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Acacia melanoxylon (blackwood) is a valuable wood with excellent-quality heartwood extensively utilized worldwide. The main aim of this study was to confirm the horizontal and vertical variation and provide estimated values of genetic gains and clonal repeatabilities for improving breeding program of A. melanoxylon. Six blackwood clones at 10 years old were analyzed in Heyuan and Baise cities in China. Stem trunk analysis was conducted for sample trees to explore the differences between heartwood and sapwood. The heartwood radius (HR), heartwood area (HA), and heartwood volume (HV) in heartwood properties decreased as tree height (H) in growth traits increased, and the HV = 1.2502 DBH (diameter at breast height)1.7009 model can accurately estimate the heartwood volume. Furthermore, G × E analysis showed that the heritabilities of the eleven indices, including DBH, DGH (diameter at ground height), H, HR, SW (sapwood width), BT (bark thickness), HA, SA (sapwood area), HV, HRP (heartwood radius percentage), HAP (heartwood area percentage), and HVP (heartwood volume percentage) were between 0.94 and 0.99, and repeatabilities of the eleven indices were between 0.74 and 0.91. Clonal repeatability of DBH (0.91), DGH (0.88), and H (0.90) in growth traits, HR (0.90), HVP (0.90), and HV (0.88) in heartwood properties were slightly higher than for SA (0.74), SW (0.75), HAP (0.75), HRP (0.75), and HVP (0.75). These data also implied that the growth characteristics of heartwood and sapwood of blackwood clones were less affected by the environment and had substantial heritability.

A high-efficiency regeneration and genetic transformation system is indispensable for generating desirable traits in important trees such as Eucalyptus. However, lower regeneration efficiency is common for most varieties because of the recalcitrance of this genus. Here, a stable and highly efficient in vitro organogenesis protocol and Agrobacterium-mediated genetic transformation system of Eucalyptus were developed, and transgenic plants were obtained. In this protocol, the preferred explants were the top and middle stem internodes from in vitro micro-shoots of the E. urophylla × E. tereticornis hybrid. Modified Woody Plant Medium (mWPM) containing 0.025 mg·L-1 thidiazuron (TDZ) and 0.10 mg·L-1 indole-3-butyric acid (IBA) was used to induce multiple adventitious buds that allowed 85.6% shoot formation. The binary vector pBI121 carrying the neomycin phosphotransferase II (nptII) and β-glucuronidase (uidA) genes was applied for transformation. The preferred internodes were precultured for 0 to 3 d and infected with A. tumefaciens strain GV3101 grown to a bacterial density of 0.5 (OD600). Then, they were transferred to a co-culture medium supplemented with 50 μM acetosyringone (AS) and co-cultured for 2 d in the dark. The transgenic adventitious buds formed in regeneration medium, which was replaced by the same medium with a 2-wk subculture interval through kanamycin selection. Using the aforementioned method, transgenic plantlets can be obtained within 3 mo with a transformation frequency of 3.8%, which was verified by polymerase chain reaction amplification (PCR) and histochemical analysis of GUS activity. The constructed genetic transformation system will lay a foundation for mining gene functions and further molecular breeding of Eucalyptus.

Background High soil salinity seriously affects plant growth and development. Excessive salt ions mainly cause damage by inducing osmotic stress, ion toxicity, and oxidation stress. Casuarina equisetifolia is a highly salt-tolerant plant, commonly grown as wind belts in coastal areas with sandy soils. However, little is known about its physiology and the molecular mechanism of its response to salt stress. Results Eight-week-old C. equisetifolia seedlings grown from rooted cuttings were exposed to salt stress for varying durations (0, 1, 6, 24, and 168 h under 200 mM NaCl) and their ion contents, cellular structure, and transcriptomes were analyzed. Potassium concentration decreased slowly between 1 h and 24 h after initiation of salt treatment, while the content of potassium was significantly lower after 168 h of salt treatment. Root epidermal cells were shed and a more compact layer of cells formed as the treatment duration increased. Salt stress led to deformation of cells and damage to mitochondria in the epidermis and endodermis, whereas stele cells suffered less damage. Transcriptome analysis identified 10,378 differentially expressed genes (DEGs), with more genes showing differential expression after 24 h and 168 h of exposure than after shorter durations of exposure to salinity. Signal transduction and ion transport genes such as HKT and CHX were enriched among DEGs in the early stages (1 h or 6 h) of salt stress, while expression of genes involved in programmed cell death was significantly upregulated at 168 h, corresponding to changes in ion contents and cell structure of roots. Oxidative stress and detoxification genes were also expressed differentially and were enriched among DEGs at different stages. Conclusions These results not only elucidate the mechanism and the molecular pathway governing salt tolerance, but also serve as a basis for identifying gene function related to salt stress in C. equisetifolia.

Background Open tissue culture technique could be simplified by using different bacteriostatic agents. There is a great difference in the bacteriostatic effects of different antimicrobial agents on various explants. However, there is no report about the effective bacteriostatic agent for open tissue culture of Acacia auriculiformis. Results We carried out the bud induction trials under open conditions to screen out an effective antibacterial agent for open tissue culture of A. auriculiformis. The results showed that the suitable type and concentration of bacteriostatic agent was 0.2 g L−1 Chlorothalonil, and the suitable explant type was middle shoot section with leaves (the shoot section with third to fifth axillary bud). The treatment of 0.8 g L−1 Carbendazim for 3 min was the most suitable strategy for explants disinfection, and October was the best time for explants collection. The suitable bud induction medium was 1/8 MS + agar 7 g L−1 + Chlorothalonil 0.2 g L−1 + 6-BA 1.5 mg L−1, and the bud induction rate was 99.54%. Conclusions Our results revealed that Chlorothalonil is an effective bacteriostatic agent for bud induction of A. auriculiformis under open condition. These results would be very helpful for further establishment of open tissue culture technology for A. auriculiformis.

The WRKY transcription factors, a large family of proteins in plants, are involved in multiple developmental and biological processes including response to phytohormones and abiotic stress. However, little information is available regarding the WRKY family in Eucalyptus, which has been the most widely planted hardwood trees in tropical and subtropical areas. In this study, a total of 79 WRKY genes (named as EgrWRKY1-79) were identified from the Eucalyptus grandis genome and classified into three main groups according to the phylogenetic analysis, which was further supported by their gene structure and conserved motifs. Of which, 28 EgrWRKYs were involved in tandem duplication but none for segmental duplication, indicating that tandem duplication was the main cause for the expansion of WRKY gene family in E. grandis. Subsequently, expression profiles of EgrWRKY genes in eight different tissues and in response to treatments of three hormones (SA, JA, and BR) and two abiotic stresses (salt and cold) were analyzed. The results revealed that the EgrWRKY genes had differential expression in their transcript abundance and they were differentially expressed in response to plant hormones and salt and cold stresses, suggesting their contributions to plant developmental processes as well as abiotic stresses with the involvement of hormone signaling transduction. Taken together, these findings will increase our understanding of EgrWRKY gene family involved in abiotic stresses and hormone signaling transduction, and also will provide some stress-responsive candidate EgrWRKY genes for further characterization of their functions in Eucalyptus.

Brassinosteroids (BRs) are a group of plant hormones which play a pivotal role in modulating cell elongation, stress responses, vascular differentiation and senescence. In response to BRs, BRASSINAZOLE-RESISTANT (BZR) transcription factors (TFs) accumulate in the nucleus, where they modulate thousands of target genes and coordinate many biological processes, especially in regulating defense against biotic and abiotic stresses. In this study, 6 BZR TFs of Eucalyptus grandis (EgrBZR) from a genome-wide survey were characterized by sequence analysis and expression profiling against several abiotic stresses. The results showed that BZR gene family in Eucalyptus was slightly smaller compared to Populus and Arabidopsis, but all phylogenetic groups were represented. Various systematic in silico analysis of these TFs validated the basic properties of BZRs, whereas comparative studies showed a high degree of similarity with recognized BZRs of other plant species. In the organ-specific expression analyses, 4 EgrBZRs were expressed in vascular tissue indicating their possible functions in wood formation. Meanwhile, almost all EgrBZR genes showed differential transcript abundance levels in response to exogenously applied BR, MeJA, and SA, and salt and cold stresses. Besides, protein interaction analysis showed that all EgrBZR genes were associated with BR signaling directly or indirectly. These TFs were proposed as transcriptional activators or repressors of abiotic stress response and growth and development pathways of E. grandis by participating in BR signaling processes. These findings would be helpful in resolving the regulatory mechanism of EgrBZRs in stress resistance conditions but require further functional study of these potential TFs in Eucalyptus.

Gibberellins (GAs) play a key role in plant growth and development including cell elongation, cell expansion, and xylem differentiation. Eucalyptus are the world’s most widely planted hardwood trees providing fiber and energy. However, the roles of GAs in Eucalyptus remain unclear and their effects on xylem development remain to be determined. In this study, E. grandis plants were treated with 0.10 mg L−1 GA3 and/or paclobutrazol (PAC, a GA inhibitor). The growth of shoot and root were recorded, transverse sections of roots and stems were stained using toluidine blue, and expression levels of genes related to hormone response and secondary cell wall biosynthesis were analyzed by quantitative real-time PCR. The results showed that GA3 dramatically promoted the length of shoot and root, but decreased the diameter of root and stem. Exogenous GA3 application also significantly promoted xylem development in both stem and root. Expression analysis revealed that exogenous GA3 application altered the transcript levels of genes related to the GA biosynthetic pathway and GA signaling, as well as genes related to auxin, cytokinin, and secondary cell wall. These findings suggest that GAs may interact with other hormones (such as auxin and cytokinin) to regulate the expression of secondary cell wall biosynthesis genes and trigger xylogenesis in Eucalyptus plants.

Falcataria moluccana is an important economic tree and widely planted in subtropical Southern China. From July 2012 to June 2014, a disease with typical canker symptoms was observed on F. moluccana in the forests of Zengcheng city, Guangdong province. Two representative isolates (BL1331 and HD1332) from the diseased tissues were identified as Lasiodiplodia theobromae using morphological and molecular characterization. Phylogenetic analyses of combined ribosomal internal transcribed spacer region, β-tubulin and translation elongation factor 1-α placed the two isolates in a well-supported cluster with L. theobromae. Pathogenecity tests demonstrated that L. theobromae was virulent to F. moluccana. To our knowledge, this is the first detailed report of L. theobromae infecting F. moluccana in China.

The sucrose non-fermentation-related protein kinase (SnRK) is a kind of Ser/Thr protein kinase, which plays a crucial role in plant stress response by phosphorylating the target protein to regulate the interconnection of various signaling pathways. However, little is known about the SnRK family in Eucalyptus grandis. Thirty-four putative SnRK sequences were identified in E. grandis and divided into three subgroups (SnRK1, SnRK2 and SnRK3) based on phylogenetic analysis and the type of domain. Chromosome localization showed that SnRK family members are unevenly distributed in the remaining 10 chromosomes, with the notable exception of chromosome 11. Gene structure analysis reveal that 10 of the 24 SnRK3 genes contained no introns. Moreover, conserved motif analyses showed that SnRK sequences belonged to the same subgroup that contained the same motif type of motif. The Ka/Ks ratio of 17 paralogues suggested that the EgrSnRK gene family underwent a purifying selection. The upstream region of EgrSnRK genes enriched with different type and numbers of cis-elements indicated that EgrSnRK genes are likely to play a role in the response to diverse stresses. Quantitative real-time PCR showed that the majority of the SnRK genes were induced by salt treatment. Genome-wide analyses and expression pattern analyses provided further understanding on the function of the SnRK family in the stress response to different environmental salt concentrations.

VQ genes play important roles in plant development, growth, and stress responses. However, little information regarding the functions of VQ genes is available for Eucalyptus grandis. In our study, genome-wide characterization and identification of VQ genes were performed in E. grandis. Results showed that 27 VQ genes, which divided into seven sub-families (I&ndash, VII), were found, and all but two VQ genes showed no intron by gene structure and conserved motif analysis. To further identify the function of EgrVQ proteins, gene expression analyses were also developed under hormone treatments (brassinosteroids, methyl jasmonate, salicylic acid, and abscisic acid) and abiotic conditions (salt stress, cold 4 &deg, C, and heat 42 &deg, C). The results of a quantitative real-time PCR analysis indicated that the EgrVQs were variously expressed under different hormone treatments and abiotic stressors. Our study provides a comprehensive overview of VQ genes in E. grandis, which will be beneficial in the molecular breeding of E. grandis to promote its resistance to abiotic stressors, the results also provide a basis from which to conduct further investigation into the functions of VQ genes in E. grandis.

VQ genes play important roles in plant development, growth, and stress responses. However, little information regarding the functions of VQ genes is available for Eucalyptus grandis. In our study, genome-wide characterization and identification of VQ genes were performed in E. grandis. Results showed that 27 VQ genes, which divided into seven sub-families (I–VII), were found, and all but two VQ genes showed no intron by gene structure and conserved motif analysis. To further identify the function of EgrVQ proteins, gene expression analyses were also developed under hormone treatments (brassinosteroids, methyl jasmonate, salicylic acid, and abscisic acid) and abiotic conditions (salt stress, cold 4 °C, and heat 42 °C). The results of a quantitative real-time PCR analysis indicated that the EgrVQs were variously expressed under different hormone treatments and abiotic stressors. Our study provides a comprehensive overview of VQ genes in E. grandis, which will be beneficial in the molecular breeding of E. grandis to promote its resistance to abiotic stressors; the results also provide a basis from which to conduct further investigation into the functions of VQ genes in E. grandis.

Understanding the genetic diversity of Acacia melanoxylon is very important in species selection and improvement. The present study aimed to identify microsatellite markers and determine the genetic diversity of 45 preferred clones selected from 9 Chinese districts. Seventy-six simple sequence repeat (SSR) markers developed for other Acacia species were screened. Seventeen SSR markers showed polymorphic patterns and amplified 134 alleles. Polymorphism information content (PIC) values ranged from 0.044 to 0.911. The average allele number per locus ranged between 2 and 18, averaging 8.06. Nine SSR markers were highly informative, with PIC values above 0.60. These findings demonstrated that SSR markers could be used to differentiate A. melanoxylon genotypes. Cluster analysis using UPGMA separated the 45 clones into 3 distinct groups at a similarity coefficient of 0.72. The clone groups identified in this study would be useful in developing intraspecific hybrids to exploit hybrid vigor as well as for commercial cultivation and genetic base broadening. The DNA fingerprints obtained for each clone could be used for biodiversity conservation.

Background Open tissue culture technique could be simplified by using different bacteriostatic agents. There is a great difference in the bacteriostatic effects of different antimicrobial agents on various explants. However, there is no report about the effective bacteriostatic agent for open tissue culture of Acacia auriculiformis. Results We carried out the bud induction trials under open conditions to screen out an effective antibacterial agent for open tissue culture of A. auriculiformis. The results showed that the suitable type and concentration of bacteriostatic agent was 0.2 g L−1 Chlorothalonil, and the suitable explant type was middle shoot section with leaves (the shoot section with third to fifth axillary bud). The treatment of 0.8 g L−1 Carbendazim for 3 min was the most suitable strategy for explants disinfection, and October was the best time for explants collection. The suitable bud induction medium was 1/8 MS + agar 7 g L−1 + Chlorothalonil 0.2 g L−1 + 6-BA 1.5 mg L−1, and the bud induction rate was 99.54%. Conclusions Our results revealed that Chlorothalonil is an effective bacteriostatic agent for bud induction of A. auriculiformis under open condition. These results would be very helpful for further establishment of open tissue culture technology for A. auriculiformis.

An in vitro plant regeneration protocol via indirect organogenesis from morphogenetic callus was established for Casuarina cunninghamiana Miq. Effects of plant growth regulator NAA (naphthaleneacetic acid) and BAP (6-benzylaminopurine), sucrose and AgNO3 on callus induction, adventitious bud differentiation and shoot development were examined. Explants used were epicotyl fragments from 45-day-old seedlings. The largest callus (4.29 mm in diameter) was obtained after 1 month on a basic culture medium consisting of Murashige and Skoog ½ macro- and full strength micro- elements, Nitsch and Nitsch vitamins, supplemented with 0.54 μM NAA, 3.30 μM BAP, and 30 g L−1 sucrose. The calli were subcultured in the same medium above for 2 months. They were then cultured for another 2 months for adventitious bud differentiation and shoot development. The highest mean adventitious bud differentiation, number of shoots formed per callus and number of shoots ≥2 cm long per callus (47.50%, 27.38 and 4.75, respectively) were achieved on the above medium modified with NAA at 0.27 μM and supplemented with AgNO3 1 mg L−1. Shoots were successfully rooted without plant growth regulator and the rooted plantlets survived and grew normally. This protocol for in vitro plant regeneration provides a tool not only for vegetative propagation but also for plant genetic transformation and gene function studies of C. cunninghamiana.

Extreme events often expose vulnerabilities of socioeconomic infrastructures and point to directions of much-needed policy change. Integrated impact assessment of such events can lead to finding of sustainability principles. Southern and central China has for decades been undergoing a breakneck pace of socioeconomic development. In early 2008, a massive ice storm struck this region, immobilizing millions of people. The storm was a consequence of sustained convergence between tropical maritime and continental polar air masses, caused by an anomalously stable atmospheric general circulation pattern in both low and high latitudes. Successive waves of freezing rain occurred during a month period, coating southern and central China with a layer of ice 50–160 mm in thickness. We conducted an integrated impact assessment of this event to determine whether and how the context of socioeconomic and human-disturbed natural systems may affect the transition of natural events into human disasters. We found th...

International audience; Using epicotyl fragments of the actinorhizal tree Casuarina cunninghamiana and the disarmed strain ofAgrobacterium tumefaciens C58C1 (pGV2260) containing the pBIN19-35S-GUSINT binary vector, a method for the genetic transformation of C. cunninghamiana was established. Transformed cells were initially selected for 2 weeks on nutrient medium supplemented with kanamycin 20 mg L-1 during callus induction, and then subcultured with 50 mg L-1 until adventitious bud and shootdifferentiation. Different factors involved in the earlystages of the T-DNA transfer process were studied. Agrobacterium-mediated DNA delivery was most successfulwhen epicotyl fragments excised from 45-day-old seedlings were co-cultivated with an exponentially growingculture of A. tumefaciens at an OD600nm of 0.3, for 5 daysin the presence of 50 lM of acetosyringone. Kanamycinresistant calli were observed on 88.89 % of the explantsand transgenic rooted C. cunninghamiana plants wereobtained in 6 months. Evidence of genetic transformationwas demonstrated by ß-glucuronidase histochemical assaysand polymerase chain reaction analyses. The possibility toobtain transgenic nitrogen-fixing nodules after inoculationby the soil actinomycete Frankia was established.