Forest Pathology最新文献

In 2019, 18-year-old Pinus taeda trees with symptoms of chlorosis in the aerial part, shortening of needles and reduced plant growth, ultimately leading to tree decline, were found in plantations in southern Brazil. When collecting roots, a reduction in the volume of fine roots in trees and absence of ectomycorrhiza was observed. An oomycete was isolated from the roots and soil of the rhizosphere, and its pathogenicity was confirmed through Koch's postulates. The morphological characteristics of this oomycete were similar to the Phytophthora macrochlamydospora, which was confirmed by the molecular characterization from three gene regions (ITS-rDNA, COX I and TEF1α). This is the first report of P. macrochlamydospora associated with tree decline in P. taeda in Brazil and worldwide.

The recent emergence of the fungus Cryptostroma corticale in Seattle, Washington, USA is concerning because of its invasive status in Europe, where it causes sooty bark disease of maples (SBD), killing both forest and urban trees. Additionally, the fruiting bodies (stromata) of C. corticale produce allergenic spores that can impact human health. Therefore, its presence in Washington has the potential to impact the state's populace and trees, including the native bigleaf maple, Acer macrophyllum. To better determine the distribution of C. corticale in western Washington, A. macrophyllum was surveyed on 50 Washington State Park properties. Bark samples were collected from trees with fruiting bodies resembling those of C. corticale and cores were removed from mature asymptomatic trees. The presence of C. corticale was confirmed using nested PCR. Acer macrophyllum with fruiting bodies of C. corticale were well distributed throughout western Washington, with an 89% detection rate at surveyed Park properties containing A. macrophyllum. Core samples indicated that latent infections appeared well distributed and common throughout western Washington on mature A. macrophyllum, with a 91% detection rate at surveyed Park properties containing A. macrophyllum and a 68% detection rate on cored trees. Signs of SBD and evidence of latent infections of C. corticale were widespread at surveyed properties. However, signs of SBD were rare on individual trees and the overall condition of A. macrophyllum was considered vigorous at the majority of Park properties. Awareness of C. corticale, SBD, and their likelihood to be present on a property containing A. macrophyllum in western Washington should help inform management actions and demonstrate the need for future research.

The forest pathogen, Heterobasidion irregulare, is a serious threat to conifers in North America including Minnesota. Fungi native to Minnesota were isolated and tested in laboratory and field assays to evaluate their antagonism towards H. irregulare. One management strategy for plant pathogens, and especially H. irregulare, is to use fungi as biological control agents. A successful biological control agent used to manage root rot disease caused by H. irregulare is the fungus Phlebiopsis gigantea. The goal of this research was to screen different native fungi, including P. gigantea, against H. irregulare and examine and quantify their interactions in vitro and ex vitro. A set of four different antagonism assays were conducted. These assays served as a screening process involving both the laboratory and the field. Interactions were first examined with dual inoculation studies on media and wood discs of red pine (Pinus resinosa). These assays demonstrated strong inhibition and limited growth of H. irregulare by select fungi, including Phanerochaete livescens and P. gigantea. Another assay involved using soil microcosms and wood wedges of red pine. This allowed for a different examination, as wood wedges were inoculated with a candidate antagonistic fungus and placed in soil microcosms with H. irregulare. The opposite interaction was also examined with wedges inoculated with H. irregulare and then placed in soil microcosms containing different candidate fungi. In the field, large wood discs were placed around stumps and inoculated with candidate fungi in a red pine plantation infected with H. irregulare. Certain fungi performed well in different assays, but across all assays, P. gigantea performed the best. The antagonism of P. gigantea was most noticeable on wood discs and wood wedges used in vitro, as H. irregulare was not able to be reisolated from these substrates. Overall, these results provide more information on the fungi that appear to be acting as antagonists in forests to prevent H. irregulare from colonizing and provide new information on potential candidate fungi that could be used as a new biological control agent.

Seawater salt deposition was investigated in the needles of Pinus thunbergii trees growing in the coastal area of Pohang, Korea. Both green asymptomatic and brown necrotized needles were air-dried and processed for field-emission scanning electron microscopy and X-ray microanalysis. Seawater salt crystals appeared randomly deposited on the asymptomatic needles. No distinct epicuticular waxes were found in the stomata or on the needle surface. The salt crystals, which varied in size, were observed in the stomatal chambers as well as on the apertures of the Florin rings, and similar crystals were also observed on the necrotized brown needles. Sodium (Na) and chloride (Cl) were prevalent on the needles and mostly co-localized in the crystals. Magnesium was partially co-localized with Cl, but often co-occurred with potassium. Depending on the elemental composition of salts, two types of salt deposition were observed on the needles: (i) the coffee-ring pattern and (ii) the uniform pattern. The apparent NaCl crystal depositions in the stomatal chambers indicated the stomatal penetration by seawater and solutes in the seawater-sprayed needles of P. thunbergii. These results provide insights into the initial phase of seawater salt-induced injury occurring through the stomatal pathway in pine species distributed in coastal areas.

In 2021, a seedling rot disease was observed on Hinoki cypress (Chamaecyparis obtusa) seedlings in a bareroot forest nursery in Naju-si, Jeollanam-do Province, South Korea. Infected seedlings were yellowing at the disease outset but became black after severe infection. At onset of disease, seedlings began yellowing. As disease progressed, black rot of the leaves and roots was common and eventually wilt and seedling death was observed. Seedling mortality was about 30%. The causal organism was isolated from the seedlings on potato dextrose agar media. A total of nine isolates were recovered and two representative isolates were identified as Fusarium asiaticum based on morphological characterization and phylogenetic analysis of the internal transcribed spacer (ITS) region, translation elongation factor (EF1–α) and RNA polymerase II (RPB2) genes. Pathogenicity and fungicide sensitivity were tested to confirm pathogen viability and control efficacy of the disease. The fungal isolate caused severe disease in the inoculated Hinoki cypress seedlings. Also, the isolates were sensitive to benomyl, hexaconazole and pyraclostrobin and showed reduced sensitivity to penthiopyrad. In planta assays showed 98.81 and 100% disease control by the application of pyraclostrobin and hexaconazole, respectively. The pathogen was re-isolated from the inoculated seedlings and its identity was confirmed by morphological analysis fulfilling Koch's postulates. The pathogen-causing disease in the Hinoki cypress is the first reported in the host worldwide.

The present study aimed to investigate the feasibility of using a diet low in lysine content as a means for increasing the intramuscular fat (IMF) content and pork muscle quality of finishing pigs. Thirty-two crossbred gilts and barrows weighing approximately 80 kg were fed either a low-lysine diet (0.60%; Low-lys) or a control diet (0.80% lysine; Med-lys) under a 2 × 2 factorial arrangement of treatments. The animals were slaughtered at a 132-kg body weight (BW) on average, followed by physicochemical analyses and sensory evaluation on Longissimus lumborum (LL) and Semitendinosus (ST) muscles. The average daily gain (ADG) did not differ between the Med-lys and Low-lys groups. However, ADG exhibited a tendency of sex × diet interaction (p = 0.09), being greater for barrows vs. gilts on the Low-lys diet (p < 0.05), but not on the Med-lys diet. Backfat thickness adjusted for 132-kg BW also exhibited the interaction; it was greater for the Low-lys vs. Med-lys group within gilts but tended to be less for the former in barrows (p = 0.08). The IMF content was not influenced by the diet or sex in either LL or ST. The a*, b*, and Warner-Bratzler Shear Force values and fatty acid composition were influenced by the sex or diet in either or both of the muscles, but the treatment effects did not apparently influence the meat quality. Sensory scores for the flavor, juiciness, tenderness, umami, and palatability of cooked muscle were not influenced by the diet in either LL or ST. When the LL and ST data were pooled, scores for those sensory attributes were positively correlated with the IMF content, which was associated with overall greater IMF contents and greater sensory scores for ST vs. LL. Collectively, the Low-lysine diet seemingly elicited the intended lysine deficiency in gilts as indicated by the increased BFT due to the diet. However, the Low-lys diet was not effective for increasing the IMF deposition or eating quality of the pork muscle of finishing pigs slaughtered at high BW probably because its lysine content was not low enough to elicit either outcome.

Dothistroma needle blight (DNB) caused by Dothistroma septosporum is one of the most important needle diseases of Pinus spp., especially in Southern Hemisphere plantations. In Colombia, the pathogen has caused severe outbreaks in plantations of Pinus tecunumanii of the low elevation population (LE). Currently, management strategies suffer from a lack of knowledge regarding the epidemiology of D. septosporum under tropical climatic conditions. In this study we determined the patterns of conidial dispersal and considered how climatic conditions in Colombia influence them. The study was conducted over 15 consecutive months between October 2010 and December 2011 using glass slide-based spore traps. Conidia were found on the traps throughout the year, with the peak abundance during November to January (2010) and November to December (2011). During peak conidial production, relative humidity and temperature had the greatest influence on conidial dispersal. Favourable weather conditions in Colombia, particularly rainfall, have contributed to continuous conidial production throughout the year, leading to D. septosporum infections all year round. This high reproductive rate as a consequence of high precipitation is in contrast to other Southern Hemisphere and Northern Hemisphere countries with more specific periods of rainfall and infection.

The forest disease, Scots pine blister rust, is caused by the rust fungus Cronartium pini. This pathogen was previously known as the host-alternating type C. flaccidum and non-host-alternating type Peridermium pini. Recent epidemics of this disease in Northern European forests, especially young Scots pine forests in Sweden, caused significant economic and ecological losses. Cronartium pini can be identified based on the typical orange blister-like aecia in Scots pine in summer, but any molecular identification and quantification method has not been available for Cronartium spp. This study developed qPCR primers that are specific to Cronartium spp. and evaluated DNA extraction protocols from pine bark and wood to enable robust qPCR assays. As little as three Cronartium ITS copies can be detected with the protocol. Since only C. pini is known to infect Scots pine in Northern Europe, the protocols were applied to detect C. pini from Scots pine samples without typical symptoms and investigate the C. pini colonization in Scots pine branches from the forest. These results will aid the detection and quantification of C. pini in asymptomatic or symptomatic samples and monitoring Scots pine blister rust in the forest in northern Europe.

In addition to breeding for genetic resistance, lower branch pruning is a management strategy to mitigate adverse effects of Cronartium ribicola on young western white pine (Pinus monticola; WWP) in portions of the Interior Northwest, USA (INW). However, only data on heights of white pine blister rust (WPBR) cankers and post-treatment effects from outside the Oregon East Cascades (OEC) have previously informed INW pruning guidelines. To evaluate the appropriateness of these guidelines for WWP in the OEC, heights to cankers on young WWP (<30 years old) were measured in 120 plots within 12 stands throughout the OEC. Canker heights were analysed for live WWP ≥2.54 cm in diameter at 1.37 m. Incidence and severity of WPBR on live WWP, in addition to heights to cankers, varied among stands. Increased severity of WPBR (number of cankers on live-infected trees and percent mortality by WPBR) was observed in stands with the alternate host Ribes more frequently occurring in plots. Of all cankers, approximately 97% were found in the lower half of the total tree height, and only 10% of cankers on young WWP were found above the first third of the total tree height. When evaluating canker heights in all stands, mean heights to branch and bole cankers were <2.2 m. Bole cankers were lower than branch cankers (p = .01), reaffirming that potentially lethal cankers in the INW often originate from infections lower in the crown. In stands, the number of plots with Ribes present was positively correlated with the number of cankers on live-infected WWP and percent mortality of WWP due to WPBR (p < .04). As the incidence of WPBR on live WWP increased in stands, heights to the highest cankers also increased (p = .002). The number of cankers on live-infected trees was positively correlated with the mean and highest heights to cankers (p < .002). Given that the vast majority of cankers were prunable and occurred in the lower crown of young WWP, pruning lower branches to increase survival of WWP is a management option in the OEC, and prioritization of stands for treatment is recommended.

Scots pine (Pinus sylvestris) and Stone pine (Pinus pinea) are two important species used in re-forestation that are subject to damage by damping-off fungi in forest nurseries. Twenty-two isolates of Fusarium oxysporum and F. verticillioides from diseased seedlings of eight different hosts were tested for aggressiveness on seeds and seedlings of both pine species, including the effects on seedling emergence and mortality. Scots pine was more susceptible to damping-off than Stone pine, as indicated both by reduced seedling emergence and elevated seedling mortality. The impact of F. oxysporum and F. verticillioides on seeds and seedlings did not differ significantly for either pine species. Our findings support previous studies that found that these are damping-off pathogens on the studied pines. Whereas most isolates proved to be pathogenic, some isolates of both Fusarium species showed to be non-pathogenic.