Root infection of canker pathogens, Fusarium circinatum and Diplodia sapinea, in asymptomatic trees in Pinus radiata and Pinus pinaster plantations

[EN] The existence of a latent stage within host tissue of the pine pathogens Fusarium circinatum and Diplodia sapinea, the causal agents of pitch canker and shoot blight disease respectively, has previously been cited. However, studies on this cryptic phase in each disease lifecycle has only been focused on the host aerial parts but not on the roots. Therefore, our objective was to analyze the presence of both pathogens in roots of non-symptomatic mature trees in plantations where the pathogens are known to be causing canker symptoms. For that, we sampled roots from ten non-symptomatic and ten symptomatic trees in three Pinus radiata and one Pinus pinaster plantations in Basque Country, Spain. Both pathogens were isolated from roots of non-symptomatic trees in a higher frequency than from roots of symptomatic trees, 23.3% and 6.6% respectively for D. sapinea and 16.6% and 3.3% respectively for F. circinatum. Neither pathogens was detected in the P. pinaster plantation. The two pathogens were never isolated from the same tree. A high molecular variability was observed for D. sapinea isolates with six different haplotypes and two mating types for the eleven characterized isolates, but only one haplotype and mating type was found for F. circinatum, with all isolates of both fungi being proved pathogenic. These results evidence the importance root infection may have in the disease lifecycle and, therefore, disease management.We acknowledge Maria Teresa Morales Clemente for her excellent technical assistance. Laura Hernandez-Escribano was supported by a fellowship from INIA (FPI-INIA). Financial support for this research was provided by project RTA2013-00048-C03-01, RTA2017-00063-C04-01 and C04-03 (National Progamme I + D + I, INIA, Spain) and the Project Healthy Forest LIFE14 ENV/ES/000179. This article is-based upon work from COST Action FP1406, Pine pitch canker-strategies for management of Gibberella circinata in greenhouses and forests (PINESTRENGTH), supported by COST (European Cooperation in Science and Technology).Hernandez-Escribano, L.; Iturritxa, E.; Aragonés, A.; Mesanza, N.; Berbegal Martinez, M.; Raposo, R.; Elvira-Recuenco, M. (2018). Root infection of canker pathogens, Fusarium circinatum and Diplodia sapinea, in asymptomatic trees in Pinus radiata and Pinus pinaster plantations. Forests. 9(3):1-15. https://doi.org/10.3390/f9030128S11593Nirenberg, H. I., & O’Donnell, K. (1998). New Fusarium Species and Combinations within the Gibberella fujikuroi Species Complex. Mycologia, 90(3), 434. doi:10.2307/3761403Phillips, A. J. L., Alves, A., Abdollahzadeh, J., Slippers, B., Wingfield, M. J., Groenewald, J. Z., & Crous, P. W. (2013). The Botryosphaeriaceae: genera and species known from culture. Studies in Mycology, 76, 51-167. doi:10.3114/sim0021Wingfield, M. 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Comparison of Diplodia Tip Blight Pathogens in Spanish and North American Pine Ecosystems

[EN] Diplodia tip blight is the most ubiquitous and abundant disease in Spanish Pinus radiata plantations. The economic losses in forest stands can be very severe because of its abundance in cones and seeds together with the low genetic diversity of the host. Pinus resinosa is not genetically diverse in North America either, and Diplodia shoot blight is a common disease. Disease control may require management designs to be adapted for each region. The genetic diversity of the pathogen could be an indicator of its virulence and spreading capacity. Our objective was to understand the diversity of Diplodia spp. in Spanish plantations and to compare it with the structure of American populations to collaborate in future management guidelines. Genotypic diversity was investigated using microsatellite markers. Eight loci (SS9-SS16) were polymorphic for the 322 isolates genotyped. The results indicate that Diplodia sapinea is the most frequent Diplodia species present in plantations of the north of Spain and has high genetic diversity. The higher genetic diversity recorded in Spain in comparison to previous studies could be influenced by the intensity of the sampling and the evidence about the remarkable influence of the sample type.This research was funded by INIA, grant number: RTA 2017-00063-C04-03, LIFE programme, grant number: LIFE14 ENV/ES/000179 and by the Basque Government, grant number FUNGITRAP 19-00031. Red pine cone collection in New England and pathogen isolation was funded by USDA Forest Service.Aragonés, A.; Manzanos, T.; Stanosz, G.; Munck, IA.; Raposo, R.; Elvira-Recuenco, M.; Berbegal Martinez, M.... (2021). Comparison of Diplodia Tip Blight Pathogens in Spanish and North American Pine Ecosystems. Microorganisms. 9(12):1-17. https://doi.org/10.3390/microorganisms9122565S11791

Pine Pitch Canker and Insects: Regional Risks, Environmental Regulation, and Practical Management Options

Producción CientíficaPine pitch canker (PPC), caused by the pathogenic fungus Fusarium circinatum (Nirenberg and O’ Donnell), is a serious threat to pine forests globally. The recent introduction of the pathogen to Southern Europe and its spread in Mediterranean region is alarming considering the immense ecological and economic importance of pines in the region. Pines in forests and nurseries can be infected, resulting in severe growth losses and mortality. The pathogen is known to spread in plants for planting and in seeds, and results from recent studies have indicated that F. circinatum may also spread through phoretic associations with certain insects. With this review, we aim to expand the current understanding of the risk of insect-mediated spread of PPC in different parts of Europe. Through the joint action of a multinational researcher team, we collate the existing information about the insect species spectrum in different biogeographic conditions and scrutinize the potential of these insects to transmit F. circinatum spores in forests and nurseries. We also discuss the impact of environmental factors and forest management in this context. We present evidence for the existence of a high diversity of insects with potential to weaken pines and disseminate PPC in Europe, including several common beetle species. In many parts of Europe, temperatures are projected to rise, which may promote the activity of several insect species, supporting multivoltinism and thus, further amplifying the risk of insect-mediated dissemination of PPC. Integrated pest management (IPM) solutions that comply with forest management practices need to be developed to reduce this risk. We recommend careful monitoring of insect populations as the basis for successful IPM. Improved understanding of environmental control of the interaction between insects, the pathogen, and host trees is needed in order to support development of bio-rational strategies to safeguard European pine trees and forests against F. circinatum in future.European Cooperation in Science and Technology (COST Action FP1406 PINESTRENGTH)Ministerio de Economía, Industria y Competitividad - Fondo Europeo de Desarrollo Regional (project AGL2015-69370-R)Portuguese Foundation for Science and Technology (contract IF/00471/2013/CP1203/CT0001)Russian Foundation for Basic Research (grant 17-04-01486)Saint Petersburg State Polytechnical University (project 2019-0420

In vitro evaluation of wood preservatives to prevent dispersal of pitch canker pathogen, Fusarium circinatum

Fusarium circinatum, the causal agent of pitch canker disease on pines, can be disseminated by wood produced in infested areas. The purpose of the study was to evaluate the effect of wood preservatives, commonly used against sapstain and wood-decay fungi, on growth and sporulation of Fusarium circinatum. Seven active ingredients of antisapstain and anti-wood-decay preservatives were evaluated by their inhibition of mycelial growth. Propiconazole, tebuconazole, and 3-iodo-2-propinyl butyl carbamate (IPBC) were effective against F. circinatum, whereas hydroxycarbonate of cooper was not. An assay was also conducted to evaluate the efficacy of three commercial antisapstain and two anti-wood-decay preservatives on Pinus radiata sapwood blocks that were previously inoculated with Fusarium circinatum. The product with the best efficacy was an antidecay preservative composed of tebuconazole, propiconazole, and dichlofluanid. None of the antisapstain preservatives tested was effective even though they contained fungicidal ingredients. Effects of dosage, product application, and formulation on the efficacy of these preservatives are discussed. © 2015 Blackwell Verlag GmbH

Biocontrol of Fusarium circinatum Infection of Young Pinus radiata Trees

Pitch canker, caused by the fungus Fusarium circinatum, is a major disease of Pinus radiata currently controlled to some extent in nurseries by good hygiene and application of synthetic fungicides. The aim of this study was to evaluate alternative strategies to control fungal infections in nurseries and young pine plantations. The antagonistic effects of biocontrol bacteria and essential oils against F. circinatum in vitro and in young P. radiata trees were assessed. Pseudomonas fluorescens, Erwinia billingiae, and Bacillus simplex reduced the growth of the fungus in vitro by 17%–29%, and decreased the density of the mycelial mat. In young P. radiata trees, the length of F. circinatum lesions was reduced by 22%–25% by the same bacterial strains. Direct application of cinnamon and/or clove essential oils to wounds in stems of two-year-old P. radiata trees also limited the damage caused by F. circinatum. Lesion length was reduced by 51% following treatment with cinnamon oil (10% v/v), and by 45% following treatment with clove oil (15% v/v) or a combination of both oils. However, the oils were toxic to younger trees. The biocontrol bacteria and essential oils show promise as prophylactic treatments to reduce the devastating effects of F. circinatum on P. radiata

Evaluation of genetic resistance in Pinus to pitch canker in Spain

Pitch canker is a disease that affects pines in many countries throughout the world. Fusarium circinatum, the causal agent of pitch canker, has recently been reported in Europe, where it is regulated as a quarantine pest. This pathogen represents a substantial threat to natural Pinus forests and plantations. To date, two mating types of F. circinatum have been described, both of which are present in Spain. To assess the potential risk of F. circinatum to Pinus in Spain, the main conifer species grown in Spain, namely Pinus sylvestris , P. nigra, P. pinaster, P. radiata , P. halepensis P. pinea and P. uncinata , were examined for their susceptibility to four Spanish isolates of F. circinatum. Two-year-old shoots were wounded and then inoculated with the four Spanish isolates, and lesion lengths were measured 2 weeks after inoculation. Pinus radiata was found to be the most susceptible species to the Spanish isolates, whereas P. pinea, P. halepensis, P. nigra, P. uncinata and P. pinaster were found to be relatively resistant and showed a significantly different lesion size from P. radiata. For P. pinaster, variations in resistance were found between provenances. One particular provenance (Meseta Castellana) was found to be more resistant than the three other provenances tested. No differences in virulence between the Mat-1 and Mat-2 isolates were detected. Overall, the low susceptibility of all native species to pitch canker suggests a moderate potential risk to the Spanish natural forests and a high potential risk to the exotic forestry of P. radiata. © Australasian Plant Pathology Society Inc. 2012

Influence of temperature and moisture duration on pathogenic life-history traits of predominant haplotypes of Fusarium circinatum on Pinus spp. in Spain

[EN] Pathogen life history traits influence epidemic development and pathogen adaptive ability to interact with their hosts in different environments. Reduced traits variation may compromise pathogen evolutionary potential, which is particularly important for introduced pathogens. Fusarium circinatum (cause of pine pitch canker) is an invasive fungal pathogen in Europe, with current distribution restricted to forest stands of Pinus radiata and Pinus pinaster in northern Spain and Portugal. This study aimed to quantify pathogenic traits of Spanish isolates of F. circinatum, with two of the strains representing the two dominant haplotypes in the Spanish population. Disease severity was measured on P. radiata, analyzing the influence of temperature and moisture duration on infection as well as the influence of temperature on spore germination, sporulation, and mycelial growth. Results indicated that the isolate representing the most common haplotype caused more severe disease on P. radiata at 25 and 30 degrees C compared with the second most common haplotype but caused less severe disease at 15 degrees C. Spore germination was higher for the most common haplotype, which produced more spores at 20 and 25 degrees C. The isolate showed hyphal melanization at 5 degrees C, which has been associated with survival and may be important because no resting structures have been described for F. circinatum. Our study determined that longer moisture periods during infection result in more severe disease from 7 to 24 h, regardless of the isolate virulence. This is the first study on virulence of the most abundant haplotypes of F. circinatum in Spain as affected by temperatures and moistureThis research was supported by Ministerio de Economia y Competitividad (Subprograma de Proyectos de I+D orientado a los Recursos y Tecnologias Agrarias en coordinacion con las Comunidades Autonomas) projects RTA 201300048-C03-01 and RTA 2017-00063-C04-01.Elvira-Recuenco, M.; Pando, V.; Berbegal Martinez, M.; Manzano Muñoz, A.; Iturritxa, E.; Raposo, R. (2021). Influence of temperature and moisture duration on pathogenic life-history traits of predominant haplotypes of Fusarium circinatum on Pinus spp. in Spain. Phytopathology. 111(11):2002-2009. https://doi.org/10.1094/PHYTO-10-20-0445-RS200220091111

Adaptive Potential of Maritime Pine (<i>Pinus pinaster</i>) Populations to the Emerging Pitch Canker Pathogen, <i>Fusarium circinatum</i>

<div><p>There is a concern on how emerging pests and diseases will affect the distribution range and adaptability of their host species, especially due to different conditions derived from climate change and growing globalization. <i>Fusarium circinatum,</i> which causes pitch canker disease in <i>Pinus</i> species, is an exotic pathogen of recent introduction in Spain that threatens its maritime pine (<i>P. pinaster</i>) stands. To predict the impact this disease will have on the species, we examine host resistance traits and their genetic architecture. Resistance phenotyping was done in a clonal provenance/progeny trial, using three-year-old cuttings artificially inoculated with the pathogen and maintained under controlled environmental conditions. A total number of 670 ramets were assessed, distributed in 10 populations, with a total of 47 families, 2 to 5 half-sibs per family, and 3–7 ramets per clone. High genetic variation was found at the three hierarchical levels studied: population, family and clone, being both additive and non-additive effects important. Narrow-sense and broad-sense heritability estimates were relatively high, with respective values of 0.43–0.58 and 0.51–0.8, depending on the resistance traits measured (lesion length, lesion length rate, time to wilting, and survival). These values suggest the species' high capacity of evolutionary response to the <i>F. circinatum</i> pathogen. A population originated in Northern Spain was the most resistant, while another from Morocco was the most susceptible. The total number of plants that did not show lesion development or presented a small lesion (length<30 mm) was 224 out of 670, indicating a high proportion of resistant trees in the offspring within the analyzed populations. We found large differences among populations and considerable genetic variation within populations, which should allow, through natural or artificial selection, the successful adaptation of maritime pine to pitch canker disease.</p></div

Survival function for the event of wilting by populations of <i>P. pinaster</i> plants inoculated with <i>F. circinatum</i> at time 0 and estimated by the Kaplan-Meier method (2013 trial).

<p>Survival function for the event of wilting by populations of <i>P. pinaster</i> plants inoculated with <i>F. circinatum</i> at time 0 and estimated by the Kaplan-Meier method (2013 trial).</p