Lecanosticta Acicola Research Articles

Searching the Pinus taeda foliar mycobiome for emerging pathogens among brown spot needle blight and needlecast outbreaks in the Southeast United States

Needle pathogens cause the discoloration, death, or premature abscission of conifer foliage, reducing growth and vigor, and repeated defoliation may eventually result in tree mortality. Since 2016, forest managers in the southeast United States have reported an increasing scale, frequency, and severity of needle disease outbreaks on the region’s principal timber species, loblolly pine (Pinus taeda L.). These recent outbreaks are raising concern throughout the region, as needle diseases are not traditionally considered a threat to P. taeda. Lecanosticta acicola (Thum.) Syd., the native causal agent of brown-spot needle blight, has been recovered from some outbreaks, however, the full array of fungi associated with symptoms has not been explored. In this research, P. taeda foliage was collected from affected stands throughout the region and analyzed to identify fungi associated with needle disease symptoms. We employed targeted molecular diagnostics, to confirm the presence or absence of L. acicola, and DNA metabarcoding, to characterize the foliar mycobiome and screen for other potential pathogens. Lecanosticta acicola was detected among symptomatic needles from multiple states, particularly in western portions of the P. taeda range but rarely from stands in eastern states. Metabarcoding revealed pathogens in needles and identified associations among pathogenic fungi, differing symptoms, including needle discoloration and necrosis, and signs of fungal fruiting bodies. Additionally, the fungal community of needles varied with patterns of symptom presentation. This study is the first regionwide assessment of fungi associated with recent large-scale needle disease outbreaks on P. taeda and identifies multiple pathogens that warrant further study.

Genomics of the expanding pine pathogen Lecanosticta acicola reveals patterns of ongoing genetic admixture.

Lecanosticta acicola is a fungal pathogen causing severe defoliation, growth reduction, and even death in more than 70 conifer species. Despite the increasing incidence of this species, little is known about its population dynamics. Two divergent lineages have been described that have now been found together in regions of France and Spain, but it is unknown how these mixed populations evolve. Here we present the first reference genome for this important plant pathogenic fungi and use it to study the population genomics of 70 isolates from an affected forest in the north of Spain. We find signs of introgression between the two main lineages, indicating that active mating is occurring in this region which could propitiate the appearance of novel traits in this species. We also study the phenotypic differences across this population based on enzymatic activities on 20 compounds.

Physiological, metabolic and hormonal responses of two Pinus spp. with contrasting susceptibility to brown-spot needle blight disease.

Needle blights are serious fungal diseases affecting European natural and planted pine forests. Brown-spot needle blight (BSNB) disease, caused by the fungus Lecanosticta acicola, causes canopy defoliation and severe productivity losses, with consequences depending on host susceptibility. To gain new insights into BSNB plant-pathogen interactions, constitutive and pathogen-induced traits were assessed in two host species with differential disease susceptibility. Six-month-old Pinus radiata D. Don (susceptible) and Pinus pinea L. (more resistant) seedlings were needle inoculated with L. acicola under controlled conditions. Eighty days after inoculation, healthy-looking needles from symptomatic plants were assessed for physiological parameters and sampled for biochemical analysis. Disease progression, plant growth, leaf gas-exchanges and biochemical parameters were complemented with hormonal and untargeted primary metabolism analysis and integrated for a holistic analysis. Constitutive differences between pine species were observed. Pinus pinea presented higher stomatal conductance and transpiration rate and higher amino and organic acids, abscisic acid as well as putrescine content than P. radiata. Symptoms from BSNB disease were observed in 54.54% of P. radiata and 45.45% of P. pinea seedlings, being more pronounced and generalized in P. radiata. For both species, plant height, sub-stomatal CO2 concentration and water-use efficiency were impacted by infection. In P. radiata, total soluble sugars, starch and total flavonoids content increased after infection. No differences in hormone content after infection were observed. However, secondary metabolism was induced in P. pinea visible through total phenolics, flavonoids and putrescine accumulation. Overall, the observed results suggest that P. pinea constitutive and induced traits may function as two layers of a defence strategy which contributed to an increased BSNB resistance in comparison with P. radiata. This is the first integrative study linking plant physiological and molecular traits in Pinus-Lecanosticta acicola pathosystem, contributing to a better understanding of the underlying resistance mechanisms to BSNB disease in pines.

Silvicultural treatments improve pest and disease conditions of white pine (Pinus strobus) residual trees and regeneration

Managing multiple forest insect pests and diseases is challenging. For example, in eastern white pine (Pinus strobus) stands whereas partial shading and high seedling density is encouraged to reduce damage by white pine blister rust (Cronartium ribicola) and white pine weevil (Pissodes strobi), dense conditions in the understory may increase damage by foliar diseases such as brown spot needle blight (Lecanosticta acicola) and Caliciopsis canker (Caliciopsis pinea). We evaluated the effect of silvicultural treatments, shelterwoods (residual basal area < 18 m2 ha−1), low density thinnings (residual basal area ≤ 14 m2 ha−1), patch cuts (1.2 ha openings), and untreated controls on damage by these insect pest and diseases in residual overstory trees and regeneration. Shelterwoods and low density thinnings provided a good balance of some shading and reduced stem density, which resulted in less weevil damage and foliar disease severity. Crown condition and quality of regeneration was better in all treatments compared to unmanaged controls. Shelterwoods, low density thinnings and patch cuts have the added benefit on increasing seral habitat, resulting in greater songbird diversity.

The potential global distribution of an emerging forest pathogen, Lecanosticta acicola, under a changing climate

Brown spot needle blight (BSNB), caused by Lecanosticta acicola (Thüm.) Syd., is an emerging forest disease of Pinus species originating from North America and introduced to Europe and Asia. Severity and spread of the disease has increased in the last two decades in North America and Europe as a response to climate change. No modeling work on spread, severity, climatic suitability, or potential distribution has been done for this important emerging pathogen. This study utilizes a global dataset of 2,970 independent observations of L. acicola presence and absence from the geodatabase, together with Pinus spp. distribution data and 44 independent climatic and environmental variables. The objectives were to (1) identify which bioclimatic and environmental variables are most influential in the distribution of L. acicola; (2) compare four modeling approaches to determine which modeling method best fits the data; (3) examine the realized distribution of the pathogen under climatic conditions in the reference period (1971–2000); and (4) predict the potential future global distribution of the pathogen under various climate change scenarios. These objectives were achieved using a species distribution modeling. Four modeling approaches were tested: regression-based model, individual classification trees, bagging with three different base learners, and random forest. Altogether, eight models were developed. An ensemble of the three best models was used to make predictions for the potential distribution of L. acicola: bagging with random tree, bagging with logistic model trees, and random forest. Performance of the model ensemble was very good, with high precision (0.87) and very high AUC (0.94). The potential distribution of L. acicola was computed for five global climate models (GCM) and three combined pathways of Shared Socioeconomic Pathway (SSP) and Representative Concentration Pathway (SSP-RCP): SSP1-RCP2.6, SSP2-RCP4.5, and SSP5-RCP8.5. The results of the five GCMs were averaged on combined SSP-RCP (median) per 30-year period. Eight of 44 studied factors determined as most important in explaining L. acicola distribution were included in the models: mean diurnal temperature range, mean temperature of wettest quarter, precipitation of warmest quarter, precipitation seasonality, moisture in upper portion of soil column of wettest quarter, surface downwelling longwave radiation of driest quarter, surface downwelling shortwave radiation of warmest quarter and elevation. The actual distribution of L. acicola in the reference period 1971–2000 covered 5.9% of Pinus spp. area globally. However, the model ensemble predicted potential distribution of L. acicola to cover an average of 58.2% of Pinus species global cover in the reference period. Different climate change scenarios (five GCMs, three SSP-RCPs) showed a positive trend in possible range expansion of L. acicola for the period 1971–2100. The average model predictions toward the end of the century showed the potential distribution of L. acicola rising to 62.2, 61.9, 60.3% of Pinus spp. area for SSP1-RCP2.6, SSP2-RCP4.5, SSP5-RCP8.5, respectively. However, the 95% confidence interval encompassed 35.7–82.3% of global Pinus spp. area in the period 1971–2000 and 33.6–85.8% in the period 2071–2100. It was found that SSP-RCPs had a little effect on variability of BSNB potential distribution (60.3–62.2% in the period 2071–2100 for medium prediction). In contrast, GCMs had vast impact on the potential distribution of L. acicola (33.6–85.8% of global pines area). The maps of potential distribution of BSNB will assist forest managers in considering the risk of BSNB. The results will allow practitioners and policymakers to focus surveillance methods and implement appropriate management plans.

Genetic Diversity of Lecanosticta acicola in Pinus Ecosystems in Northern Spain.

Lecanosticta acicola is one of the most damaging species affecting Pinus radiata plantations in Spain. Favourable climatic conditions and unknown endogenous factors of the pathogen and host led to a situation of high incidence and severity of the disease in these ecosystems. With the main aim of understanding the factors intrinsic to this pathogenic species, a study of the population structure in new established plantations with respect to older plantations was implemented. The genetic diversity, population structure and the ability of the pathogen to spread was determined in Northern Spain (Basque Country), where two thirds of the total Pinus radiata plantations of Spain are located. From a total of 153 Lecanosticta acicola isolates analysed, two lineages were present; the southern lineage, which was prevalent, and the northern lineage, which was scarce. A total of 22 multilocus genotypes were detected with a balanced composition of both mating types and evidence for sexual reproduction. In addition to the changing environmental conditions enhancing disease expression, the complexity and diversity of the pathogen will make it difficult to control and to maintain the wood productive system fundamentally based on this forest species.

The increasing threat to European forests from the invasive foliar pine pathogen, Lecanosticta acicola

European forests are threatened by increasing numbers of invasive pests and pathogens. Over the past century, Lecanosticta acicola, a foliar pathogen predominantly of Pinus spp., has expanded its range globally, and is increasing in impact. Lecanosticta acicola causes brown spot needle blight, resulting in premature defoliation, reduced growth, and mortality in some hosts. Originating from southern regions of North American, it devastated forests in the USA’s southern states in the early twentieth century, and in 1942 was discovered in Spain.Derived from Euphresco project ‘Brownspotrisk,’ this study aimed to establish the current distribution of Lecanosticta species, and assess the risks of L. acicola to European forests. Pathogen reports from the literature, and new/ unpublished survey data were combined into an open-access geo-database (http://www.portalofforestpathology.com), and used to visualise the pathogen’s range, infer its climatic tolerance, and update its host range. Lecanosticta species have now been recorded in 44 countries, mostly in the northern hemisphere. The type species, L. acicola, has increased its range in recent years, and is present in 24 out of the 26 European countries where data were available. Other species of Lecanosticta are largely restricted to Mexico and Central America, and recently Colombia.The geo-database records demonstrate that L. acicola tolerates a wide range of climates across the northern hemisphere, and indicate its potential to colonise Pinus spp. forests across large swathes of the Europe. Preliminary analyses suggest L. acicola could affect 62% of global Pinus species area by the end of this century, under climate change predictions.Although its host range appears slightly narrower than the similar Dothistroma species, Lecanosticta species were recorded on 70 host taxa, mostly Pinus spp., but including, Cedrus and Picea spp. Twenty-three, including species of critical ecological, environmental and economic significance in Europe, are highly susceptible to L. acicola, suffering heavy defoliation and sometimes mortality. Variation in apparent susceptibility between reports could reflect variation between regions in the hosts’ genetic make-up, but could also reflect the significant variation in L. acicola populations and lineages found across Europe. This study served to highlight significant gaps in our understanding of the pathogen’s behaviour.Lecanosticta acicola has recently been downgraded from an A1 quarantine pest to a regulated non quarantine pathogen, and is now widely distributed across Europe. With a need to consider disease management, this study also explored global BSNB strategies, and used Case Studies to summarise the tactics employed to date in Europe.

Genetic structure of the pine needle pathogen Lecanosticta acicola in Lithuania and northern Poland

AbstractBrown spot needle blight, a disease of pine trees caused by the pathogenic fungus Lecanosticta acicola, has been known in Lithuania since 2009 and in Poland since 2014, but data on the distribution and population genetics of this needle pathogen were lacking. In order to investigate the genetic diversity, population structure and reproductive mode of L. acicola, 93 isolates were isolated from Pinus mugo needles in 2017–2019 and analysed using 11 microsatellite and two mating‐type markers. This study revealed 47 unique multilocus haplotypes among all investigated isolates; two genetically distinct populations of L. acicola (LIT‐E and LIT‐W) were identified in Lithuania and one population (POL‐N) in the coastal region of northern Poland. The most genetically diverse population was the LIT‐E population occurring in the eastern continental part of Lithuania, followed by the LIT‐W population spreading along the western Baltic Sea coast. All populations in both countries are characterized by low genetic diversity and contain clones, with the northern Polish population having the lowest mean genetic diversity and the greatest clonal fraction. Both mating types are present in the Lithuanian populations, demonstrating that sexual reproduction is possible, whereas only one mating type is present in the Polish population. However, the sexual stage (teleomorph) has not yet been found on infected needles, and asexual reproduction predominates. High gene flow from the eastern Lithuanian population to the northern Poland population was found, suggesting that the Polish coastal population may have been introduced from the central part of Lithuania and did not spread naturally along the Baltic Sea coast from the western Lithuanian population.

Diversity, migration routes, and worldwide population genetic structure of Lecanosticta acicola, the causal agent of brown spot needle blight.

Lecanosticta acicola is a pine needle pathogen causing brown spot needle blight that results in premature needle shedding with considerable damage described in North America, Europe, and Asia. Microsatellite and mating type markers were used to study the population genetics, migration history, and reproduction mode of the pathogen, based on a collection of 650 isolates from 27 countries and 26 hosts across the range of L. acicola. The presence of L. acicola in Georgia was confirmed in this study. Migration analyses indicate there have been several introduction events from North America into Europe. However, some of the source populations still appear to remain unknown. The populations in Croatia and western Asia appear to originate from genetically similar populations in North America. Intercontinental movement of the pathogen was reflected in an identical haplotype occurring on two continents, in North America (Canada) and Europe (Germany). Several shared haplotypes between European populations further suggests more local pathogen movement between countries. Moreover, migration analyses indicate that the populations in northern Europe originate from more established populations in central Europe. Overall, the highest genetic diversity was observed in south‐eastern USA. In Europe, the highest diversity was observed in France, where the presence of both known pathogen lineages was recorded. Less than half of the observed populations contained mating types in equal proportions. Although there is evidence of some sexual reproduction taking place, the pathogen spreads predominantly asexually and through anthropogenic activity.

Lecanosticta pharomachri and Its Newly Discovered Sexual State Causing a Serious Needle Disease of Pinus spp. in Colombia.

Brown spot needle blight (BSNB), caused by the fungal pathogen Lecanosticta acicola, is a well-known disease of Pinus spp. in several northern hemisphere countries. In the southern hemisphere, this disease has been reported only in Colombia and, apart from a single report of severe defoliation of Pinus radiata plantations in the early 1980s, has not caused serious damage in this country. An outbreak of a disease resembling BSNB on Mesoamerican Pinus spp. grown in Colombia has raised concern that L. acicola may have reemerged as a pathogen. DNA sequence-based analyses for the internal transcribed spacers, translation elongation factor 1-α and RNA polymerase II second largest subunit regions showed that the outbreaks were caused by L. pharomachri, a species distinct from, but closely related to, L. acicola. The discovery of L. pharomachri in Colombia is the first incidence of the pathogen causing a serious disease problem and the first occurrence on the hosts P. patula and P. maximinoi. A sexual state for L. pharomachri was discovered for the first time, and the description of the species has thus been emended.

Application of Remote Sensing Data for Assessment of Bark Beetle Attacks in Pine Plantations in Kirkovo Region, the Eastern Rhodopes

Intensive forest afforestation with native pine species was developed in the 1960s on degraded and deforested lands in the region of the Eastern Rhodopes (south-eastern Bulgaria). Severe damage by wet snow was registered in the coniferous forests of the Rhodopes in March 2015. In the following years, bark beetle attacks were registered on the broken and felled fresh wood. As a result, bark beetle infestation spots appeared in the pine plantations. In the period 2019–2021, damage caused by bark beetles was assessed in the region of State Forestry Kirkovo (the Eastern Rhodopes, south-eastern Bulgaria). An integrated approach using the data of the information system of the Executive Forest Agency (ISEFA), remote sensing data obtained by an “eBee SQ” unmanned aerial vehicle (UAV) equipped with a “Parrot Sequoia” multispectral camera, and subsequent terrestrial observations, was applied. ISEFA data showed that there was no serious damage caused by abiotic and biotic factors in the pine forests of SF Kirkovo until 2014. Snow damage in 2015 affected 513 ha of pine plantations, and bark beetle infestations reached up to 1316 ha in 2016. In 2019, a total of 226.87 ha of pine plantations were captured in three localities—Fotinovo, Kirkovo, and Kremen. The relative share of damage caused by bark beetles was greater in P. sylvestris plantations (15.3–23.0%), compared to damage in P. nigra (2.3%). Four different categories of normalised difference vegetation index (NDVI) were separated in bark beetle infestation spots—living trees, dead trees, grass and shrub vegetation, stones and rocks. The NDVI values in locations with living trees varied between 0.500 (spaces between tree crowns) and 0.700 (central part of the crown projection) (an average of 0.617). In the locations with dead trees, the average values of NDVI of lying trees was 0.273, and in standing trees, NDVI varied between 0.275 (central part of crown projections) and 0.424 (spaces between tree crowns). In the locations with grass and shrub vegetation, stones and rocks, the average NDVI was 0.436 and 0.329, respectively. In the field study, average defoliation of 31.2–32.3% was registered in P. sylvestris plantations, and 47.4% in P. nigra plantations. Defoliations mainly were caused by pine processionary moth (Thaumetopoea pityocampa) and fungal pathogens (Dothistroma septosporum and Lecanosticta acicola). The damage was caused by Ips acuminatus (in P. sylvestris only), and I. sexdentatus, Tomicus piniperda and T. minor (in P. sylvestris and P. nigra). Infestations by other xylophages, such as Phaenops cyanea, Rhagium inquisitor, and Pissodes spp., were also found on pine stems.

First report of Lecanosticta acicola causing brown spot needle blight on Atlas cedar in France

Lecanosticta acicola, the causal agent of brown spot needle blight, has been responsible for severe damage on pines in North and Central America, Asia, and since the 1990s, in Europe (van der Nest et al., 2019). In France it has been described on various pine species since 1993 (Chandelier et al., 1994; Rapet & Chauvel, 1994), mainly in south-western regions. In 2018, L. acicola was detected for the first time on a non-pine host in an arboretum in Turkey on a Lebanon cedar (Cedrus libani) showing needle blight symptoms (Oskay et al., 2020). Since 2019 it has been considered a regulated non-quarantine pest in the European Union. In spring 2020, light to severe defoliation and severe reddening of the attached needles, starting from the lower parts of the tree, were observed on twigs of adult Atlas cedar (Cedrus atlantica) planted in 1998 in a forest in the Tarn-et-Garonne department (south-west France). About 50% of the cedar trees in the plot showed these symptoms (Figure 1) but no mortality was seen. Samples were collected and analysed in December 2020. Needles with brown spots and necroses (Figures 2, 3) were incubated at room temperature in a moist chamber. After seven days incubation, black conidiomata developed. Olivaceous brown verruculose conidia were observed (Figure 4). They were cylindrical with a truncate base and a rounded apex, mainly curved and three-celled, 35–50 × 5–6 μm, similar to that reported by Oskay et al. (2020). The fungus was identified as Lecanosticta acicola based on its morphological features. Lecanosticta acicola was isolated from conidiomata on malt extract + 100 ppm chloramphenicol agar medium, total DNA was extracted from the obtained culture and the ITS region was amplified by PCR using the ITS5/ITS4 primers (Whiteet al., 1990). The amplicon was sequenced (GenBank Accession No. OM517169.1) and BLAST analysis showed 100% identity with a L. acicola reference sequence, NR_120239.1 (CBS 133791 – ITS region). In parallel, total DNA was extracted from symptomatic needle pieces and the presence of L. acicola was confirmed by a specific real-time PCR assay using the L. acicola-specific primer/probe combination Latef-F1/-R1/-P1 (Iooset al., 2010). This is the first report of Lecanosticta acicola affecting Cedrus atlantica globally and the first report of a non-pine host species in France and in the European Union. In autumn 2021, L. acicola was detected again on Atlas cedar, in a few 15- to 20-year-old forest trees showing similar symptoms in the Dordogne and Gers departments (south-west France). Pinus spp. (including Pinus nigra subsp. laricio) are widely present in the regions concerned, brown spot needle blight has not been identified despite intensive inspection of trees in this genus close to the affected cedars. Research is in progress to learn more about the origin of this outbreak and a survey has started targeting L. acicola and cedars more generally, in south-west France to provide more information on the disease. The multiple detections in different areas may suggest that it is now established on Atlas cedar, a species which is being planted in southern France in response to climate change. The susceptibility of Cedrus spp. and other conifers to brown spot needle blight and the threat that L. acicola represents on non-pine hosts in the natural environment are of major concern. The authors want to thank Y. Lacouture and J. Hubele for their sample collection, and Johann Hubele, CRPF Occitanie for providing the photograph of the symptoms in Figure 1.

The Increasing Threat to European Forests from the Invasive Foliar Pine Pathogen, Lecanosticta Acicola

The Increasing Threat to European Forests from the Invasive Foliar Pine Pathogen, Lecanosticta Acicola

Weather Variables Associated with Spore Dispersal of Lecanosticta acicola Causing Pine Needle Blight in Northern Spain.

In the last decade, the impact of needle blight fungal pathogens on the health status of forests in northern Spain has marked a turning point in forest production systems based on Pinus radiata species. Dothistroma needle blight caused by Dothistroma septosporum and D. pini, and brown spot needle blight caused by Lecanosticta acicola, coexist in these ecosystems. There is a clear dominance of L. acicola with respect to the other two pathogens and evidence of sexual reproduction in the area. Understanding L. acicola spore dispersal dynamics within climatic determinants is necessary to establish more efficient management strategies to increase the sustainability of forest ecosystems. In this study, spore counts of 15 spore traps placed in Pinus ecosystems were recorded in 2019 and spore abundance dependency on weather data was analysed using generalised additive models. During the collection period, the model that best fit the number of trapped spores included the daily maximum temperature and daily cumulative precipitation, which was associated to higher spore counts. The presence of conidia was detected from January and maximum peaks of spore dispersal were generally observed from September to November.

Dothistroma septosporum Not Detected in Pinus sylvestris Seed Trees from Investigated Stands in Southern Poland

In recent years, the decline of pine stands in Europe, including Poland, has been caused by the emerging needle pathogen Dothistroma septosporum. Although this fungus appears to preferentially infect Pinus pini, P. pinaster or P. radiata in Southern Europe, it has been reported in stands of P. nigra, P. mugo and P. sylvestris from Southern Poland. Our preliminary tests of symptomatic needles of diseased pines, including black pine (P. nigra), showed the presence of both D. septosporum and D. pini—the latter as the first report in Poland. No other endophytic pathogen, i.e., Lecanosticta acicola or Cenangium ferruginosum, were found. More extensive molecular surveying based on β-tub2 amplification of DNA in needle samples from 72 seed trees of P. sylvestris in nine different Forest Districts of Southern Poland did not find the presence of D. septosporum. Our study revealed that the seed trees from which we collected propagation material were free from the pathogen, and its endophytic behavior was not confirmed in our testing. Consequently, these investigated trees of P. sylvestris should be suitable for seed collection and propagation, following the requirements of “good” phytosanitary quality as “pathogen-free” pine seeds used for reforestation.

Host range, genetic variability, and mating types of Lecanosticta acicola in Slovakia

ABSTRACT In recent years, there has been an apparent Europe-wide emerging presence of brown spot needle blight, a disease of pine species caused by the fungus Lecanosticta acicola. In this study, we report the first well-documented occurrences of the pathogen in Slovakia, identified molecularly using species-specific primers and based on sequencing of the ITS region and TEF1 gene. Among the material collected from 84 locations within the country, L. acicola was present in 17 samples from 13 different locations, mainly distributed in urban environments. Four pine species were identified as hosts, among which, Pinus nigra and P. mugo were found to be the most frequently infected. Analysis of the mating type genes of 24 isolates obtained from two localities revealed the presence of a single mating type in Slovakia. All analyzed ITS sequences of the Slovak isolates were found to be uniform. However, although analysis of the TEF1 gene indicated that all Slovak isolates could be grouped into a single lineage, we detected nucleotide polymorphisms suggestive of a certain degree of genetic diversification within central European populations of the fungus.

Development of an acoustic method for wood disease assessment

Over the past years, the Lecanosticta acicola fungus or brown band is seriously damaging the pine forests of northern Spain. This fungus happens to dry the leaves and branches of trees. The present article describes the equipment and methodology for assessing the severity and spread of diseases in trees quickly, easily and cheaply. The concept is based on a basic assumption: a sick tree does not sound the same when it is hit as a healthy one does. The breakthrough character of the present work comes from a basic mechanical principle: if a tree loses water its density is reduced, so the sound that it makes when it is hit, also known as its acoustic response, is higher. If the tree is healthy it will grow, so the sound will be the same or deeper. The human ear cannot distinguish these variations or quantify them, but a microphone with an acquisition system can. After initial proofs of concept on real trunks, the function that relates the frequency increase to the degree of dehydration of the tree, and therefore to the severity of the disease, has been identified. Then, the method has been tested in a real forest with sick pines and compared to visual inspection of an expert. After several months of tests, it has been concluded that the trend of the acoustic method coincides with the visual assessment, with the difference that it is objective, while visual inspection is not. It has even demonstrated to be able to foresee the healing of trees before new leaves start to sprout.

Development of a Rapid Loop-Mediated Isothermal Amplification Assay for the Detection of Dothistroma septosporum

A Loop-Mediated Isothermal Amplification (LAMP) assay was developed for the detection of the pine pathogen Dothistroma septosporum (G. Dorog.) M. Morelet. The specificity of the LAMP assay was tested using a selection of pine needle fungi, including Dothistroma pini Hulbary, and Lecanosticta acicola (Thüm.) Syd.; only D. septosporum DNA was amplified by the test. In terms of sensitivity, the assay was able to detect as little as 1 pg of total D. septosporum DNA. This assay enables DNA extracted from diseased host needles to be rapidly tested for the presence of D. septosporum using relatively simple to operate equipment away from a fully equipped molecular biology laboratory.

Optimization of the micropropagation of elite adult trees of Sequoia sempervirens: forest species of interest in the Basque Country, Spain

Forest trees are renewable sources of timber and other valuable non-timber products. Nowadays, the increase in population and demand for forestry products results in overexploitation of forestry. Therefore, there is an urgent need to produce elite plants with higher productivity under stress derived from climate change to have available to afforestation. For this reason, propagation methods should be improved to be more efficient in terms of quality and productivity. The main species planted in the Basque Country is Pinus radiata; during the last three years, Pinus radiata plantations have suffered a fungus attack affecting mainly needles until the tree's death. This crisis is caused by the combined action of two fungi of the genus Dothistroma and Lecanosticta acicola, whose expansion seems to have been enhanced by weather-related factors, such as humid and hot summers. Although we have evidence of this disease's presence in our mountains since 1942, the disease has had a speedy expansion with an aggressive effect for reasons that are not scientifically known today. For the above, Basque Country forestry sector is looking for alternative species to be used in its plantations. Part of the forestry sector considers that Sequoia sempervirens could be a good choice for plantations. Besides, its high-quality wood and its tolerance to the attack of several pathogens and other diseases derived from climate change are characteristics that could confer some advantage over other forest species. The main goal of this study was to optimize the micropropagation of adult elite trees of Sequoia sempervirens. The effect of 6-benzylaminopurine, meta-Topolin and Kinetin, and 4 types of explant in the multiplication stage were analyzed to carry out this objective. Furthermore, the effect of two types of auxins: 1-naphthalene acetic acid, indole-3-butyric acid, and a mixture of both, were evaluated on the induction of roots and their subsequent effect on the acclimatization process. The best multiplication index was obtained when 4.4 µM 6-benzylaminopurine and apical explants longer than 1.5 cm of length were used. The root induction percentage was 75% in the most responsive genotype analyzed when 4.4 µM 6-benzylaminopurine was used on the induction stage, and 50 µM of 1-naphthalene acetic acid was used for rooting. Finally, after 3 months in the greenhouse, the explants cultured with Kinetin and rooted in a culture medium with indole-3-butyric acid showed the highest acclimatization success (94%).

First Report of Mycosphaerella dearnessii, Teleomorph of Lecanosticta acicola, in Europe

Conifers severely affected by brown needle blight disease caused by the ascomycete Lecanosticta acicola (Thüm.) Syd. show defoliation, reduced growth, and death. Although L. acicola has been known in Europe since 1942, its teleomorph, Mycosphaerella dearnessii Rostrup, has not yet been found. In this brief, we address the occurrence of Mycosphaerella dearnessii in dead needles cast from Pinus radiata D. Don collected in the north of Spain (Basque country). To our knowledge, this is the first report of M. dearnessii, teleomorph of L. acicola, in Europe.