Juglans Mandshurica Research Articles

A novel LC-MS/MS method for complete composition analysis of polysaccharides by aldononitrile acetate and multiple reaction monitoring

Carbohydrate analysis has always been a challenging task due to the occurrence of high polarity and multiple isomers. Aldoses are commonly analyzed by gas liquid chromatography (GLC) following aldononitrile acetate derivatization (AND). However, the GLC technique cannot be applied for the simultaneous determination of aldoses, ketoses, and uronic acids. In this study, a new method based on the combination of liquid chromatography-tandem mass spectrometry (LC-MS/MS) and AND is developed for the complete characterization of monosaccharide composition (i.e., aldoses, ketoses, alditols, amino sugars, and uronic acids) in plant-derived polysaccharides. In addition to discussing the possible byproducts, the study optimizes the multiple reaction monitoring (MRM) parameters and LC conditions. The final separation of 17 carbohydrates is performed on a BEH Shield RP18 column (150 mm × 2.1 mm, 1.7 μm) within 25 min, without using any buffer salt. Notably, the complex polysaccharides extracted from Ligusticum chuanxiong, Platycodon grandiflorum, Cyathula officinalis Kuan, Juglans mandshurica Maxim, and Aralia elata (Miq.). Seem bud can be successfully characterized using the developed method. Overall, the results demonstrated that the newly established LC-MS/MS MRM method is more effective and powerful than the GLC-based methods reported previously, and it is more suitable for the analysis of highly complex natural polysaccharides, including complex pectins, fructosans, and glycoproteins.

Recent demographic histories of temperate deciduous trees inferred from microsatellite markers

BackgroundAccurate inference of demographic histories for temperate tree species can aid our understanding of current climate change as a driver of evolution. Microsatellites are more suitable for inferring recent historical events due to their high mutation rates. However, most programs analyzing microsatellite data assume a strict stepwise mutation model (SMM), which could cause false detection of population shrinkage when microsatellite mutation does not follow SMM.ResultsThis study aims to reconstruct the recent demographic histories of five cool-temperate tree species in Eastern Asia, Quercus mongolica, Q. liaotungensis, Juglans cathayensis, J. mandshurica and J. ailantifolia, by using 19 microsatellite markers with two methods considering generalized stepwise mutation model (GSM) (MIGRAINE and VarEff). Both programs revealed that all the five species experienced expansions after the Last Glacial Maximum (LGM). Within butternuts, J. cathayensis experienced a more serious bottleneck than the other species, and within oaks, Q. mongolica showed a moderate increase in population size and remained stable after the expansion. In addition, the point estimates of the multistep mutation proportion in the GSM model (pGSM) for all five species were between 0.50 and 0.65, indicating that when inferring population demographic history of the cool-temperate forest species using microsatellite markers, it is better to assume a GSM rather than a SMM.ConclusionsThis study provides the first direct evidence that five cool-temperate tree species in East Asia have experienced expansions after the LGM with microsatellite data. Considering the mutation model of microsatellite has a vital influence on demographic inference, combining multiple programs such as MIGRAINE and VarEff can effectively reduce errors caused by inappropriate model selection and prior setting.

Juglone regulates gut microbiota and Th17/Treg balance in DSS-induced ulcerative colitis

Juglone, mainly isolates from the green walnut husks of Juglans mandshurica, exhibits anti-cancer and anti-inflammaroty activities. But its protection on ulcerative colitis (UC) has never been explored. In this study, we first evaluated whether juglone ameliorated UC, and investigated its effects on gut microbiota and Th17/Treg balance in DSS-induced UC mice model. The model was established by administrating 2.7% DSS for seven days. Juglone was given daily by gavage for ten days, once a day. The disease activity index (DAI) decrease and pathological characteristics improvement demonstrated that the UC in mice was alleviated by juglone. Juglone treatment significantly inhibited the protein levels of IL-6, TNF-α and IL-1β, improved the protein expression of IL-10. In addition, juglone altered microbial diversity and gut microbiota composition, including the enhancement of the ratio of Firmicutes to Bacteroidota and the abundance of Actinobacteriota, and decrease of the abundance of Verrucomicrobiota. Juglone treatment also inhibited the protein expressions of IL-6, STAT3 and RORγt, meanwhile improved the protein level of FOXP3. Furthermore, juglone inhibited Th17 development and increased Treg generation, beneficial to Th17/Treg balance. Together, we herein provided the first evidence to support that juglone, especially the high dose, possibly protected mice against UC by modulating gut microbiota and restoring Th17/Treg homeostasis.

Improved de novo chromosome-level genome assembly of the vulnerable walnut tree Juglans mandshurica reveals gene family evolution and possible genome basis of resistance to lesion nematode.

Manchurian walnut (Juglans mandshurica Maxim.) is a synonym of J.cathayensis, a diploid, vulnerable, temperate deciduous tree valued for its wood and nut. It is also valued as a rootstock for Juglans regia because of its reported tolerance of lesion nematode. Reference genomes are available for several Juglans species, our goal was to produce a de novo, chromosome-level assembly of the J.mandshurica genome. Here, we reported an improved assembly of J.mandshurica with a contig N50 size of 6.49Mb and a scaffold N50 size of 36.1Mb. The total genome size was 548Mb encoding 29,032 protein coding genes which were annotated. The collinearity analysis showed that J.mandshurica and J.regia originated from a common ancestor, with both species undergoing two WGD events. A genomic comparison showed that J.mandshurica was missing 1657 genes found in J.regia, and J.mandshurica includes 2827 genes not found in of the J.regia genome. The J.mandshurica contained 1440 unique paralogues that were highly enriched for flavonoid biosynthesis, phenylpropanoid biosynthesis, and plant-pathogen interaction. Four gene families related to disease resistance notable contraction (rapidly evolving; LEA, WAK, PPR, and PR) in J.mandshurica compared to eight species. JmaPR10 and JmaPR8 contained three orthologous gene pairs with J.regia that were highly expressed in root bark. JmaPR10 is a strong candidate gene for lesion nematodes resistance in J.mandshurica. The J.mandshurica genome should be a useful resource for study of the evolution, breeding, and genetic variation in walnuts (Juglans).

Arbuscular mycorrhizal trees cause a higher carbon to nitrogen ratio of soil organic matter decomposition via rhizosphere priming than ectomycorrhizal trees

Tree roots and their associated microbes can significantly influence soil organic matter (SOM) decomposition, i.e., the rhizosphere priming effect. This effect is expected to be greater in trees associated with arbuscular mycorrhizal (AM) fungi, which produce higher extracellular enzymes especially surrounding hyphae, than in trees associated with ectomycorrhizal (ECM) fungi. Here, we selected five tree species associated with AM (Juglans mandshurica Maxim. and Cunninghamia lanceolata (Lamb.) Hook.) or ECM (Picea koraiensis Nakai, Quercus mongolica Fischer ex Turcz. and Larix kaempferi (Lamb.) Carriere). We grew tree seedlings inside of cores lined with different mesh sizes to investigate how roots, hyphae and exudates influence soil carbon (C) and nitrogen (N) mineralization via the rhizosphere priming effect, using a13C natural abundance approach and a15N pool dilution method, concurrently. We found that tree seedlings significantly accelerated soil C decomposition by on average 78%, i.e., positive priming, compared to unplanted control pots. AM-associated trees induced 2.1 times greater soil C decomposition than ECM-associated trees across all mesh sizes. In contrast, gross N mineralization did not differ between tree-mycorrhizal associations. Compared to ECM counterparts, AM-associated trees had higher C- and lower N-degrading enzyme activities. Consequently, AM-associated trees induced a significantly higher C:N ratio of SOM decomposition than their ECM counterparts, which could be associated with the differences in soil enzyme activities for C and N degradation. Further, for both AM- and ECM-associated trees, we found no significant influences of mesh size on soil C decomposition, suggesting that the rhizosphere priming effect of mycorrhizal symbiosis was predominantly driven by root exudates. We conclude that SOM decomposition caused by AM-associated trees may have a higher C:N ratio than that by ECM-associated trees mainly due to differences in microbial enzyme investment. Our findings imply that tree-mycorrhizal associations are capable of modulating soil biogeochemical cycling via the rhizosphere priming effect.

Flower Development of Heterodichogamous Juglans mandshurica (Juglandaceae).

Juglans mandshurica is a monoecious heterodichogamous species with protogynous and protandrous mating strategies that occur at a 1:1 ratio and are randomly distributed in the population. The inconsistent male and female flowering periods of the same mating type result in an imbalance of the ratio of male and female flowers, contributing to the low yield of this species. However, little more is known about its floral development. Following three consecutive years of observations, histological analysis, and scanning electron microscopy, we found that the morphological and anatomical development of the male and female flowers were synchronous. The male floral morphological development of J. mandshurica was divided into seven phases, while that of the female flower was nine. Four stages were shared between the male and female flower’s anatomical development. Our findings indicate that there was minimal overlap between sexual functions within the same mating type, guaranteeing synchronization, mutual non-interference, outcrossing, and avoidance of self-fertilization. These results provide a theoretical basis for the improvement of fruit yield and quality through the reasonable allocation of protogynous and protandrous individuals in a population, and for artificial pollination control. Further, these findings lay a foundation for further research on the genetic mechanisms and environmental effects on flower development of heterodichogamous J. mandshurica.

A systematic evaluation of gap size and within-gap position effects on seedling regeneration in a temperate secondary forest, Northeast China

Forest gaps play an important role in tree regeneration and forest restoration in modern silviculture. Many previous studies examined gap effects on seedling survival, growth, or both but lacked a systemic assessment incorporating morphological and physiological responses to varying environmental gradients along gap size and within-gap position, which limits foresters to understand the general gap impacts on the early stage of regeneration. Here, we systemically evaluated gap impacts on over 20 regeneration-related variables from two dominant tree species (Manchurian walnut [Juglans mandshurica Maxim.] and Korean spruce [Picea koraiensis Nakai]) planted along the gap-understory gradients based on our previous studies of survival and growth of these two species. The factor analysis of mixed data indicated that seedling specific leaf area, biomass allocation, chlorophyll content, and NSC content in gaps were largely determined by interspecific differences, but seedling survival, growth, and biomass accumulation were mainly related to gap size and within-gap position. Specifically, the net photosynthetic rates of Manchurian walnut were higher in large and medium gaps (or gap centers and transitions) than those in small gaps and forest understory (or gap edges). The root starch content of seedlings in gaps was almost twice as much as that in the forest understory, which also reflected species divergence in gaps. By contrast, Korean spruce exhibited less variation in net photosynthesis and root starch content and fewer differences for most other examined variables, which indicated that it had broad ecological niches and a relatively small gap would promote its regeneration during the seedling stage. Our findings provide evidence of gap partitioning on explaining regeneration patterns of light-demanding species. Therefore, gap size and within-gap position can compensate for each other during gap-based silviculture practices. Timely selective logging can extend an existing gap in a specific direction to change the relative position of target tree species for better light conditions. Appropriate selection and match of tree species to gap size and within-gap position during enrichment planting can improve gap space utilization.

Juglans mandshurica Maxim.: A Review of Its Traditional Usages, Phytochemical Constituents, and Pharmacological Properties.

Juglans mandshurica Maxim., also known as “Manchurian walnut” (Chinese) and “Onigurumi” (Japanese), is a medicinal plant widely distributed in Western and Central Asia, especially in China. It has been traditionally used to treat cancer, gastric ulcers, diarrhea, dysentery, dermatosis, uterine prolapse, and leukopenia. To date, more than 400 constituents including quinones (e.g. naphthoquinones, anthraquinones, naphthalenones, tetralones), phenolics, flavonoids, triterpenoids, coumarins, lignans, phenylpropanoids, diarylheptanoids, and steroids, were isolated and structurally identified from different plant parts of J. mandshurica. Among them, quinones, phenolics, triterpenoids, and diarylheptanoids, as the major bioactive substances, have been extensively studied and displayed significant bioactivity. Previous studies have demonstrated that J. mandshurica and a few of its active components exhibit a wide range of pharmacologically important properties, such as antitumor, immunomodulatory, anti-inflammatory, neuroprotective, anti-diabetic, antiviral, antimicrobial, and anti-melanogenesis activities. However, many investigations on biological activities were mainly based on crude extracts of this plant, and the major bioactive ingredients responsible for these bioactivities have not been well identified. Further in vitro and in vivo studies on the mechanisms of action of the pure bioactive compounds, and more elaborate toxicity studies as well as clinical studies are needed to ensure safety and effectiveness of the plant for human use. Taken together, the present review will provide some specific useful suggestions guide to further investigations and applications of this plant in the preparation of medicines and functional foods.

Intra- and inter-species variations in carbon content of 14 major tree species in Northeast China

Reducing greenhouse gas emissions is one of the major challenges in combating global warming. Carbon, including in the form of carbon dioxide (CO2), is considered an essential greenhouse gas under human control to demonstrate success in emission reductions. However, many carbon stock quantifications in forest ecosystems still rely on the estimated 50% carbon content instead of more precise species-, tissue- and site-specific values. Thus, this study aimed to thoroughly measure and analyze the carbon content and variability using the 14 major tree species in Northeast China. Over 600 trees were destructively sampled from three different major mountainous regions (i.e., the Changbai, Daxing’an, and Xiaoxing’an mountains), and the carbon contents of each species were precisely measured to the sub-tissue level. Carbon contents varied significantly between species, with foliage carbon mostly found to be the highest, while root carbon contents were the lowest. Average carbon contents can be ranked as: Ulmus laciniata (43.4%) < Phellodendron amurense (43.5%) < Acer mono (43.8%) < Tilia amurensis (44.2%) < Populus davidiana (44.5%) < Fraxinus mandshurica (44.7%) < Juglans mandshurica (44.9%) < Quercus mongolica (45.3%) < Betulla davurica (45.8%) < Betulla platyphylla (46.7%) < Picea koreansis (46.9%) < Larix gmelinii (47.4%) < Pinus koreansis (48.3%) < Abies nephrolepis (48.3%). Carbon contents were higher in conifers (47.7%) compared to broadleaf species (44.9%). In addition, both tree tissues and growing sites also had a significant effect on carbon content. At the sub-tissue level, only stem’s sub-tissues (i.e., bark, heartwood, and sapwood) carbon contents showed significant variations. The results suggest that bark should be separated from other stem sub-tissues and considered separately when determining carbon stocks. This research contributes to improving estimates of terrestrial carbon quantifications, and in particular, the values obtained can be used in China’s National Forest Inventory.

Breeding research of genus Juglans representatives on the territory of EBDFC "Veseli Bokovenki"

Aim. To summarize the results on the breeding of the genus Juglans representatives within the territory of the Experimental and Breeding Dendrological Forest Center "Veseli Bokovenki" and to outline the prospects for future research. Results and Discussion. The current state, research results and prospects of using collections of breeding forms of the genus Juglans representatives at the Experimental Breeding Dendrological Forest Center (EBDFC) "Veseli Bokovenki" are analyzed. The 2016 survey showed that 7 out of 10 experimental objects derived from the genus Juglans representatives over a 120-year period have been preserved and are in a satisfactory condition within the territory of the Center. They are all in the context of the gene pool value. The Persian walnut (Juglans regia L.) breeding history within the territory of EBDFC "Veseli Bokovenki" started with the creation of the Big and Small Kutsivsky gardens by M.L.Davydov in 1900. Planned scientific research into the Persian walnut breeding started here in the 1930s. In different periods of time, under the guidance of A.P.Yermolenko, F.L.Shchepotiev and P.P.Badalov, selection of drought-resistant and winter-hardy forms, interspecies hybridization and studies of reproduction and physiology of the genus Juglans representatives were carried out. Apomictic fruits of the Japanese walnut (Juglans ailantifolia Carriere), heartnut (J. ailantifolia Carr. ssp. cordiformis Rehd), Manchurian walnut (Juglans mandshurica Maxim) and white walnut (Juglans cinerea L.) were obtained. The breeding results were summarized in chapters of the books "Nut Cultivation" and "Nuts". Recently, studies have focused on reproductive biology of breeding forms. The dichogamy type and laterality degree of the 80 best forms presented on the mother-graft plantation have been determined. The vast majority of the studied Persian walnut breeding forms are protandrous. Forms giving good yields in the harsh steppe conditions have been identified. Conclusions. All objects need preserving and wider using as a basis for breeding research. The priority objectives of further studies are phenotypic and genotypic diversity, reproductive biology and adaptability of the best forms of the Persian walnut and interspecies hybrids of the genus Juglans, inheritance of economically valuable traits, identification of more valuable forms and their involvement in subsequent breeding. The best cultivars need to be popularized, propagated vegetatively and introduced into nut industry, forestry, forest melioration and gardening.

Two new quinones and six additional metabolites with potential anti-inflammatory activities from the roots of Juglans mandshurica

Two new quinones, 4-(5-hydroxy-1,4-dioxo-1,4-dihydronaphtha-len-3-ylamino)-butyric acid methyl ester (compound 1) and 1,3-dimethoxycarbonyl-8-hydroxy-9,10-anthraquinone (2), and six known compounds (3–8) were isolated from the roots of Juglans mandshurica Maxim., a member of the Juglandaceae family. The chemical structures of the compounds were elucidated by nuclear magnetic resonance spectroscopy and compared with data from the literature. The isolated compounds were evaluated for their ability to inhibit the production of nitric oxide, tumour necrosis factor-α, and interleukin-6 by the mouse macrophage RAW 264.7 cell line after lipopolysaccharide stimulation in vitro. We found that compounds 1–4 exhibited potent anti-inflammatory effects, as indicated by suppression of lipopolysaccharide-stimulated nitric oxide and cytokine production with 50% inhibitory concentrations between 20.09 μM and 27.63 μM. These results identify two novel quinones from J. mandshurica with potential utility as anti-inflammatory compounds.

Two novel compounds from green walnut husks (Juglans mandshurica Maxim.)

Phytochemical investigation on the ethanol extract of green walnut husks (Juglans mandshurica Maxim.) led to the isolation of two previously unknown compounds, including a macrolide compound (13S)-8-oxo-(9E, 11E)-8-oxo-octadeca-9,11-dien-13-olide (1) and a diarylheptanoid compound 1-(3′-methoxy-4′-hydroxyphenyl)-7-(3″,4″-dimethoxyphenyl)heptan-3-one (2), together with 19 known compounds. The structures of these 21 compounds were elucidated by extensive analyses of NMR and HR-MS data, and the basis of spectroscopic analysis.

Substrate specialization and distribution of fungi of the genus &lt;i&gt;Trametes&lt;/i&gt; in the southeast of Western Siberia

The authors have studied the features of the substrate specificity of fungi of the genus Trametes s.l. in the southeast of Western Siberia, where this taxon has 10 species. Most species of fungi have a wide substrate spectrum, represented by the wood of various types of woody plants. Fungal species with a wide distribution and a high frequency of occurrence develop a wide range of substrates. Fungal species that are rare and common only in some localities are not numerous; they are characterized by a narrow substrate spectrum. Most species of fungi develop on hardwood, but only a few species can grow on coniferous wood in mountainous areas. Fungal substrates are represented by wood of sixteen species of angiosperms and one species of gymnosperms of woody plants. These ten species of fungi of the Trametes genus have been identified in natural plant communities in the southeast of Western Siberia, while only eight species have been found in anthropogenic habitats. The largest number of fungal species develops on large-sized tree species found in plant communities that are common in the studied region. The number of species of wood-decay fungi on shrubs is insignificant. A small range of species of wood-decay fungi is typical of introduced species (Linden, Oak, Manchurian Walnut, Apple, Ash, Mulberry) growing in urban plantings and in Botanical gardens. Species of fungi with a wide ecological amplitude can develop on the wood of introduced plants.

Modified photochemical reflectance index to estimate leaf maximum rate of carboxylation based on spectral analysis.

The maximum rate of carboxylation in leaves (Vcmax) is an important parameter used to determine the photosynthetic rate. An accurate estimation of Vcmax is important for evaluating the photosynthetic capacity of vegetation productivity and the carbon budget of forest ecosystems. In this study, we measured the light use efficiency (LUE) and Vcmax of leaves and their corresponding spectral characteristics. Spectral analysis was used to find a modified photochemical reflectance index (PRI) of leaves to estimate LUE and thereby estimate leaf Vcmax. The results showed that the precision with which the modified ratio PRI index estimated LUE was significantly increased. The R2 of the estimation model was 0.69, and the root mean square error (RMSE) was 0.0024. The R2 of the model for estimating leaf Vcmax based on the LUE was 0.72, and the RMSE was 8.439 μmol/m2/s. The Vcmax values of conifer trees (Scots pine, Korean pine, and larch) were higher than those of broadleaf trees (white birch, Manchurian walnut, Siberian elm, Manchurian ash, Mongolian oak, Korean aspen, and Amur linden). This method avoids problem that conventional PRI is not sensitive to high leaf LUE values and provides important parameter data for the quantitative estimation of the gross primary productivity of forest ecosystems.

Laboratory germination and storage of seeds of tree and shrub introduced species

The article presents the results of research on laboratory germination of seeds of tree and shrub introduced species. Introduced seeds were collected from existing plantings in Irkutsk and the Irkutsk region. To speed up germination and increase the percentage of germination, seed stratification was performed. Seeds of Spiraea media, Betula pendula, Picea obovata, Picea pungens, Pinus sylvestris, as a rule, do not require stratification, or for violation of shallow rest, the seeds need short-term cooling (for several hours, days or weeks). Cold stratification is required for seed germination of Betula ermanii, Clematis fusca, Corylus avellana, Juglans mandshurica, Phellodendron amurense, Syringa vulgaris . Multistage stratification is recommended for Schisandra chinensis seeds. Within a few days, the seeds of Populus alba and Scopulus balsamifera lose their ability to germinate. Quercus mongolica seeds completely lose their germination by spring sowing when stored dry. Seeds of Corylus avellana, Juglans mandshurica, Phellodendron amurense, Schisandra chinensis can be stored for only one year. The shelf life of Betula ermanii and Betula pendula seeds is 3-4 years. Picea obovata, Picea pungens, Pinus sylvestris retain germination for 4-5 years. Studies have shown that the shelf life of Spiraea media, Syringa vulgaris, Clematis fusca seeds for 4-5 years did not affect the percentage of their germination.

Assessment of the Phytin Content in the Fruit of Five Species of Juglans when Introduced in Central Russian Upland

The phytin (myo-inositol-1,2,3,4,5,6-hexacystichydrophosphoric acid) content was studied in the endosperm of five species of Juglans grown in the Central Russian Upland conditions: 1) Persian walnut (Juglans regia L.); 2) Manchurian walnut (Juglans mandshurica Maxim); 3) heartnut (Juglans cordiformis Maxim); 4) grey walnut (Juglans cinerea L.); 5) black walnut (Juglans nigra L). The walnut is shown to have the highest phytin content (31.90±0.67 mg/g wet weight) and a low coefficient of variation (Cv=4.23%). Based on the research, we can conclude that walnut is well adapted to the conditions of the Central Russian Upland and is recommended for the creation of fruit plantations by seed.

Long-term effects of mixed planting on arbuscular mycorrhizal fungal communities in the roots and soils of Juglans mandshurica plantations

BackgroundEstablishing mixed plantations is an effective way to improve soil fertility and increase forest productivity. Arbuscular mycorrhizal (AM) fungi are obligate symbiotic fungi that can promote mineral nutrient absorption and regulate intraspecific and interspecific competition in plants. However, the effects of mixed plantations on the community structure and abundance of AM fungi are still unclear. Illumina MiSeq sequencing was used to investigate the AM fungal community in the roots and soils of pure and mixed plantations (Juglans mandshurica × Larix gmelinii). The objective of this study is to compare the differential responses of the root and rhizosphere soil AM fungal communities of Juglans mandshurica to long-term mixed plantation management.ResultsGlomus and Paraglomus were the dominant genera in the root samples, accounting for more than 80% of the sequences. Compared with that in the pure plantation, the relative abundance of Glomus was higher in the mixed plantation. Glomus, Diversispora and Paraglomus accounted for more than 85% of the sequences in the soil samples. The relative abundances of Diversispora and an unidentified genus of Glomeromycetes were higher and lower in the pure plantation, respectively. The Root_P samples (the roots in the pure plantation) had the highest number of unique OTUs (operational taxonomic units), which belonged mainly to an unidentified genus of Glomeromycetes, Paraglomus, Glomus and Acaulospora. The number of unique OTUs detected in the soil was lower than that in the roots. In both the root and soil samples, the forest type did not have a significant effect on AM fungal diversity, but the Sobs value and the Shannon, Chao1 and Ace indices of AM fungi in the roots were significantly higher than those in the soil.ConclusionsMixed forest management had little effect on the AM fungal community of Juglans mandshurica roots and significantly changed the community composition of the soil AM fungi, but not the diversity.

Seasonal variation of diversity and co-occurrence patterns of arbuscular mycorrhizal fungal communities in mixed broadleaf-conifer forests

Arbuscular mycorrhizal (AM) fungi are an important determinant of plant performance. The temporal distribution patterns of AM fungal communities, important groups in forest soil, are affected by various environmental factors. However, the effect of seasonal variation on AM fungal communities in forest soil is still not fully understood. To improve knowledge regarding the seasonal dynamics of AM fungal communities in forest soil, the Juglans mandshurica rhizosphere soil in a 30-year-old natural J. mandshurica and Larix gmelinii mixed forest in northeastern China was sampled and studied during different seasons. AM fungal community composition and structure in the rhizosphere soil were determined by using the Illumina MiSeq sequencing platform. The results showed that forest type significantly affected soil pH and the microbial biomass carbon (Cmic), microbial biomass nitrogen (Nmic), C, N, P, NH4+-N and NO3−-N contents. Similarly, soil moisture significantly decreased with seasonal progression in all forest types. Glomus and Diversispora were the dominant genera. The Shannon, Sobs and Chao1 indices of the mixed forest were higher in July than in May and September. The NO3−-N and water-soluble phenol (WSPh) contents were the most important factors driving the shift in the soil AM fungal community across the seasonal gradient. Network analysis revealed that AM fungal network structure was significantly different between seasons, and the number of links between species significantly increased with time. We observed a clear tendency for mixed forest management to significantly affect AM fungal community structure and composition but not diversity. Furthermore, the co-occurrence network and keystone taxa among AM fungi can change in response to environmental filtering due to mixed management in different seasons.

Biocontrol and growth-promoting effect of Trichoderma asperellum TaspHu1 isolate from Juglans mandshurica rhizosphere soil

To better apply the biocontrol agent Trichoderma spp. in Northeast China, collecting and screening more suitable native Trichoderma strains is necessary. In the present study, 10 isolates were obtained from Juglans mandshurica rhizosphere soils in Heilongjiang Province, and were identified as T. asperellum (four isolates), T. harzianum (four), T. hamatum (one), T. atroviride (one). The fastest-growing isolate per species on potato dextrose agar medium were further evaluated in stress tolerance tests (salt, alkali, nutritional stress, and low temperature) and confrontation assays (eight pathogens), which showed that T. asperellum TaspHu1 possessed the best adaptation and biological control ability. Then, Solanum lycopersicum (tomato) seeds were sown and treated with a series of concentrations of TaspHu1 spore suspension, as was unsown soil. Tomato seedlings treated by TaspHu1 had a significantly greater height, stem diameter, soluble protein content and soluble sugar content. Furthermore, their nitrate reductase activity and catalase activity were significantly increased, and these promoting effects depended on the concentration of the spore suspension. Meanwhile, a decrease in chlorophyll content was observed in the tomato seedlings treated with TaspHu1. In addition, strain TaspHu1 enhanced the tomato seedlings’ absorption of available nitrogen, but did not influence the soil available nitrogen content. Furthermore, the resistance of tomato seedlings against Alternaria alternata was enhanced by TaspHu1 (smaller, fewer leaf spots), the seedlings’ hormone signal transduction genes JAR1, MYC2, NPR1, PR1, and GH3.2 were highly expressed. Thus, TaspHu1 is a promising biocontrol candidate for use in agriculture and forestry.

Two new dammarane-type triterpenoids from the green walnut husks of Juglans mandshurica Maxim

Two new dammarane-type triterpenoids, dammar-3α,12(R),20(S)-triol-12,32(R);20,32-diepoxy-25-methy-25-en-tridecacyclic ether (1) and (23E)-12β,20(R),25(S),26-tetrahydroxydammar-23-en-3-one (2) were isolated from the green walnut husks of Juglans mandshurica Maxim together with six known compounds. Their structures were elucidated through extensive spectroscopic analyses and by comparison with the literature, and the cytotoxic activities of these compounds were evaluated.