionsIn this study, applying bioinformatic methods, 13 PtJAZ gene family members from P. trichocarpa were identified and comprehensively analyzed. By further studying the function of the poplar JAZ gene family, the aim is to select genes with better insect resistance and stress resistance so as to lay a solid foundation for the subsequent breeding of new poplar varieties.

Prospects for the use of Walnut and Poplar in agroforestry of Polissya and Forest-Steppe of Ukraine

Climate changes actualise the need for the transition of Ukraine’s agricultural business to agroforestry systems not only in the steppe but also in the northern regions of the country. The purpose of the study is to examine the features of creating protective stands of Walnut (Juglans regia L.) and Poplars (Populus × euramericana) in Polissya and in the Forest-Steppe of Ukraine. Experimental plantings of Walnut were created by one-year-old seedlings on sod-podzolic sandy loam soils of Zhytomyr Polissya and on carbonate soils of the Western Forest-Steppe, and the analysis of the survival rate of Poplar plantings was conducted on chernozems of the Right-Bank Forest-Steppe. It was established that on sod-podzolic soils, five-year-old plants of Walnut had an average height of 91.8 cm. At the age of 4, some of them bore fruit. The fruit-bearing trees had higher indicators of average height of 13.4% and a diameter of 71.5% compared to the rest. On carbonate soils, the trees showed substantially better growth in height, which is explained by the calciphile nature of the nut. It is determined that an effective way to increase the survival rate of one-year-old seedlings of Poplar varieties Dorskamp, Robusta and I-45/51 is to plant them without trunks. In all the examined varieties, during the first two years, the highest survival rate of seedlings was in the variant without a trunk – from 57.0 to 68.9%, while in seedlings with a trunk – from 50.3% to 68.1%. In 2022, due to irrigation, the survival rate ranged from 74.4% to 88.9%. The average height was mostly also higher in plants that grew from seedlings without a trunk. It was the largest in plants of the Dorskamp clone – 188.6 to 209.3 cm. In uncut plants of this variety, it ranged from 174.0 to 197.2 cm. The practical importance of the study lies in the possibility of developing new forms of Walnut and Poplar and improving technologies for creating forest lands with their involvement, which can be used in Polissya and Forest-Steppe conditions

Heterologous expression of Zygophyllum xanthoxylon zinc finger protein gene (ZxZF) enhances the tolerance of poplar photosynthetic function to drought stress

The ZxZF transcription factor (TF) of Zygophyllum xanthoxylon (Bunge) Maxim, an extremely drought-resistant woody plant, is a C2H2 zinc finger protein. Studies have shown that C2H2 zinc finger proteins play important roles in activating stress-related genes and enhancing plant resistance. However, their function in regulating plant photosynthesis under drought stress is not well understood. Since poplar is an important greening and afforestation tree species, it is particularly important to cultivate excellent drought-tolerant varieties. The ZxZF transcription factor (TF) was heterogeneously expressed in Euroamerican poplar (Populus × euroameracana cl.'Bofengl’) by genetic transformation. Based on the mechanism and potential function of poplar photosynthesis regulated by ZxZF under drought stress, transcriptomic and physiological determinations were used to reveal the important role of this gene in improving the drought resistance of poplar. The results showed that the overexpression of ZxZF TF in transgenic poplars could improve the inhibition of Calvin cycle by regulating stomatal opening and increasing the concentration of intercellular CO2. The chlorophyll content, photosynthetic performance index, and photochemical efficiency of transgenic lines under drought stress were significantly higher than those of the wild type (WT). The overexpression of ZxZF TFs could alleviate the degree of photoinhibition of photosystems II and I under drought stress and maintain the efficiency of light energy capture and the photosynthetic electron transport chain. The transcriptomic data also showed that differentially expressed genes between the transgenic poplar and WT under drought stress were primarily enriched in metabolic pathways related to photosynthesis, such as photosynthesis, photosynthesis-antenna protein, porphyrin and chlorophyll metabolism, and photosynthetic carbon fixation, and the downregulation of genes related to chlorophyll synthesis, photosynthetic electron transport and Calvin cycle were alleviated. In addition, the overexpression of ZxZF TF can alleviate the inhibition of NADH dehydrogenase-like (NDH) cyclic electron flow of the poplar NDH pathway under drought stress, which plays an important role in reducing the excess pressure of electrons on the photosynthetic electron transport chain and maintaining the normal photosynthetic electron transport. In summary, the overexpression of ZxZF TFs can effectively alleviate the inhibition of drought on the assimilation of carbon in poplar and have a positive impact on light energy capture, the orderly transport of photosynthetic electron transport chain and the integrity of the photosystem, which is highly significant to acheivean in-depth understanding of the function of ZxZF TFs. This also provides an important basis for the breeding of new transgenic poplar varieties.

Growth and productivity of energy plantations of poplars in the Right-Bank Forest Steppe conditions

Purpose. To determine the features of the growth of an energy plantation of poplar variety ‘Robusta’ on leached chernozems in the conditions of the Central Forest Steppe of Ukraine. Methods. Field, laboratory, statistical. Results. One-year lignified cuttings 25 cm long and 0.8–1.0 cm in diameter were used as planting material. The designed layout of planting places: 2.0x0.8 m (more density version) and 2.0x0.9 m (more sparse version). After the first year of cultivation, the studied plots had the same height (1.6 m). During the second growing season, their growth in height was 2.0±0.05 m in the more sparse version, and 2.1±0.05 m in the thicker version. After the first year, the diameter at a height of 1.3 m was greater in the thicker version (0.5 cm versus 0.3 cm), but already in the next year, the trees of the more sparse stand became 2 mm thicker, and this difference persisted in the third year, when the average diameter of the trees of the denser version was 5.8 cm, and of the sparser — 6.2 cm. As a result of the higher diameter of trees of the more sparse version, they had a higher weight of the average tree, but due to the smaller number of trees, their productivity was lower. So, after three years of growing a poplar plantation created by cuttings, one hectare can yield 11.66–14.58 tons of dry biomass, or 207.5–259.5 GJ of energy. A sharp increase in morphometric indicators during the third year of cultivation indicates the feasibility of using a longer period of cultivation of such plantations to obtain the maximum amount of biomass. Conclusions. The study of a three-year energy plantation of the ‘Robusta’ variety, created by one-year lignified cuttings on the leached soils of the Right Bank Forest Steppe, with the placement of planting sites 2.0 x 0.8 m and 2.0 x 0.8 m, showed that after three years of growing a poplar plantation, one hectare can get 11.66–14.58 tons of dry biomass, or 207.5–259.5 GJ of energy. A significant increase in growth indicators and biomass productivity of poplar plantations during the third year of cultivation indicates the feasibility of using a 4–6-year period of cultivation of such plantations to obtain the maximum amount of biomass.

Integrated transcriptomic and metabolomic profiles reveal adaptive responses of three poplar varieties against the bacterial pathogen Lonsdalea populi.

Different poplar varieties vary in their tolerance to certain pathogens. However, knowledge about molecular regulation and critical responses of resistant poplars during pathogen infection remains scarce. To investigate adaptive responses to canker disease caused by the bacterium Lonsdalea populi, we screened three poplar varieties with contrasting tolerance, including Populus deltoides. 'Zhonglin 2025' (2025), Populus × Euramericana. '74/76' (107) and Populus tomentosa cv 'henan' (P. tomentosa). Transcriptomic analysis revealed significant changes in the expression levels of defence-related genes in different poplar varieties in response to infection, which reshaped the PTI and ETI processes. Intriguingly, photosynthesis-related genes were found to be highly expressed in the resistant variety, whereas the opposite was observed in the susceptible variety. Susceptible poplars maintained the activation of defence-related genes during early period of onset, which restricted the expression of photosynthesis-related and auxin signal-related genes. Furthermore, combined with metabolomic analysis, differences in the content of antibacterial substances and key differentially expressed genes in phenylpropane and flavonoid biosynthesis pathways were identified. Delayed induction of catechin in the susceptible variety and it's in vitro antibacterial activity were considered to be one of the important reasons for the differences in resistance to L. populi compared with the resistant variety, which is of practical interest for tree breeding. Moreover, the trade-off between growth and defence observed among the three poplar varieties during infection provides new insights into the multilevel regulatory circuits in tree-pathogen interactions.

Differences in detoxification mechanism and gene expression changes of sulfur metabolism in coping with the air pollutant SO2 between the resistant and ordinary poplar variety

In this study, two poplar varieties with different resistance to sulfur dioxide were selected for a comparative experiment. SO2 fumigation to the poplars was carried out under controlled conditions to determine the variation in the activity of enzymes, the content of metabolites and the expression of enzymes genes in pathways of sulfur metabolism in plants. The results showed that the activity of enzymes and the content of sulfur metabolites were closely related to the response of the poplars to SO2 stress. Populus × euramericana cv. 'Purui' had two ways of detoxification: oxidation detoxification, oxidizing sulfite (SO32−) to sulfate SO42− by sulfite oxidase; reductive detoxification, SO32− being reduced to S2− by sulfite reductase (SiR). Moreover, OASTL and SAT activity, and levels of cysteine (CYS) and glutathione (GSH) also increased in P. × euramericana cv. 'Purui' in response to SO2 fumigation, and the gene expression encoding Glutathione S-transferases (GST), and some enzymes in cysteine and methionine metabolism was up-regulated. For Populus × euramericana cv. '74/76' with weaker resistance to sulfur dioxide, it only detoxified by increasing the activity of SiR, and but down-regulated the expression of gene encoding 3'-phosphoadenosine 5'-phosphosulfate synthase (PAPSS), which could affect the consumption of sulfite in the exposure to SO2. Thus, the SO2-resistant difference of the two poplar varieties is mainly attributed to variation in activity of the enzymes and content of their metabolites in pathways of sulfur metabolism, and gene expression of some enzymes in cysteine and methionine metabolism also plays a role in the resistant difference.

Application of polygene polymerization for insect-resistant poplar breeding

A major goal of poplar breeding is to obtain new insect-resistant poplar varieties through genetic engineering. However, engineering poplars with only a single insect-resistant gene has limitations, such as narrow insecticidal bands and the rapid development of insect tolerance to the gene. To expand insecticidal bands, delay the development of insect tolerance, and improve the insect resistance of transgenic poplars, polygene polymerization is increasingly being applied to cultivate insect-resistant poplars. In the present study, we discuss polygene polymerization, applications of the polygene combination strategy, the current state of research on transgenic poplar with multiple insect-resistant genes, including existing problems, and future research directions. We provide reference data to aid the cultivation and utilization of new polygenic insect-resistant poplar varieties.

Growth and productivity of poplar nursery plantations under different heights of cutting shoots

Purpose. To develop major agrotechnical measures for growing the maximum number of one-year lignified poplar cuttings for the establishment of energy plantations in the conditions of the Right Bank Forest Steppe of Ukraine. Methods. Field, laboratory, statistical. Results. Nursery plantings of three poplar varieties were studied: one-year plantation of variety 'Dorskamp' and three-year plantations of varieties 'Robusta' and 'I-45/51'. At this age in the spring of 2019, the plants were cut at a height of 0.00, 0.25, 0.50 and 1.00 m from the ground surface. Plants of 'Dorskamp' variety that were cut at 0.00 m grew to a height of 2.27±0.124 m for 1 year, at 0.25 m to 2.85±0.135 m and at 0.50 m to 2.81±0.143 m. In the subsequent years, after cutting, the height of plants of 'Dorskamp' variety increased as follows: in 2020 to 3.01±0.231 m, 3.22±0.170 m and 3.30±0.170 m; in 2021, to 3.53±0.230 m, 4.11±0.129 m and 3.85±0.188 m, respectively. 'Robusta' variety in the first year after cutting had the highest average height indicators that decreased with each subsequent year (except for the height of 100 cm). One-year shoots of 'I-45/51' variety were the highest in 2020. In 2021, they had the maximum height indicators of the three varieties, 4.50±0.165 m. The yield of cuttings from 1 ha of the nursery plantation of 'Dorskamp' variety in 2019 varied from 166.6 thousand shoots/ha for cutting at a height of 0.25 m to 184.9 thousand shoots/ha at a height of 0.00 m. In the following 2 years, the yield of cuttings increased both with the increase in the age of the plantation and the cutting height. In the third year (2021), 'Dorskamp' had the maximum indicators, 397.2 thousand shoots/ha at a cutting height of 0.25 m. In 'Robusta' variety, already in the next year after the first cutting, the yield of cuttings ranged from 942.5 to 2621.3 thousand shoots/ha. At the same time, the yield increased significantly with an increase in cutting height and in most cases decreased in subsequent years. In 'I-45/51' variety, the yield of standard shoots in the first year after cutting increased with an increase in cutting height from 105.8−101.3 thousand shoots/ha to 200.6 thousand shoots/ha (at a height of 1.0 m). In 2020, it was from 128.2 thousand shoots/ha to 226.0 thousand shoots/ha, respectively, for cutting at 0.00 m and 1.00 m. In 2021, the yield of shoots in the variants 0.00 m and 0.50 m slightly decreased, and for cutting at heights of 0.25 and 1.00 m increased to 134.3 and 265.5 thousand shoots/ha, respectively. Conclusions. The productivity of poplar nursery plantations in the conditions of the research region is largely affected by the varietal characteristics, the age of the plants, and the weather conditions of a certain year. Among the varieties used in the study, the maximum yield of standard planting material (shoots) is noted in nursery plantations of 'Robusta', amounting to 2.6 million shoots/ha. 'I-45/51' variety had much lower productivity, up to 0.26 million shoots/ha. The plantation of 'Dorskamp' variety, 2 years younger than 'Robusta' and 'I‑45/51', had a yield of shoots per hectare up to 0.40 million. The highest yield of planting material in most cases was ensured by the cutting at 0.50–1.00 m.