Figure 5 - uploaded by James J. Worrall
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Discoloration of current-year needles at site 13. Some older needles are gray with fruiting of L. montivaga.
Source publication
An epidemic of needle cast, causing discoloration and defoliation of lodgepole pine, was observed on the Gunnison, White River, and San Isabel National Forests on both sides of the Continental Divide in the southern and central mountains of Colorado. In this general area, most stands were apparently unaffected, but the disease was locally severe. E...
Context in source publication
Context 1
... lodgepole appeared generally healthy north of Pitkin, but approaching Cumberland Pass from the south, one stand had a somewhat orange hue (site 13). Several trees near the road had current-year foliage almost all discolored, indicating very heavy infection this year ( Figure 5). 2010 needles were already gone or discolored/dead with some fruiting. ...
Citations
... During the in situ analysis, it was found that the most common symptom was the death of the distal parts of this year's needles just a few weeks after their development, while the green basal parts were unscathed. This type of symptom on the needles of various pine species can be caused by fungi of the genus Elytroderma, Lophodermella, Lophophacidium and Ploioderma [14,[30][31][32][33]. In Poland, their occurrence on the needles of P. mugo has so far not been recorded [34][35][36]. ...
... Other authors [32] observed the transverse black bands at the edge of the fruiting areas on P. contorta infected by L. montivaga. Such symptoms have also been reported now, but sporadically. ...
Pinus mugo plays a significant ecological role in the natural environment at high altitudes in the mountains including the Alps, Pyrenees, Carpathians, and Balkans. In such severe conditions, it is subjected to the harmful effects of various abiotic and biotic factors. In one of the areas of its natural occurrence in Tatra Mts. (southern Poland), for the last few years, a significant intensification of needle disease has been observed. Symptoms similar to those recorded in Tatra Mts. also occur on other Pinus species in Europe and North America, where they are caused by fungi belonging to the genus Elytroderma, Lophodermella, Lophophacidium or Ploioderma (Rhytismataceae). The current paper presents the results of research which was mainly aimed at characterization of disease symptoms observed for the first time in Poland on P. mugo needles, and identification of the main causal agent with use of the morphological and molecular technique. Based on the analyses performed at different times of the year (2015–2020), it was found that dieback symptoms initially appeared only on first-year needles, a few weeks after their development. Symptoms occur on one or both needles in the bundle. The distal parts of the needles died, while the basal parts remained green. In the following year, mainly in June and July, on the previous year’s needles attached to the shoots, mature ascomata can be seen. The fungus Lophodermella sulcigena has been identified as the cause of these symptoms. So far, the related species L. conjuncta has not been found. The morphological features of the pathogen microstructure produced on P. mugo needles are presented. Attention was drawn to certain features that may make its identification difficult, especially in terms of shapes and sizes of ascospores. The phylogenetic position of the identified causal agent in relation to closely related other species was determined. The current results confirmed that L. sulcigena shows great phylogenetic similarity to L. montivaga, which is found in North America. Nine rDNA barcode sequences of L. sulcigena obtained in this work will enrich the NCBI GenBank database. The obtained results, indicating the presence of other fungi in L. sulcigena ascomata, which may limit the spread of its ascospores, were also discussed.
... Disease symptoms on infected hosts include needle discoloration and defoliation which could negatively impact growth when severe [20]. Recently, two epidemics caused by these two pathogens were recorded in Colorado, USA [21]. Though found on the same host and in the same sites in Colorado, their ecological interaction on an individual host has not been well-documented. ...
... Though found on the same host and in the same sites in Colorado, their ecological interaction on an individual host has not been well-documented. It has been reported that, among the infected sites, all but one had only a single pathogen occurrence based on hysterothecia development, which may be due to unknown ecological differences between the two species [21] or ecological competition prevailed by the most dominant and/or aggressive pathogen [22]. Additionally, little information is known about the interaction between these pathogens and other fungal endophytes in P. contorta. ...
... Nonetheless, it has been shown that environmental factors could favor further growth and/or activity of latent pathogens. The enhanced sporulation and infection of Lophodermella pathogens with warm moisture [21] could exacerbate pathogen invasion resulting in an increase in relative abundance. This pathogen excess in host tissue then leads to an intensi ed disease incidence or severity [64, 109] and demonstrates an imbalance in an otherwise balanced system of antagonism between disease players that leads to disease development [110]. ...
Profiling the host-mycobiota interactions in healthy vs. diseased forest ecosystems helps understand the dynamics of understudied yet increasingly important threats to forest health that are emerging due to climate change. We analyzed the structural and functional changes of the mycobiota and the responses of Pinus contorta in the Lophodermella needle cast pathosystem through metabarcoding and metatranscriptomics. When needles transitioned from asymptomatic to symptomatic, dysbiosis of the mycobiota occurred, but with an enrichment of Lophodermella pathogens. Many pathogenicity-related genes were highly expressed by the mycobiota at the necrotrophic phase, suggesting an active pathogen response that are absent in asymptomatic needles. This study also revealed that Lophodermella spp. are members of a healthy needle mycobiota that have a latent lifestyles suggesting that other pine needle pathogens may have similar biology. Interestingly, P. contorta upregulated defense genes in healthy needles, indicating response to fungal recognition, while a variety of biotic and abiotic stresses genes were activated in diseased needles. Further investigation to elucidate the possible antagonistic interplay of other biotic members leading to disease progression and/or suppression is warranted. This study provides insights into microbial interactions in non-model pathosystems and contributes to the development of new forest management strategies against emerging latent pathogens.
Morphological similarities and fastidious development of increasingly emerging fungal needle pathogens impede accurate disease diagnosis and early detection. This study analyzed the specificity and sensitivity of polymerase chain reaction (PCR)-based markers developed for emerging needle cast pathogens Lophodermella concolor and L. montivaga co-occurring on Pinus contorta var. latifolia, and Bifusella linearis and L. arcuata on P. flexilis. To design primers, we utilized sequences of the internal transcribed spacer (ITS) region and single-copy gene (RH_2175) of the TCP-1/cpn60 chaperonin family searched through genomes of related species. In addition to the DNA of target and non-target fungal species that were used for primer assays, environmental samples with next generation sequencing data were used to evaluate primer sensitivity. Direct amplification using ITS primer pairs generated 248–260 bp amplicons and successfully differentiated the needle pathogens used in this study. Nested amplification of single-copy gene RH_2175 primer pairs which produced 409–527 bp amplicons detected Rhytismataceae species and discriminated both Lophodermella pathogens on P. contorta var. latifolia, respectively. While ITS-based primers had higher sensitivity than the 2175-based primers, both primer sets for L. concolor and L. montivaga detected their respective pathogens in asymptomatic and symptomatic needles. These molecular tools can help monitor and assess needle diseases for forest management and phytosanitary regimes.
Profiling the host–mycobiota interactions in healthy vs. diseased forest ecosystems helps understand the dynamics of understudied yet increasingly important threats to forest health that are emerging due to climate change. We analyzed the structural and functional changes of the mycobiota and the responses of Pinus contorta in the Lophodermella needle cast pathosystem through metabarcoding and metatranscriptomics. When needles transitioned from asymptomatic to symptomatic, dysbiosis of the mycobiota occurred, but with an enrichment of Lophodermella pathogens. Many pathogenicity-related genes were highly expressed by the mycobiota at the necrotrophic phase, showing an active pathogen response that are absent in asymptomatic needles. This study also revealed that Lophodermella spp. are members of a healthy needle mycobiota that have latent lifestyles suggesting that other pine needle pathogens may have similar biology. Interestingly, Pinus contorta upregulated defense genes in healthy needles, indicating response to fungal recognition, while a variety of biotic and abiotic stresses genes were activated in diseased needles. Further investigation to elucidate the possible antagonistic interplay of other biotic members leading to disease progression and/or suppression is warranted. This study provides insights into microbial interactions in non-model pathosystems and contributes to the development of new forest management strategies against emerging latent pathogens.
