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.
Summary
Lecanosticta acicola causes brown spot needle blight (BSNB) of Pinus species. The pathogen occurs mostly in the Northern Hemisphere but has also been reported in Central America and Colombia. ...BSNB can lead to stunted growth and tree mortality, and has resulted in severe damage to pine plantations in the past. There have been increasingly frequent new reports of this pathogen in Europe and in North America during the course of the past 10 years. This is despite the fact that quarantine practices and eradication protocols are in place to prevent its spread.
Taxonomy
Kingdom Fungi; Phylum Ascomycota; Subphylum Pezizomycotina; Class Dothideomycetes; Subclass Dothideomycetidae; Order Capniodales; Family Mycosphaerellaceae; Genus Lecanosticta.
Host range and distribution
Lecanosticta spp. occur on various Pinus species and are found in North America, Central America, South America (Colombia), Europe as well as Asia.
Disease symptoms
Small yellow irregular spots appear on the infected pine needles that become brown over time. They can be surrounded by a yellow halo. These characteristic brown spots develop to form narrow brown bands that result in needle death from the tips down to the point of infection. Needles are prematurely shed, leaving bare branches with tufts of new needles at the branch tips. Infection is usually most severe in the lower parts of the trees and progresses upwards into the canopies.
Useful websites
The EPPO global database providing information on L. acicola (https://gd.eppo.int/taxon/SCIRAC)
Reference genome of L. acicola available on GenBank (https://www.ncbi.nlm.nih.gov/genome/?term=Lecanosticta+acicola)
JGI Gold Genome database information sheet of L. acicola sequenced genome (https://gold.jgi.doe.gov/organism?xml:id=Go0047147)
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.
The pine needle pathogen Lecanosticta acicola has been introduced into Europe on several separate occasions with human activity supporting the pathogen's onwards spread from already established European populations into new areas.
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 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). 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.
The defoliation of the eastern white pine (Pinus strobus) across the northeastern United States is an escalating concern threatening the ecological health of northern forests and economic vitality of ...the region's lumber industry. First documented in the spring of 2010 affecting 24 328 hectares in the state of Maine, white pine needle damage (WPND) has continued to spread and is now well established in all New England states. While causal agents of WPND are known, current research is lacking in both sampling distribution and the specific environmental factor(s) that affect the development and spread of this disease complex. This study aims to construct a more detailed distribution map of the four primary causal agents within the region, as well as utilize long‐term WPND monitoring plots and data collected from land‐based weather stations to develop a climatic model to predict the severity of defoliation events in the proceeding year. Sampling results showed a greater distribution of WPND than previously reported. WPND was generally found in forest stands that compromised >50% eastern white pine by basal area. No single species, nor a specific combination of species had a dominating presence in particular states or regions, thus supporting the disease complex theory that WPND is neither caused by an individual species nor by a specific combination of species. In addition, regional weather data confirmed the trend of increasing temperature and precipitation observed in this region with the previous year's May, June, and July rainfall being the best predictor of defoliation events in the following year. Climatic models were developed to aid land managers in predicting disease severity and accordingly adjust their management decisions. Our results clearly demonstrate the role changing climate patterns have on the health of eastern white pine in the northeastern United States.
Brown 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.
Three genetically different L. acicula populations were identified. High gene flow from the eastern Lithuanian to the northern Polish population suggested that the latter may have been introduced from the central part of Lithuania.
•Pine tree’s health monitoring through their acoustic response.•Evaluation of Lecanostica acicola fungus as a result of the drying of the tree.•Correlation between frequency drift and mass ...loss.•Comparison between expert’s visual assessment and acoustic response on real trees.•Acoustic response foresees the evolution of the illness before leaves turn brown.
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.
Brown spot needle blight (BSNB), a disease of pine trees caused by the fungus Lecanosticta acicola, has been known in Slovenia since 2008 and in Croatia since 1975. Recent outbreaks in Slovenia ...prompted this study to compare L. acicola populations in these two neighbouring European countries. Sixty‐nine isolates collected from three pine species (Pinus mugo, P. halepensis and P. nigra) were used to determine the phylogenetic relationships, genetic structure, and reproductive strategy of the pathogen. EF1‐α sequences showed that Slovenian and Croatian isolates share a common ancestry with individuals from central and northern Europe. Population structure analysis revealed four distinct population clusters of L. acicola in these two countries, generally corresponding to their respective geographic location and host. An unequal ratio of mating types and a low overall genetic diversity in the population indicated a strong influence of asexual reproduction. Although some of the oldest recorded European occurrences of BSNB are from Croatia, this study provided no evidence that the population studied in Croatia was the source of the sampled outbreaks in Slovenia. Recent outbreaks of L. acicola in Slovenia are most likely due to introductions from other, yet to be identified, sources.
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.
First molecular detection of Lecanosticta acicola from Poland on Pinus mugo Raitelaitytė, Kristina; Markovskaja, Svetlana; Paulauskas, Algimantas ...
Forest pathology = Journal de pathologie forestière = Zeitschrift für Forstpathologie,
April 2020, 2020-04-00, 20200401, Volume:
50, Issue:
2
Journal Article
Peer reviewed
The presence of quarantine pathogen Lecanosticta acicola, the causal agent of brown spot needle blight, was confirmed using molecular methods for the first time in northern part of Poland on the ...coastal area adjacent to the Baltic Sea. This area includes sandy beaches, where Pinus mugo and P. sylvestris were planted. Symptomatic needles were collected in 2017 from 20 P. mugo trees growing in one stand in Ustka. Typical symptoms of brown spot needle blight infection, including dead needle tips and central zones with yellow or reddish brown, circular spots in green tissue, were observed on all samples. Only, the asexual stage of L. acicola was obtained during this work. The pathogen species identity was confirmed using classical morphological methods (microscopic examination of the infected needles), real‐time and species‐specific priming (SSPP) PCR, and ITS sequencing. Analysis of mating‐type (MAT) genes showed the presence of both mating types in northern Poland.
PDF
