Healthy Trees Research Articles

From Endophyte Community Analysis to Field Application: Control of Apple Canker (Neonectria ditissima) with Epicoccum nigrum B14-1

Apple canker, caused by Neonectria ditissima (Tul. and C. Tul.) Samuels and Rossman, is a major disease of apples (Malus domestica) worldwide. N. ditissima infects through natural and artificial wounds. Infected wood develops canker lesions which girdle branches and main stems causing reduced yield and tree death. N. ditissima is difficult to control; removal of inoculum (cankers) is expensive and therefore seldom practiced, whilst effective chemical products are being banned and no biocontrol products have been found to be effective against N. ditissima. This study used cues from a previous apple endophyte community analysis to isolate and test fungal endophytes belonging to the genus Epicoccum as potential endophytic biocontrol agents. Epicoccum nigrum B14-1, isolated from healthy apple trees, antagonised N. ditissima in vitro and reduced the incidence of N. ditissima infections of leaf scars by 46.6% and pruning wounds by 5.3% in field conditions at leaf fall. Autumn application of B14-1 conidia increased E. nigrum abundance in apple tissues at 10–20 days post-inoculation by ca. 1.5×, but this returned to control levels after one year. E. nigrum B14-1 did not cause detrimental effects on apple foliage, buds, fruit, or growth and could therefore present a new biocontrol agent to manage N. ditissima in commercial apple production.

Fungal and bacterial endophytes antagonistic to Phytophthora species causing root rot in Cinnamomum cassia

Endophytes were investigated for their potential to protect Cinnamomum cassia (cinnamon) from Phytophthora root rot. From healthy cinnamon trees in diseased plantations, 134 bacterial and fungal endophytes were isolated and screened in vitro for their ability to antagonise the root rot pathogens Phytophthora cinnamomi, P. multibullata and P. × vanyenensis. Seventeen endophytes exhibiting high levels of antagonism in vitro (more than 45%) were then tested in a glasshouse study for their ability to reduce the impact of Phytophthora infection in cinnamon seedlings. Trials using cinnamon seeds or seedlings inoculated with an endophyte and then infested with Phytophthora identified three endophytes expressing high levels of disease suppression (based on root damage reduction) and plant growth promotion. These were Penicillium citrinum, Xylaria curta and Clonostachys rosea. These endophytes can potentially be used in the biological control of root rot in cinnamon, but this must be explored further under field conditions.

Metabolites profiling of Ganoderma-infected oil palms rachis grown on tropical soils reveals choline phosphate and 2-oxoglutaramate as potential biomarkers in the disease detection

The use of gas chromatography–mass spectrometry (GC–MS) and multivariate statistics of principal component analysis (PCA) for metabolomics profiling of non-infected and Ganoderma boninense (G. boninense) infected oil palm rachises crude extracts grown on tropical soils have been evaluated. This combination has allowed us to quickly investigate the differences in metabolite variations between non-infected and infected oil palm. Two m/z values of biological samples from Oxisol soil Choline phosphate (184.072) and 2-Oxoglutaramate (146.0440) were found to be significantly higher in Ganoderma-infected oil palm rachis but absent in healthy samples. Another intriguing discovery is that the three m/z value of biological samples from Oxisol soils increased significantly while remaining absent in biological samples from Ultisol soil 129.066 (4-Amino-4-cyanobutanoic acid, 2-Amino-4-cyanobutanoic acid), 132.066 (5-Aminolevulinic acid) and 146.044 (2-Oxoglutaramate). By comparing healthy and Ganoderma-infected oil palm tree rachis samples, it was discovered the cluster distribution of metabolites detected to be present in between groups based on the first two components of multivariate analyses.

Bioecological Peculiarities and Economical Significance of Scolytus intricatus (Ratzeburg, 1837) and Trypodendron lineatum (A. G. Olivier, 1800) Damaging to Forest Trees in the South Slopes of the Greater Caucasus (Azerbaijan)

Bark beetles (Curculionidae, Scolytinae) are dangerous pests of forest and fruit trees both in the world and in Azerbaijan. Their activity results in partial or complete drying out, and a decrease in quantitative and qualitative indicators of the trees. These pests are even more dangerous during the years of mass reproduction. The bark beetles, which mainly infect old trees or trees weakened by biotic, abiotic, anthropogenic factors, attack young and healthy trees during mass reproduction. These pests, which pose a threat to forestry and horticulture, have not been studied in detail in Azerbaijan. The work was carried out by the author on the southern slopes of the Greater Caucasus of Azerbaijan (Balakan, Zagatala, Gakh, Sheki, Oguz, Gabala, Ismayilli, Shamakhi and Absheron) in 2013-2019 and 22 species of bark beetles were identified damaging to forest trees. The article provides information about the bioecological characteristics and economic importance of the oak bark beetle (Scolytus intricatus (Ratzeburg, 1837)) and striped ambrosia beetle (Trypodendron lineatum (A. G. Olivier, 1800)), which are widespread in the study area and cause serious damage to forest trees. T. lineatum is new to the fauna of Azerbaijan. As a result of the activity of these pests, industrially valuable trees, such as oak, chestnut, elm, beech, pine, fir are partially or completely destroyed by drying.

The current state of windbreaks of the Left Bank Forest Steppe of Ukraine

The relevance of the study is related to the need to determine the current state of windbreaks as a component of the forest-agrarian landscape of a particular region. The purpose of the study is to conduct a comprehensive assessment of windbreaks. During the study, data from remote sensing of the Earth using satellite imagery was utilised, which allowed for determining field parameters, the placement of the windbreak system, and their characteristics. Forest inventory works were conducted using commonly accepted methods in forest mensuration, with adjustments made specifically for windbreaks. The quality class of windbreaks was determined based on the percentage of healthy trees out of the total number, and the sanitary condition index was calculated according to established categories. The analysis of the obtained data clearly shows a decline in the quality sequence of common oak from 9 to 3 units within the plantations. The windbreaks were created using the method of oak nest planting, with oak nests placed at a spacing of 5.0×3.0 m and a total windbreak width of 15.0 m. Two additional rows of companion trees were introduced in the wide 5-metre alleys, and companion and shrub species were added within the nest rows. The analysis of the characteristics of windbreaks showed that they have protective heights ranging from 19.6 m to 23.4 m and provide reliable protection for adjacent agricultural fields. Based on the range of effective protective effects of windbreaks, it can be noted that the calculated indicators provide protection with a reliable safety margin of up to 17%. If there is a need to create new windbreaks using the nest planting method in the future, a more efficient scheme is proposed, which involves placing companion tree species in the outer rows to prevent the crowns of the inner rows from spreading towards the field. As a result of the obtained findings, it became possible to conduct a comprehensive expert assessment of the state of windbreaks according to the following criteria: forestry and inventory parameters, meliorative properties, and the sanitary condition index

Chloroplast genome draft assembly of Falcataria moluccana using hybrid sequencing technology

ObjectivesFalcataria moluccana, known locally as Sengon, is a fast-growing legume tree that is commonly planted in community forests of Java Island, Indonesia. However, the plantations face attacks of Boktor stem borer (Xystrocera festiva) and gall-rust disease (Uromycladium falcatariae) as major threats to its productivity. To control those pest and disease, it is necessary to grow resistant sengon clones, which are developed through tree improvement program, of which needs genetic and genomic information. This dataset was created to construct draft of sengon chloroplast genome and to study the evolution of sengon based on matK and rbcL barcode genes.Data descriptionGenomic DNA was extracted from leaf samples of one individual healthy tree in a private plantation. The DNA was sequenced using Illumina Novaseq 6000 (Novogen AIT, Singapore) for short-reads data, and MinION of Nanopore following manufacture’s protocols SQK-LSK110 for long-reads data. The 66,3 Gb short-reads and 12 Gb long-reads data were hybrid assembled and used to construct a 128.867 bp of F. moluccana chloroplast genome with a quadripartite structure, containing a pair of inverted repeats, a large single-copy and a small single-copy region. Phylogenetic tree constructed using matK and rbcL showed monophyletic origin of F. moluccana and other legume trees.

Spruce bark beetles (Ips typographus) cause up to 700 times higher bark BVOC emission rates compared to healthy Norway spruce (Picea abies)

Abstract. Biogenic volatile organic compound (BVOC) emissions from trees subjected to biotic stress are higher compared to healthy trees, and they may also have a different compound composition. This in turn affects atmospheric chemistry and can lead to either positive or negative feedback to the climate. Climate change favors the abundance of the European spruce bark beetle (Ips typographus) which attacks the bark of Norway spruce (Picea abies) trees, causing induced BVOC emissions from the trees as a response to the insect stress. Here, results are reported from a study analyzing the difference in emission rates between healthy and bark-beetle-infested Norway spruce trees, changes in emission rates over time since the infestation started, and differences in emission rates from bark-beetle-drilled entry and exit holes. Bark chamber measurements on both healthy and infested trees were performed during the summer of 2019 at Hyltemossa and Norunda research stations in Sweden. The measurements showed that induced BVOC emissions following the bark beetle infestation were dominated by entry hole emissions in the early growing season and exit hole emissions in the later season. The results showed a significant difference in emission rates between healthy and infested trees during both seasons. The seasonal average standardized BVOC emission rate of healthy trees was 32 ± 52 µg m−2 h−1 (mean ± standard deviation), while the average standardized BVOC emission rates of infested trees were 6700 ± 6900 and 2000 ± 1300 µg m−2 h−1 during the early and late season respectively. BVOC emission rates were highest at the start of the infestation and decreased exponentially with time, showing induced emission rates for up to 1 year after which the emission rates were similar to those from healthy bark. Constitutive needle emission rates from healthy trees were found to be 11 times higher than bark emissions from healthy trees. However, when Norway spruce trees were infested, the bark emission rates were instead 6 to 20 times higher than the needle emissions, causing substantial increases in the total tree BVOC emission rate. This could lead to high impacts on atmospheric processes, specifically the formation of secondary organic aerosols, which have a higher yield from some monoterpene compounds, which increased from infested trees.

Moisture Detection in Tree Trunks in Semiarid Lands Using Low-Cost Non-Invasive Capacitive Sensors with Statistical Based Anomaly Detection Approach.

This paper focuses on building a non-invasive, low-cost sensor that can be fitted over tree trunks growing in a semiarid land environment. It also proposes a new definition that characterizes tree trunks' water retention capabilities mathematically. The designed sensor measures the variations in capacitance across its probes. It uses amplification and filter stages to smooth the readings, requires little power, and is operational over a 100 kHz frequency. The sensor sends data via a Long Range (LoRa) transceiver through a gateway to a processing unit. Field experiments showed that the system provides accurate readings of the moisture content. As the sensors are non-invasive, they can be fitted to branches and trunks of various sizes without altering the structure of the wood tissue. Results show that the moisture content in tree trunks increases exponentially with respect to the measured capacitance and reflects the distinct differences between different tree types. Data of known healthy trees and unhealthy trees and defective sensor readings have been collected and analysed statistically to show how anomalies in sensor reading baseds on eigenvectors and eigenvalues of the fitted curve coefficient matrix can be detected.

Influence of Chrysoporthe deuterocubensis Canker Disease on the Chemical Properties and Durability of Eucalyptus urograndis against Wood Rotting Fungi and Termite Infestation

In this study, the effects of stem canker disease caused by Chrysoporthe deuterocubensis on the chemical properties and durability of a Eucalyptus hybrid (E. urophylla x E. grandis) were investigated. Eleven-year-old healthy and infected trees were collected. The samples were grouped into four different classes based on the infection severity: healthy (class 1), moderately infected (class 2), severely infected (class 3), and very severely infected (class 4). The changes in chemical properties were evaluated via chemical analysis and Fourier transform infrared spectroscopy (FTIR) analysis. A resistance test against fungal decay (Pcynoporus sanguineus and Caniophora puteana) and termite (Coptotermes curvignathus) was also performed. The results showed that reductions in cellulose and hemicellulose content from 53.2% to 45.4% and 14.1% to 13.9%, respectively, were observed in the infected samples. Meanwhile, the percentages of lignin and extractives increased from 18.1% to 20.5% and 14.6% to 20.2%, respectively. The resistance against fungi and termites varied between severity classes. Generally, infected wood behaved better than healthy wood in terms of durability against fungi and termites. The durability classes for both tests were significantly improved, from resistant to highly resistant and poor to moderately resistant, respectively. These results suggest that E. urograndis that is infected by C. deuterocubensis might have a better potential use in lumber production with regard to its durability and processing cost compared to pulp and paper products.

Declined symptoms in Myrica rubra: The influence of soil acidification and rhizosphere microbial communities

Declined symptoms seriously damaged the growth and development of Myrica rubra, a typical bayberry tree in southern of Zhejiang Province, China. However, knowledge on the mechanisms involved in this decline remains largely unknown. Here, we compared the physicochemical properties, microbial communities as well as metabolites in rhizospheric soil of healthy and declined Myrica rubra trees from four orchards. We found that planting bayberry aggravated soil acidification in all orchards. Surprisingly, compared with healthy trees, the pH decreased and the correlation between nutrients (N, P, K) and metal elements (Cu, Cr, Ni, As, Cd) changed significantly (p < 0.01) in the rhizospheric soil of declined trees. Moreover, bacteria affiliated with Acidobacteriota, Firmicutes, Rozellomycota and Mucoromycota showed considerable enrichment; whereas in genus level, the relative abundance of Acidothermus, Trichoderma, Geminibasidium decreased by 2.9%, 6.7%, and 33.9%, respectively. Besides, the connection in bacterial or fungal communities became more complicated but unstable. These discoveries along with the upregulation of myristic acid and cinnamic acid via metabolome analysis further indicated the aggravated soil acidification and the varied microbial communities and metabolites that resulted in the declined symptoms in Myrica rubra. This study provides new insights into the causes of declined in bayberry trees and can assist the prevention and treatment of declined trees basing on the plant-soil-microbe interactions.

Effect of Huanglongbing on the Volatile Organic Compound Profile of Fruit Juice and Peel Oil in ‘Ray Ruby’ Grapefruit

Along with orange and mandarin, grapefruit production in Florida has declined sharply due to Huanglongbing (HLB), or citrus greening disease, caused by Candidatus Liberibacter asiaticus (CLas). HLB affects the volatile profiles of juice and peel oil in oranges, but there is limited information on grapefruit. In this research, 'Ray Ruby' grapefruit were harvested in 2020 and 2021 from healthy (HLB-) and HLB-affected (HLB+) trees. Peel oil was extracted by hydrodistillation, and the volatiles were analyzed by direct injection of the oil samples into gas chromatography-mass spectrometry (GC-MS). Volatiles in the juice were analyzed by headspace (HS)-solid-phase microextraction (SPME) coupled with GC-MS. HLB significantly altered the volatile profiles of peel oil and juice in 'Ray Ruby' grapefruit. Juice samples of HLB+ fruits had lower decanal, nonanal, and octanal, important citrus juice flavor compounds. HLB+ samples also showed reduced content of nonterpene compounds, other aliphatic and terpene aldehydes, and terpene ketones. Ethanol, acetaldehyde, ethyl acetate, and ethyl butanoate were increased in HLB+ juice samples, indicating an HLB-induced stress response. The most abundant compounds D-limonene and β-caryophyllene, as well as other sesquiterpenes, were increased in HLB+ juice and peel oil samples. On the other hand, the oxidative/dehydrogenated terpenes were increased by HLB in peel oil but decreased in the juice sample. Nootkatone, the key grapefruit volatile was consistently reduced by HLB in both peel oil and juice samples. The impact of HLB on nootkatone deteriorated the quality of both juice and peel oil in grapefruits.

PM 7/31 (2) Citrus tristeza virus

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Assessing the detectability of European spruce bark beetle green attack in multispectral drone images with high spatial- and temporal resolutions

Detecting disease- or insect-infested forests as early as possible is a classic application of remote sensing. Under conditions of climate change and global warming, outbreaks of the European spruce bark beetle (Ips typographus, L.) are threatening spruce forests and the related timber industry across Europe, and early detection of infestations is important for damage control. Infested trees without visible discoloration (green attack) have been identified using multispectral images, but how early green attacks can be detected is still unknown. This study aimed to determine when infested trees start to show an abnormal spectral response compared with healthy trees, and to quantify the detectability of infested trees during the infestation process. Pheromone bags were used to attract bark beetles in a controlled experiment, and subsequent infestations were assessed in the field on a weekly basis. In total, 977 trees were monitored, including 208 attacked trees. Multispectral drone images were obtained before and during the insect attacks, representing different periods of infestation. Individual tree crowns (ITC) were delineated by marker-controlled watershed segmentation, and the average reflectance of ITCs was analyzed based on the duration of infestation. The detectability of green attacks and driving factors were examined. We propose new Multiple Ratio Disease–Water Stress Indices (MR-DSWIs) as vegetation indices (VI) for detecting infestations. We defined a VI range of 5–95% as a healthy tree, and a VI value outside that range as an infested tree. Detection rates using multispectral images were always higher than discoloration rates observed in the field, and the newly proposed MR-DSWIs detected more infested trees than the established VIs. Infestations were detectable at 5 and 10 weeks after an attack at a rate of 15% and 90%, respectively, from the multispectral drone images. Weeks 5–10 of infestation therefore represent a suitable period for using the proposed methodology to map infestation at an early stage.

First report of Lasiodiplodia mahajangana causing canker of mango (Mangifera indica) in Puerto Rico.

Mango originated in the Indo-Burmese region (Alphonse de Candolle, 1885). In the Caribbean, Puerto Rico currently produces and exports mangoes to the United States and Europe. Globally, an important disease affecting mango production is dieback, caused by fungi belonging to Botryosphaeriaceae family. During a one-year survey from 2019 to 2020, conducted at the mango germplasm collection of the Agricultural Experiment Station of the University of Puerto Rico, located at Juana Díaz, PR, symptoms of dieback were observed in shoots, descending towards the woody part, and vascular necrosis. We sampled bimonthly, 35 Keitt trees for one year. At the end of the evaluation, we detected that a 74% disease incidence was caused by Botryosphaeriaceae. Lasiodiplodia mahajangana (syn. L. caatinguensis) was associated with 4% disease incidence. In addition, we identified other Botryosphaeriaceae species causing 70% of disease incidence. To identify the causal agent, sections of symptomatic tissue (4mm2) were surface disinfected by immersion in 70% ethanol, 10% sodium hypochlorite and rinsed with sterile-distilled water for 1 minute at each solution. Sections were transferred to petri dishes containing potato dextrose agar acidified with 85% lactic acid (aPDA). Ten fungal isolates were obtained with similar morphological characteristics such as colony color and texture, after 12 days. Of these, one representative (isolate 17) was selected and identified as L. mahajangana (Lm) using morphological parameters and sequences of four nuclear genes (Zhang, W. et al., 2021). In aPDA, Lm colonies showed sparse and slow-growing aerial mycelium with dark gray-greenish color at the center and light gray edges. Black pycnidia were observed after 15 days of incubation at 28°C and dark conditions. Hyaline, ovoid to ellipsoid immature conidia (n=40) with average size of 22 µm long and 12 µm wide were observed. Mature bicellular pigmented conidia (n=40) had longitudinal striate and its average size was 23 µm long and 12 µm wide. Internal transcribed spacer (ITS), β-tubulin (βtub), elongation factor 1-alpha (EF1-α) and large ribosomal subunit (LSU) genetic regions were amplified by PCR from the original and pathogenicity test recovered isolates. Sequences of PCR products were compared with NCBI database BLAST tool with other Lm sequences. Sequence accession numbers of the four genetic regions of Lm are as follows: OL375401 and OL375402 for the ITS region; OL405579 and OL405580 for β-tubulin; OL455922 and OL455923 for EF1-α; and OL375648 and OL375649 for LSU. All the sequences were grouped with the ex-type CMM1325 of Lm (BS=84). Pathogenicity tests were performed on 6-month-old mango trees of cv. Keitt. Three healthy trees were inoculated with 5 mm mycelial disks of Lm, on stems, with and without wounds. Controls were inoculated with aPDA disks only. Inoculated trees were covered for 3 days with plastic bags, keeping them in conditions of high relative humidity with constant irrigation, temperature of 28°C, and 12 hours of light and 12 hours of darkness for 12 days. Twelve days after inoculation, Lm isolates caused stem necrosis and canker, with differences in lesion severity from 2 to 17 mm2 with wound, and 0 to 6 mm2 without wound. Untreated controls showed no symptoms of canker. Lasiodiplodia mahajangana was re-isolated from diseased stems fulfilling Koch's postulates, and a sequence of the recovered isolate from the pathogenicity test was compared and included in the phylogenetic analysis. Lasiodiplodia mahajangana has been reported to cause stem-end rot of mango in Malaysia (Li, L. et. al., 2021). To our knowledge, this is the first report of Lm causing canker of mango in Puerto Rico. Knowing L. mahajangana as a new pathogen that causes canker of mango is important to establish an adequate and effective control management of this disease in mango producing countries worldwide.

The Effect of the Tree Dieback Process on the Mechanical Properties of Pine (Pinus sylvestris L.) Wood

As a result of the progressing climate changes, there is an increase in the volume of pine deadwood harvested each year from Polish forests. Its presence is an important part of the forest ecosystem; however, there are some indications that the material obtained from dying trees can be characterized by lower quality and properties. Taking into account the growing issue of tree dieback, the volume of pine wood annually harvested in Poland, and the importance of wooden products from an economic standpoint, preliminary research aimed at recognizing the process and its effect on the mechanical properties was conducted. Model trees in Brzeg Forest District were selected based on the crown defoliation. The properties of wood obtained from trees representing three different categories of soundness were determined according to the relevant standards. Based on the results of density, modulus of elasticity, bending strength, and compressive strength, it was found that there were statistically significant differences in wood quality depending on the condition of the tree. The results were particularly interesting in the case of compressing strength, where a healthy tree of lower density showed a similar strength to a dying tree with a much higher density.

Stable background tree mortality in mature and old-growth forests in western Washington (NW USA)

Increasing rates of tree mortality have been observed in recent decades for all major forest types worldwide. Elevated mortality has been linked to drought and high temperatures resulting from human modification of the atmosphere and climate. Older forests in the Pacific Northwest are globally significant as carbon sinks and may serve as refugia in the face of wildfires and climate change. We examined temporal patterns of tree mortality in mature and old-growth forests in national park units in western Washington, U.S.A, over the period 2008 to 2018, to evaluate whether the broader pattern of increasing tree mortality applies there. We also used individual-tree models of mortality to seek links between drought and tree mortality, while considering processes internal to forest stands such as competition. The annualized rate of tree mortality for the entire period generally did not exceed the expected, background rate of 1 %. The mean was ≤ 1.0 % for saplings (2.5 to 12.6 cm dbh) for 60 % of plots, for small trees (12.7 to 76.1 cm dbh) for 66 % of plots, and for large trees (greater than76.1 cm dbh) for 92 % of plots. 95 % confidence intervals wholly exceeded 1.0 % yr−1 only for small size classes in a minority of plots (saplings, 7 % of plots, and small trees, 11 % of plots). Comparing the first and second 5-year segments of the observation period, there were no clear trends of increasing mortality for any of the size classes. We tested generalized linear mixed-effects models based on the Gompit link function, using predictive factors related to drought, tree-to-tree competition, individual tree vigor, and tree species shade tolerance. We found only an index of tree vigor to consistently predict probability of tree mortality. In one model, anomaly of vapor pressure deficit in winter months was significant, but the sign of the effect did not implicate drought (i.e., mortality probability increased with moisture). These results show that, at least up to 2018, healthy trees within old-growth, protected forests in the Pacific Northwest may be resilient to current climatic changes, highlighting the importance of continued conservation and protection of these increasingly rare ecosystems and carbon stores. The occurrence of extreme climatic events following our study period emphasizes the need for continued observation and analysis to facilitate management for protection of refugia and migration corridors.

How Tree Decline Varies the Anatomical Features in Quercus brantii

Drought has serious effects on forests, especially semi-arid and arid forests, around the world. Zagros Forest in Iran has been severely affected by drought, which has led to the decline of the most common tree species, Persian oak (Quercus brantii). The objective of this study was to determine the effects of drought on the anatomical structure of Persian oak. Three healthy and three declined trees were sampled from each of two forest sites in Ilam Forest. Discs were cut at breast height, and three sapwood blocks were taken near the bark of each tree for sectioning. The anatomical characteristics measured included fiber length (FL), fiber wall thickness (FWT), number of axial parenchymal cells (NPC), ray number (RN), ray width (RW), and number of calcium oxalate crystals. Differences between healthy and declined trees were observed in the abundance of NPC and in RN, FL, and FWT, while no differences occurred in the number of oxalate crystals. The decline had uncertain effects on the FL of trees from sites A and B, which showed values of 700.5 and 837.3 μm compared with 592.7 and 919.6 μm in healthy trees. However, the decline resulted in an increase in the FWT of trees from sites A and B (9.33 and 11.53 μm) compared with healthy trees (5.23 and 9.56 μm). NPC, RN, and RW also increased in declined individuals from sites A and B (28.40 and 28.40 mm−1; 41.06 and 48.60 mm−1; 18.60 and 23.20 μm, respectively) compared with healthy trees (20.50 and 19.63 mm−2; 31.60 and 28.30 mm−2; 17.93 and 15.30 μm, respectively). Thus, drought caused measurable changes in the anatomical characteristics of declined trees compared with healthy trees.

Early Detection of Dendroctonus valens Infestation at Tree Level with a Hyperspectral UAV Image

The invasive pest Dendroctonus valens has spread to northeast China, causing serious economic and ecological losses. Early detection and disposal of infested trees is critical to prevent its outbreaks. This study aimed to evaluate the potential of an unmanned aerial vehicle (UAV)-based hyperspectral image for early detection of D. valens infestation at the individual tree level. We compared the spectral characteristics of Pinus tabuliformis in three states (healthy, infested and dead), and established classification models using three groups of features (reflectance, derivatives and spectral vegetation indices) and two algorithms (random forest and convolutional neural network). The spectral features of dead trees were clearly distinct from those of the other two classes, and all models identified them accurately. The spectral changes of infested trees occurred mainly in the visible region, but it was difficult to distinguish infested from healthy trees using random forest classification models based on reflectance and derivatives. The random forest model using spectral vegetation indices and the convolutional neural network model performed better, with an overall accuracy greater than 80% and a recall rate of infested trees reaching 70%. Our results demonstrated the great potential of hyperspectral imaging and deep learning for the early detection of D. valens infestation. The convolutional neural network proposed in this study can provide a reference for the automatic detection of early D. valens infestation using UAV-based multispectral or hyperspectral images in the future.

Downregulation of HbFPS1 affects rubber biosynthesis of Hevea brasiliensis suffering from tapping panel dryness.

Tapping panel dryness (TPD) is a century-old problem that has plagued the natural rubber production of Hevea brasiliensis. TPD may result from self-protective mechanisms of H. brasiliensis in response to stresses such as excessive hormone stimulation and mechanical wounding (bark tapping). It has been hypothesized that TPD impairs rubber biosynthesis; however, the underlying mechanisms remain poorly understood. In the present study, we firstly verified that TPD-affected rubber trees exhibited lower rubber biosynthesis activity and greater rubber molecular weight compared to healthy rubber trees. We then demonstrated that HbFPS1, a key gene of rubber biosynthesis, and its expression products were downregulated in the latex of TPD-affected rubber trees, as revealed by transcriptome sequencing and iTRAQ-based proteome analysis. We further discovered that the farnesyl diphosphate synthase HbFPS1 could be recruited to small rubber particles by HbSRPP1 through protein-protein interactions to catalyze farnesyl diphosphate (FPP) synthesis and facilitate rubber biosynthesis initiation. FPP content in the latex of TPD-affected rubber trees was significantly decreased with the downregulation of HbFPS1, ultimately resulting in abnormal development of rubber particles, decreased rubber biosynthesis activity, and increased rubber molecular weight. Upstream regulator assays indicated that a novel regulator, MYB2-like, may be an important regulator of downregulation of HbFPS1 in the latex of TPD-affected rubber trees. Our findings not only provide new directions for studying the molecular events involved in rubber biosynthesis and TPD syndrome and contribute to rubber management strategies, but also broaden our knowledge of plant isoprenoid metabolism and its regulatory networks.

Suppression of Meloiodogyne incognita (Tylenchida: Heteroderidae) and Tylenchulus semipenterans (Tylenchida: Tylenchulidae) using Tilapia fish powder and plant growth promoting rhizobacteria in vivo and in vitro

Plant-parasitic nematodes (PPNs) in particular those belonging to the genera Meloidogyne and Tylenchulus are a limiting factor in the production of many plants. In this research, we investigate a strategy for the control of PPNs in vivo and in vitro. The purpose of this research is to evaluate different concentrations of Tilapia fish powder (TFP) and of (in the form of BECTO Grow Roots®) against egg hatching and second-stage juveniles of Meloiodogyne incognita (Tylenchida: Heteroderidae) under laboratory condition. We also assessed the effect of TFP and on M. incognita and Tylenchulus semipenterans (Tylenchida: Tylenchulidae) reproduction. Our data showed that the percentage of egg hatching inhibition ranged from 8.03 to 53.21% and 42.25 to 75.12% after five days of treatment at different concentrations of TFP and PGPR, respectively compared with the control. The percentage of M. incognita J2 mortality increase significantly (p ≤ 0.05) from 52.1 to 86.7 and 44.6 to 92.3% after seven days of treatment at different concentrations of TFP and PGPR, respectively compared with control. Under greenhouse conditions, a remarkable (p ≤ 0.05) increase in plant growth parameters was observed in cucumber plants that received TFP and In the field experiment, the highest reduction of T. semipeneterans density was TFP + PGPR This holds both for healthy and infected trees. Healthy navel orange (HNO) + PGPR + TFP achieved maximum enhancement in orange weight/tree compared to other treatments. Our study recommended TFP and PGPR not only because of their potential against nematodes, but also because of their safety for humans, mammals and non-target organisms.