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1.
The annual plant Impatiens glandulifera (Himalayan balsam) is the most widespread invasive non‐native weed in the British Isles. Manual control is widely used, but is costly and laborious. Recently, biological control using the rust fungus Puccinia komarovii var. glanduliferae has been trialled. We designed an experiment to assess the impact of these control methods on invertebrate communities in relation to unmanaged and uninvaded habitats, and to determine whether mycorrhizal inoculation aided post‐control recovery of these communities. Sixty invaded and twenty uninvaded field soil blocks were transplanted to the experiment site, where a mycorrhizal inoculum was added to half of all blocks. Biological and mechanical control treatments were applied to twenty invaded blocks independently; the twenty remaining invaded blocks were left intact. Above‐ and belowground invertebrate samples were collected from the blocks at the end of the growing season. Overall, aboveground invertebrate abundance increased with the removal of I. glandulifera, and several groups showed signs of recovery within one growing season. The effect of mechanical control was more variable in belowground invertebrates. Biological control did not affect aboveground invertebrate abundance but resulted in large increases in populations of belowground Collembola. Our experiment demonstrates that mechanical removal of I. glandulifera can cause rapid increases in invertebrate abundance and that its biological control with P. komarovii var. glanduliferae also has the potential to benefit native invertebrate communities.  相似文献   

2.
After a difficult start, classical biological control of weeds is becoming recognized as an option for management of invasive plants in European Union (EU) Member States with intentional releases in three countries over the past 5 years. Many European countries are benefitting from the presence of Stenopelmus rufinasus, the azolla weevil, which has been accidentally introduced to the region. However, the UK experience with the official release of the psyllid Aphalara itadori against Japanese knotweed (Fallopia japonica) and the subsequent release of the rust Puccinia komarovii var glanduliferae against Impatiens glandulifera showed the regulatory framework that could be followed by EU Member States. This process was followed in advance of the subsequent release of Trichilogaster acaciaelongifoliae, a specific Australian bud‐galling wasp, against the invasive Acacia longifolia in Portugal. Soon the case of Ophraella communa, another accidental introduction that is severely limiting Ambrosia artemisiifolia populations, will influence affected countries, some of which have been uninterested in this technique until now, to consider the advantages and disadvantages of classical biocontrol. The future looks bright for classical weed biocontrol and the EU Regulation on Invasive Species should further aid this situation.  相似文献   

3.
The rust fungus, Puccinia komarovii var. glanduliferae, has been introduced into the UK for biological control of the invasive weed, Impatiens glandulifera (Himalayan balsam). However, establishment of the pathogen has differed across the country, which may be partly explained by variation in plant genotype. The aim of this study was to examine whether there is a further layer of phenotypic resistance, provided by indigenous foliar endophytic fungi. Culturable endophytes were isolated from a number of different balsam populations, and the commonest species were inoculated into ‘clean’ balsam plants, to test their interactions with the rust. We found that endophyte communities within balsam are low in diversity and become more dissimilar with increasing distance between populations. Three endophytes (Colletotrichum acutatum, Alternaria alternata and Cladosporium oxysporum) were common and appeared to be antagonistic to the rust, reducing pustule number and mitigating the effect of the pathogen on plant biomass. I. glandulifera thus partially conforms to the endophyte-enemy release hypothesis, in that as an introduced species, it has an impoverished endophyte complement, acquired from the local environment. However, these endophytes represent a potential barrier to effective biological control and future weed control strategies need to find strains of rust that can overcome plant genetic resistance and the overlaying phenotypic resistance, conferred by endophytes. Future classical biological control programmes of weeds must therefore take into account the fungal bodyguards that invasive species may acquire in their introduced ranges.  相似文献   

4.
Himalayan balsam (Impatiens glandulifera) is one of the most invasive weeds across Europe. The rust fungus, Puccinia komarovii var. glanduliferae has been introduced as a biological control agent, but success has been patchy. Here, we investigated whether mycorrhizal and endophytic fungi can affect rust efficacy and plant growth. Over three experiments, we found that AM fungi and the rust alone or together consistently reduced plant growth, but this depended on the identity of species in the AM inoculum. Meanwhile, AM fungi increased infection frequency of the endophyte Colletotrichum acutatum. Rust inoculation had no detrimental effects on mycorrhizal colonisation or C. acutatum infection, but the latter two fungi reduced rust sporulation. However, plant size was reduced when all three fungal types were present, suggesting that a combined fungal inoculum offers a promising approach for the control of this weed.  相似文献   

5.
In 2014, the rust fungus Puccinia komarovii var. glanduliferae, native to the foothills of the Himalayas from Kashmir to Western Nepal, became the first fungal agent to be released into Europe for the classical biological control of a non-native weed. The target, Impatiens glandulifera or Himalayan balsam, is a prolific invader of riparian habitats in Europe and North America. During the period 2015–2018, a strain of the rust from India was released at a total of 36 sites, in 17 counties in England and Wales. There was limited field infection in 2015 and inoculation experiments conducted under controlled conditions revealed significant variation in the susceptibility of plant populations to the rust, with some showing immunity. Subsequently, a second strain of the rust from Pakistan was released in 2017 and was found to infect a different cohort of Himalayan balsam populations. The rust mass production methodology, and field inoculation and monitoring protocol, are detailed, and plants were tested for susceptibility to both rust strains prior to field release. Levels of foliar infection at selected sites in 2017 and 2018 are presented, as well as seedling infection rates in the spring of 2019. The results show that the rust is able to overwinter and establish populations in stands of Himalayan balsam in England. The issues involved with measuring the impact of the biological control agent are discussed.  相似文献   

6.
The rust fungus Austropuccinia psidii has spread globally and naturalized in areas with naïve species of Myrtaceae. Previous studies have revealed multiple strains of A. psidii within South America and two strains outside of its native range. The rust spreads by windborne mitotic urediniospores, which are the dominant spore stage. Teliospores and basidiospores of A. psidii are also formed; however, the biological role of these stages in the life cycle is unknown. Experiments presented here tested whether basidiospores of A. psidii could infect Syzygium jambos. The sori produced by infection with basidiospores were screened with five microsatellite markers to confirm whether they were a product of recombination. The findings showed that basidiospores of A. psidii could cause infection on species of Myrtaceae and the resulting sori were a product of recombination. This has important implications for programmes that breed for resistance to this aggressive pathogen in commercial eucalypt forestry.  相似文献   

7.
The genome size of most rust species is unknown due, in part, to technical constraints, especially the difficulty in accessing spores to extract the nuclei for cytometry. Using the urediniospores of coffee rust, Hemileia vastatrix, an improved methodology involving flow cytometry was developed for accurate measurement of the nuclear genome size. The results revealed that the genome of this primitive rust fungus is unusually large – measuring 1C‐value = 0·75 pg (733·5 Mb) – significantly bigger than other species quantified thus far in the more advanced rust lineages. The evolutionary consequences and the potential ecological constraints of this large genome size are discussed in relation to the epidemiology of coffee rust.  相似文献   

8.
A population of Impatiens glandulifera Royle, an invasive plant species native to the Western Himalayas, was recorded in 2013 near the village Gorno Sedlarce in the north‐western mountainous region of the Republic of Macedonia. I. glandulifera is a new alien species to the Macedonian flora. The surveys revealed an intensive growth and a low to medium density population of I. glandulifera. The population's density was not quantified, but several stands of different sizes were found. A rapid ecological risk assessment, mainly based on knowledge about invasion histories in North–Western and Central European countries, showed that this species, which is on the EPPO List of Invasive Alien Plants, is a serious threat to Macedonian biodiversity. Biological invasions of I. glandulifera affect biodiversity worldwide, and, consequently, the invaded ecosystems may experience significant losses in economic and cultural values. There is a clear need to develop a strategy for control of I. glandulifera to protect biodiversity, as a whole.  相似文献   

9.
The exotic rust pathogen Puccinia psidii is now widespread along the east coast of Australia from temperate Victoria to tropical far north Queensland, with a current host range exceeding 200 species from 37 myrtaceous genera. To determine the threat P. psidii poses to plantation and native eucalypts, artificial inoculation was used to screen germplasm of spotted gum (Corymbia spp.) for resistance to the biotype of P. psidii that has become established in Australia. The objective was to characterize resistance to P. psidii within the Corymbia species complex so that management strategies for the deployment of germplasm from existing breeding programmes of these spotted gum species could be developed. Symptom development initiated 7 days after inoculation, with resistant and susceptible seedlings identified within all species, provenances and families. Inter‐ and intraspecific variability in rust resistance was observed among spotted gum species. There was no apparent relationship between climatic conditions at the provenance origin and disease resistance. The heritability estimates for all assessments are moderate to high and indicate a significant level of additive genetic variance for rust resistance within the populations. The results of this study clearly identify potential to select for resistance at the family level within the tested populations. While the potential for P. psidii to detrimentally impact upon Corymbia in the nursery and in young plantations was demonstrated, estimations of the heritability of resistance suggest that efforts to enhance this trait through breeding have reasonable prospects for success.  相似文献   

10.
Puccinia psidii, the causal agent of myrtle rust, was first recorded from Latin America more than 100 years ago. It occurs on many native species of Myrtaceae in Latin America and also infects non‐native plantation‐grown Eucalyptus species in the region. The pathogen has gradually spread to new areas including Australia and most recently South Africa. The aim of this study was to consider the susceptibility of selected Eucalyptus genotypes, particularly those of interest to South African forestry, to infection by P. psidii. In addition, risk maps were compiled based on suitable climatic conditions and the occurrence of potential susceptible tree species. This made it possible to identify the season when P. psidii would be most likely to infect and to define the geographic areas where the rust disease would be most likely to establish in South Africa. As expected, variation in susceptibility was observed between eucalypt genotypes tested. Importantly, species commonly planted in South Africa show good potential for yielding disease‐tolerant material for future planting. Myrtle rust is predicted to be more common in spring and summer. Coastal areas, as well as areas in South Africa with subtropical climates, are more conducive to outbreaks of the pathogen.  相似文献   

11.
Rust fungi in the genus Melampsora usually cause disease on hosts in the Salicaceae. Identification of Melampsora species is often complicated due to few differences in spore morphology and little publicly available comparative sequence data. Weeping willow trees (primarily Salix babylonica and its hybrids) have been reported to be infected by 11 Melampsora species; however, most of these records are based on morphological characterization. New collections of rust fungi on weeping willows from the central USA were analysed using a combination of morphology, ITS and LSU rDNA sequencing, and host data to determine that they represent an undescribed rust fungus, Melampsora ferrinii sp. nov. Additional studies of herbarium material revealed that M. ferrinii has occasionally been collected but identified as M. epitea. In addition to North America, M. ferrinii is also present in South America and has been infecting weeping willows there since at least the 1990s.  相似文献   

12.
Impatiens glandulifera is a globally successful invader that primarily spreads along riparian habitats; however, during the last ~20 years, it has started to colonise forests, but little has been published on impacts of this recent spread. Several factors may have contributed to this phenomenon: (i) high propagule pressure from large and widespread riparian populations, (ii) extensive anthropogenic and natural disturbances in the forest ecosystems, (iii) increased use of forest machinery efficiently spreading the seeds together with (iv) a wide environmental tolerance of the species. The impacts of I. glandulifera on native communities in forests are manifold. Contrasting effects are reported on native plant species diversity, richness and growth of saplings of co-occurring species, as well as negative effects on soil mycorrhizal fungi. We suggest that the eradication of I. glandulifera populations in forests is more feasible than along watercourses because the recolonisation in forests is limited and, in some cases, populations are outcompeted by woody species during succession.  相似文献   

13.
Impatiens glandulifera is one of the most widespread invasive plant species in the UK. Although aspects of its biology are known, there is little information about its association with microbial communities, both above ground and below ground. Furthermore, it is unknown whether this species exhibits any form of plant–soil feedback (PSF), commonly seen in other invasive weeds. We conducted a PSF experiment, in which plants of I. glandulifera were grown in soil that supported the species and compared with plants grown in a control soil from the same locality. Soil nutrients were measured, and the soil and foliar microbial communities were assessed. Impatiens glandulifera grew larger and faster in conditioned soil compared with the control. Higher levels of phosphate were also found in conditioned soils. Arbuscular mycorrhizal fungal (AMF) colonisation was lower in conditioned soils, suggesting that I. glandulifera may rapidly alter AMF communities in invaded areas. PSFs had a significant effect on the foliar endophyte community, with clear separation of species between conditioned and control soils. These results show that I. glandulifera displayed a positive PSF and the PSF mechanism extended beyond the soil microbial community to affect foliar endophytes. The observed increase in endophytes in plants grown in conditioned soil could enhance resistance to herbivory, thus further accentuating the invasive properties of this species.  相似文献   

14.
Dothistroma needle blight (DNB), caused by Dothistroma septosporum, is the most important disease currently affecting pine plantations in Britain. Intraspecific variation in susceptibility to DNB has been observed in several pine species, but it is not clear if similar variation occurs in Pinus sylvestris (Scots pine), Britain's only native pine. In three separate experiments 2‐ and 3‐year‐old Scots pine saplings from six native Scottish populations were artificially inoculated with D. septosporum conidial suspensions and incubated under conditions optimal for disease development. Conidial suspensions were produced using a single isolate from northeast Scotland. In one experiment, plants were also treated with various spore suspension concentrations to assess the impact of inoculum load on disease severity. There were no significant interactions between host population, plant height, and experiment/inoculum load (anova , P > 0·05), but population, height and inoculum load all significantly affected disease severity (anova , P < 0·05). Among the 2‐year‐old trees, those from Amat were less susceptible than those from Glen Loyne and Glen Cannich (anova , P < 0·05). Among the 3‐year‐old trees, those from Beinn Eighe were less susceptible than those from Abernethy. Plant height and DNB susceptibility had a slightly negative relationship. The use of a spore suspension with a concentration of 1·6 × 106 spores mL?1 was optimum for disease development. In an in vitro experiment, production of conidia was greater when cultures were incubated in darkness. This paper is the first to report intraspecific variation in DNB susceptibility within Scots pine.  相似文献   

15.
Coffee leaf rust is the most limiting disease for coffee cultivation in Brazil. Despite its importance, relatively little is known about the genetic diversity of Hemileia vastatrix, the rust causal agent. In this work, the DNA from 112 monopustule isolates from different geographic locations and coffee genotypes were analysed by amplified fragment length polymorphisms (AFLP). The objectives were to assess the influence of the host and geographic origin on the diversity and population differentiation in H. vastatrix. The fungal population showed a low level of genotypic diversity. Gene diversity (h) was 0·027 and the hypothesis of random mating in the total population was rejected, but evidence for recombination was found for two subpopulations (São Paulo and Paraná). The analysis of molecular variance revealed that 90% of the genetic distribution of the pathogen occurs among isolates within the subpopulation (states or host of origin). There was no correlation between geographic and genetic distance (r = ?0·024, P = 0·74), which together with the high number of migrants and the low degree of differentiation in populations of H. vastatrix, is consistent with the fact that the inoculum is probably easily dispersed by wind over long distances, allowing dispersal of the pathogen among coffee growing areas in Brazil. Therefore, it is difficult to predict the durability of resistant sources to coffee rust. The recommendation for the breeding programmes is thus to incorporate multigenic resistance as a control strategy.  相似文献   

16.
Myrtle rust (Austropuccinia psidii) is an invasive species causing damage to Myrtaceae species in natural and managed ecosystems in many countries. To better understand myrtle rust epidemiology we studied latent period (LP) and ontogenic resistance in relation to temperature on three susceptible hosts (Metrosideros excelsa, Lophomyrtus bullata × L. obcordata and Syzygium jambos). The latent period curve was U-shaped, with latent development >0 from between 8 and 10 °C, depending on the host, to 32 °C. Optimum range was 22–28 °C with minimum LP of 5–7 days. Peak spore production occurred over about 2 weeks, starting about 1 week after the LP ended. Some spore production continued for 1–2 months. Comparison of the LP data with field temperatures indicated that the uredinial stage of A. psidii can overwinter in the latent phase in temperate areas of New Zealand and southern Australia and, therefore, uredinial or telial reinfection is not required during winter. The LP information was used to correct the LP function in a New Zealand myrtle rust climatic risk model. The transition of emergent leaf and stem tissues in susceptible Myrtaceae genotypes from susceptible to immune (ontogenic resistance) was characterized in terms of uredinium density and LP. Onset of ontogenic resistance was closely linked to the degree of leaf expansion, with fully expanded leaves being immune to infection. Because ontogenic resistance restricts infection to periods when growth flushes occur, understanding it is crucial for explaining the seasonality of myrtle rust development in the natural environment.  相似文献   

17.
Outbreaks of a rust disease in eucalypt forestry plantations and nurseries in Kenya, Mozambique and South Africa occurred between 2009 and 2014. The pathogen was identified using morphology and molecular phylogenetic analyses as an undescribed species in the Phakopsoraceae. A systematic study, based on nuclear ribosomal DNA, showed that it is a species of Phakopsora, herein named Phakopsora myrtacearum sp. nov. This new species of rust is the second validly described species on Eucalyptus, along with Puccinia psidii. Phakopsora myrtacearum is distinguished from P. psidii by leaf symptoms, morphology of the urediniospores and distinct phylogenetic placement. Phakopsora myrtacearum has been found on three species of Eucalyptus in Kenya, Mozambique and South Africa, and it may have future negative implications for commercial forestry in these areas.  相似文献   

18.
The biocontrol effect of Clonostachys rosea (strains 016 and 1457) on Fusarium graminearum, F. avenaceum, F. verticillioides, F. langsethiae, F. poae, F. sporotrichioides, F. culmorum and Microdochium nivale was evaluated on naturally infected wheat stalks exposed to field conditions for 180 days. Experiments were conducted at two locations in Argentina, Marcos Juarez and Río Cuarto. Antagonists were applied as conidial suspensions at two inoculum levels. Pathogens were quantified by TaqMan real‐time qPCR. During the first year at Marcos Juarez, biocontrol was observed in one antagonist treatment for F. graminearum after 90 days (73% reduction) but after 180 days, the pathogen decreased to undetectable levels. During the second year, biocontrol was observed in three antagonist treatments for F. graminearum and F. avenaceum (68·3% and 98·9% DNA reduction, respectively, after 90 days). Fusarium verticillioides was not controlled at Marcos Juarez. At Río Cuarto, biocontrol effects were observed in several treatments at different intervals, with a mean DNA reduction of 88·7% for F. graminearum and F. avenaceum, and 100% reduction for F. verticillioides in two treatments after 180 days. Populations of F. avenaceum and F. verticillioides were stable; meanwhile, F. graminearum population levels varied during the first 90 days, and low levels were observed after 180 days. The other pathogens were not detected. The study showed that wheat stalks were important reservoirs for F. avenaceum and F. verticillioides populations but less favourable for F. graminearum survival. Clonostachys rosea (strain 1457) showed potential to reduce the Fusarium spp. on wheat stalks.  相似文献   

19.
Sugarcane breeding programmes rank the resistance of genotypes to Puccinia kuehnii, causal agent of orange rust, according to levels of disease severity. However, during the screening stages, this method of assessment can lead to precipitous elimination of genotypes with promising agronomic traits but showing mild symptoms of rust such as flecks or lesions that do not produce spores. This study aimed to propose a new method to classify the resistance of sugarcane genotypes to orange rust by counting sporulating lesions. Five sugarcane varieties with different levels of resistance to P. kuehnii were inoculated with two pathogen populations under controlled conditions. The disease severity (SEV), total number of lesions (TNL), and total number of sporulating lesions (TNSL) were evaluated in a 20 cm leaf fragment from the most diseased leaf. The TNL and TNSL evaluations were performed at 11, 16 and 21 days after inoculation (DAI) and SEV at 21 DAI. The thresholds of 80% and 8% of sporulating lesions (SL) separated susceptible from the intermediate varieties and intermediate from the resistant ones, respectively. It is proposed that the method of counting sporulating lesions be used in screening genotypes for resistance to P. kuehnii in sugarcane breeding programmes.  相似文献   

20.
Myrtle rust poses a significant biosecurity threat to Australia with potential for long-term damaging impacts on native flora and plant industries. This study describes the disease cycle of Austropuccinia psidii, the myrtle rust pathogen, in Eucalyptus globulus and Eucalyptus obliqua, two commercially and ecologically important species from different subgenera of Eucalyptus. Ontogeny and morphology of infection structures of A. psidii on plants of both Eucalyptus species with different rust response phenotypes, i.e. completely resistant, hypersensitive and highly susceptible, were investigated. Plants were inoculated with single-uredinium-derived urediniospores and examined by scanning electron microscopy. No differences between rust response phenotypes were observed in germination of urediniospores, formation of appressoria or length of germ tubes. The growth of germ tubes had no affinity towards stomata of either species. Histological observations indicated direct penetration by infection pegs through the leaf cuticle and no penetration beyond the epidermis on rust-resistant E. obliqua. Eucalyptus obliqua plants that were identified as susceptible to A. psidii at 3- and 6-months-old showed no disease when reinoculated with A. psidii at 12-months-old; this indicated possible early acquisition of adult plant resistance to A. psidii in this species. In the susceptible phenotype of E. globulus rust inoculation led to rapid colonization of leaf parenchyma cells with the disease cycle completed within 10 days. These findings provide valuable insights into host–pathogen interactions in the Eucalyptus–A. psidii pathosystem, which might be useful for the development of effective rust control strategies across Eucalyptus subgenera.  相似文献   

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