Peronospora Sparsa Research Articles

Development of a Disease Risk Prediction Model for Downy Mildew (Peronospora sparsa) in Boysenberry

Downy mildew caused by Peronospora sparsa has resulted in serious production losses in boysenberry (Rubus hybrid), blackberry (Rubus fruticosus), and rose (Rosa sp.) in New Zealand, Mexico, and the United States and the United Kingdom, respectively. Development of a model to predict downy mildew risk would facilitate development and implementation of a disease warning system for efficient fungicide spray application in the crops affected by this disease. Because detailed disease observation data were not available, a two-step approach was applied to develop an empirical risk prediction model for P. sparsa. To identify the weather patterns associated with a high incidence of downy mildew berry infections (dryberry disease) and derive parameters for the empirical model, classification and regression tree (CART) analysis was performed. Then, fuzzy sets were applied to develop a simple model to predict the disease risk based on the parameters derived from the CART analysis. High-risk seasons with a boysenberry downy mildew incidence >10% coincided with months when the number of hours per day with temperature of 15 to 20°C averaged >9.8 over the month and the number of days with rainfall in the month was >38.7%. The Fuzzy Peronospora Sparsa (FPS) model, developed using fuzzy sets, defined relationships among high-risk events, temperature, and rainfall conditions. In a validation study, the FPS model provided correct identification of both seasons with high downy mildew risk for boysenberry, blackberry, and rose and low risk in seasons when no disease was observed. As a result, the FPS model had a significant degree of agreement between predicted and observed risks of downy mildew for those crops (P = 0.002).

Temperature effect on rose downy mildew development under environmental controlled conditions

The rose downy mildew disease, caused by Peronospora sparsa Berkeley, is one of the most important that affect rose crops in Colombia. To manage this disease, flower growers must deal with high-costs due to the excessive application of fungicides, but without good results. Studies on P. sparsa behavior have shown its narrow relationship with environmental conditions. In this study, the temperature effect was evaluated during the infection and sporulation of P. sparsa in Charlotte leaflets, a susceptible commercial variety, through an environmental controlled conditions system. Infection and sporulation were observed at different temperatures in a range of from 4 to 40°C. Infection with the absence of or very low sporulation was observed at 4°C. The most favorable pathogen responses were between 15 and 18°C in terms of inoculum concentration and sporulation percentage. There was no infection or leaflet change above 35°C. According to the results, sporulation can occur from 4 to 33°C, confirming the fact that P. sparsa is able to reproduce throughout a wide temperature range.

Evaluation of methods for long term storage of the boysenberry downy mildew pathogen <i>Peronospora sparsa</i>

Downy mildew of boysenberry is caused by the biotrophic pathogen Peronospora sparsa To ensure supplies of viable spore inoculum for infection experiments six storage methods were assessed the leaf discs cut from sporulating areas of the leaf stored dry or in 20 glycerol and spores were suspended in 20 glycerol all three of which were stored at either 20C or 80C After 1 2 4 or 6 months storage spore viability and the capability to infect leaf discs were evaluated Storage methods had no significant effects on spore germination or infection Storage time and temperature significantly (P

Fungicide spray programs to manage downy mildew (dryberry) of blackberry caused by Peronospora sparsa

Downy mildew (dryberry) of blackberry, caused by Peronospora sparsa, is a major disease of blackberry in Michoacán, México. The objective of this research was to evaluate different fungicide spray programs to manage systemic infections of downy mildew and dryberry disease in two different regions of Michoacan, Mexico in the 2007 and 2008 growing seasons. The presence of asymptomatic infections of P. sparsa in experimental plots was confirmed by nested PCR using published primers amplifying a fragment of 477 bp of the ITS region of ribosomal DNA. In 2007, the experiment was conducted in an 8-year-old commercial planting in Tangancicuaro. Fungicide applications began early in the growing season approximately 10 days after bud brake (July 10). In 2008, the experiment was conducted at the same location, but treatments began later (August 4) approximately 21 days after bud break at which time plants had fully expanded leaves. An additional plot was established in Atapan in 2008. Seven fungicide programs using commercial formulations and recommended rates of mefenoxam, potassium phosphite, azoxystrobin, captan, mancozeb, copper sulfate, Bacillus subtilis, and a sanitizing agent were tested at both locations. Results from both years and locations indicated that all programs beginning with potassium phosphite (3–4 applications) on a 10–14 day schedule after bud brake, significantly reduced the severity and incidence of downy mildew on leaves, and dryberry on fruits compared to the untreated control, regardless of the fungicide (either biological or chemical) that was applied later in the season. Programs that included 1 or 2 applications of mefenoxam, the first application in drench, early in the season also provided good control. Fungicide programs that were initiated with protectant fungicides or used protectant materials only did not provide a satisfactory level of control. Early detection of systemic infections of P. sparsa through the use of PCR and the use of fungicide spray programs based on early season applications of systemic fungicides such as potassium phosphite and mefenoxam provided good to excellent control of foliar downy mildew and dryberry of blackberry in Michoacán, México.

Evaluation of methods for sterilising boysenberry leaves for downy mildew infection studies

Downy mildew of boysenberry caused by Peronospora sparsa is a major disease problem for New Zealand growers Investigation of the biology and epidemiology of this biotrophic pathogen requires the production of sporangiospore inocula Four leaf sterilisation treatments (70 ethanol 10 bleach sterile water control) were assessed for their ability to reduce surface contaminants After treatment the leaf surfaces (six replicates) were pressed onto potato dextrose and nutrient agar plates and these were incubated at 20C for 1 week All treatments significantly (P

Evaluating electrolysed oxidising water as a fungicide using two rose varieties (Rosa sp) in greenhouse conditions

The aim of evaluating electrolysed oxidising water (EOW) for controlling botrytis (Botrytis cinerea), powdery mildew (Sphaerotheca pannosa) and downy mildew (Peronospora sparsa) using two greenhouse rose varieties was to verify this new technology’s effectiveness by contrast with traditional chemical handling. Two concentrations of hypochlorous acid in EOW were produced during electrolysis in a P1200 cell and applied at three application volumes using stationary hydraulic pressure equipment. The commercial rose varieties (Rosa sp) used here were the Orlando and Versilia varieties. The EOW used was slightly acidic type C, pH 5.0, having high-oxide-reduction potential (ORP) +850 millivolts (mV). Two types of EOW were evaluated for this study: EOW C-50 (50 ppm HOCl) and EOW C-75 (75 ppm HOCl). The test results showed the feasibility of EOW as a fungicide at the volumes tested here, providing significant control of powdery mildew which has high incidence due to climatic conditions. The best disease control was achieved by applying the highest volume; however, some curled leaflets appeared with this application.

First Report of Peronospora sparsa Causing Downy Mildew (Dryberry) of Rubus fruticosus in Mexico.

Michoacan State is the largest producer of blackberries (Rubus fruticosus) in Mexico with more than 4,000 ha in production. During the rainy season of 2007 (July to September), purple, angular, vein-delimited leaf spots along the midrib and major veins were observed. Affected young fruit lost their shine, became shriveled, and later dried. Some fruit split. Symptomatic leaflets from cv. Tupy were collected from the field in Tangancicuaro and Los Reyes counties. In the laboratory, 20 detached leaflets were washed with 10% bleach for 2 min, rinsed with sterile distilled water, and placed into sterile petri dishes containing 0.5% water agar. To promote sporulation of fungi, leaflets were incubated at 17°C with a 12-h photoperiod in a growth chamber. Sporangia and sporangiophores, which developed 20 days later on the underside of the leaves, were transferred to the underside of detached healthy leaves of the same cultivar with a sterile needle, and incubated as previously described. A set of noninoculated leaves were included as controls. Sporangiophores and sporangia developed on the underside of angular purple lesions on leaves 15 to 22 days after inoculation. Symptoms were identical to those observed on leaves in the field. The pathogenicity test was repeated twice with the same results. Sporangia were light brown, ovoid to elliptical, and measured 14 to 22 × 11 to 18 μm. Sporangiophores were dichotomously branched with slender curved ends. Symptoms on the leaves and fruit and oomycete morphology were similar to those described for downy mildew (2). To confirm pathogen identity, a product of ~500 bp of the nuclear ITS-rRNA was amplified from total DNA from symptomatic and asymptomatic leaves and fruit by nested PCR. The primers sets PS3/PS1 and PR3/PR4 were used for the first and second reaction, respectively (1,3). PCR products were sequenced in both directions and sequences were deposited in GenBank under Accession Nos. EU601168, EU601169, EU601170, and EU601171. Consensus sequences obtained in this study were compared with the same region of Peronospora sparsa (GenBank Accession Nos. EU391654 from Denmark and AF266783 from the UK). Similarity among these sequences varied between 99 and 100%. To our knowledge, this is the first report of downy mildew (dryberry) of blackberry caused by P. sparsa in Mexico.

Simple sequence repeat markers useful for sorghum downy mildew (Peronosclerospora sorghi) and related species

BackgroundA recent outbreak of sorghum downy mildew in Texas has led to the discovery of both metalaxyl resistance and a new pathotype in the causal organism, Peronosclerospora sorghi. These observations and the difficulty in resolving among phylogenetically related downy mildew pathogens dramatically point out the need for simply scored markers in order to differentiate among isolates and species, and to study the population structure within these obligate oomycetes. Here we present the initial results from the use of a biotin capture method to discover, clone and develop PCR primers that permit the use of simple sequence repeats (microsatellites) to detect differences at the DNA level.ResultsAmong the 55 primers pairs designed from clones from pathotype 3 of P. sorghi, 36 flanked microsatellite loci containing simple repeats, including 28 (55%) with dinucleotide repeats and 6 (11%) with trinucleotide repeats. A total of 22 microsatellites with CA/AC or GT/TG repeats were the most abundant (40%) and GA/AG or CT/TC types contribute 15% in our collection. When used to amplify DNA from 19 isolates from P. sorghi, as well as from 5 related species that cause downy mildew on other hosts, the number of different bands detected for each SSR primer pair using a LI-COR- DNA Analyzer ranged from two to eight. Successful cross-amplification for 12 primer pairs studied in detail using DNA from downy mildews that attack maize (P. maydis & P. philippinensis), sugar cane (P. sacchari), pearl millet (Sclerospora graminicola) and rose (Peronospora sparsa) indicate that the flanking regions are conserved in all these species. A total of 15 SSR amplicons unique to P. philippinensis (one of the potential threats to US maize production) were detected, and these have potential for development of diagnostic tests. A total of 260 alleles were obtained using 54 microsatellites primer combinations, with an average of 4.8 polymorphic markers per SSR across 34 Peronosclerospora, Peronospora and Sclerospora spp isolates studied. Cluster analysis by UPGMA as well as principal coordinate analysis (PCA) grouped the 34 isolates into three distinct groups (all 19 isolates of Peronosclerospora sorghi in cluster I, five isolates of P. maydis and three isolates of P. sacchari in cluster II and five isolates of Sclerospora graminicola in cluster III).ConclusionTo our knowledge, this is the first attempt to extensively develop SSR markers from Peronosclerospora genomic DNA. The newly developed SSR markers can be readily used to distinguish isolates within several species of the oomycetes that cause downy mildew diseases. Also, microsatellite fragments likely include retrotransposon regions of DNA and these sequences can serve as useful genetic markers for strain identification, due to their degree of variability and their widespread occurrence among sorghum, maize, sugarcane, pearl millet and rose downy mildew isolates.

Benzothiadiazole affects the leaf proteome in arctic bramble (Rubus arcticus).

Benzothiadiazole (BTH) induces resistance to the downy mildew pathogen, Peronospora sparsa, in arctic bramble, but the basis for the BTH-induced resistance is unknown. Arctic bramble cv. Mespi was treated with BTH to study the changes in leaf proteome and to identify proteins with a putative role in disease resistance. First, BTH induced strong expression of one PR-1 protein isoform, which was also induced by salicylic acid (SA). The PR-1 was responsive to BTH and exogenous SA despite a high endogenous SA content (20-25 microg/g fresh weight), which increased to an even higher level after treatment with BTH. Secondly, a total of 792 protein spots were detected in two-dimensional gel electrophoresis, eight proteins being detected solely in the BTH-treated plants. BTH caused up- or down-regulation of 72 and 31 proteins, respectively, of which 18 were tentatively identified by mass spectrometry. The up-regulation of flavanone-3-hydroxylase, alanine aminotransferase, 1-aminocyclopropane-1-carboxylate oxidase, PR-1 and PR-10 proteins may partly explain the BTH-induced resistance against P. sparsa. Other proteins with changes in intensity appear to be involved in, for example, energy metabolism and protein processing. The decline in ATP synthase, triosephosphate isomerase, fructose bisphosphate aldolase and glutamine synthetase suggests that BTH causes significant changes in primary metabolism, which provides one possible explanation for the decreased vegetative growth of foliage and rhizome observed in BTH-treated plants.

Impact of Agrochemicals on Peronospora sparsa and Phenolic Profiles in Three Rubus arcticus Cultivars

The main arctic bramble ( Rubus arcticus) cultivars are susceptible to downy mildew ( Peronospora sparsa), which seriously threatens the cultivation. The efficiency of Aliette, Euparen M, phosphite-containing Phosfik, Phostrol, Farm-Fos-44, and Kaliumfosfiet, as well as Bion was evaluated in the greenhouse. Fewer symptoms and less Peronospora DNA were found in plants treated with Euparen M and Bion, whereas Aliette, Phosfik, and Phostrol gave moderate protection. Three arctic bramble cultivars showed varying susceptibility to P. sparsa. An inexpensive and fast in vitro plate test gave results parallel with those obtained in the greenhouse. Quantitative differences were found in the phenolic profiles of the leaves of different cultivars and in different treatments. Several phenolic compounds were tentatively identified in arctic bramble for the first time, for example, monomeric and oligomeric ellagitannins and galloylglucoses. Negative correlation was found between the amount of P. sparsa DNA and flavonol glycosides and some ellagitannins in the leaves 8 days after inoculation, suggesting a possible role for these phenolics in the defense.

The use of a PCR diagnostic test to predict and control <i>Peronospora sparsa</i> downy mildew of boysenberry

The use of a PCR diagnostic test to predict and control <i>Peronospora sparsa</i> downy mildew of boysenberry

Quantification of downy mildew (Peronospora sparsa) in Rubus species using real-time PCR

Downy mildew disease caused by Peronospora sparsa, also known as ‘dryberry’ disease, is a serious threat to the cultivation of arctic bramble (Rubus arcticus) and boysenberry (Rubus spp. hybrid). A quantitative and sensitive screening method is necessary for the breeding of downy mildew resistant cultivars and for determining efficient disease control methods. A quantitative real-time PCR method using SYBR® Green I fluorescent dye was developed for the analysis of P. sparsa in arctic bramble, other Rubus species and roses. Primers were designed to amplify a P. sparsa specific 94-bp fragment from the internal transcribed spacer region (ITS1) and a 140-bp fragment from a conserved region of plant 5.8S ribosomal DNA, which served as an internal control in the samples. Linear amplification from genomic DNA and control plasmids was achieved with both primers, and even 37 fg of P. sparsa conidial DNA was detected. In the samples collected from the field, quantities as low as 0.2 ppm of P. sparsa DNA in plant DNA were detected, thus enabling the diagnosis of weak and latent infections. Arctic bramble cvs Pima, Mespi and Mesma, all showing distinct foliar symptoms, were tested to assess the relative amount of downy mildew DNA present. The symptoms and the amount of P. sparsa DNA detected correlated only in cv. Pima, indicating that visual inspection of symptoms is not a reliable method for assessing the extent of tissue infection. The number of conidiophores of P. sparsa on in vitro inoculated leaves of two arctic bramble cultivars correlated with the results obtained by real-time PCR.

The Association of Aster Yellows Phytoplasma with Rose Dieback Disease in Poland

AbstractPolymerase chain reaction (PCR) assay, restriction fragment length polymorphism analysis, sequencing of PCR‐amplified cDNA, graft transmission and mycological tests were used to investigate the possible association of phytoplasma infection with rose dieback symptoms and to identify any associated pathogen. Rose plants with shoot dieback symptoms, symptomless rose plants, and experimentally infected periwinkle seedlings were shown to be infected with phytoplasma, which was classified to the aster yellows (AY) group, subgroup 16SrI‐B, based on the analysis of the nucleotide sequence of a 1101‐bp fragment of 16S rRNA gene (GenBank accession no. AF450325). No evidence was obtained for the infection of rose plants with Verticillium albo‐atrum. The rose plants cultivated under plastic cover without heating or under outdoor conditions, in contrast to greenhouse‐grown roses, developed downy mildew symptoms caused by Peronospora sparsa.

Environmental Factors Affecting Rose Downy Mildew and Development of a Forecasting Model for a Nursery Production System.

The effect of various environmental parameters on rose downy mildew caused by Peronospora sparsa was determined under controlled conditions and in the field. In growth chambers, optimal temperatures for infection and colonization of rose leaves were 15 to 20°C and 20 to 25°C, respectively. At optimal temperatures, infection required only 2 h of leaf wetness, although disease severity increased significantly with an increasing duration of leaf wetness up to 10 h. Infection of leaves occurred at temperatures as low as 5°C with 8 h of leaf wetness. The latent period of infection varied from 4 to 7 days. Weather and disease incidence data collected from natural field epidemics were used in the development of a predictive model of rose downy mildew. Logistic regression was used to identify those weather variables that explained the largest portion of the variation in disease incidence. The optimum regression model incorporated three weather variables calculated as cumulative totals over the previous 10 days: (i) hours of leaf wetness when temperatures were less than 20°C (positive correlation); (ii) hours between 15 and 20°C (negative correlation); and (iii) hours when temperatures exceeded 30°C (negative correlation). The simplest model, which was also a good fit, included only the 10-day cumulative number of hours of leaf wetness. The critical number of hours of leaf wetness for disease development was an average of 8.4 h per day over 10 days.

Fungi Occurring on Aerial Constituents of Cultivated Blackberry ( Rubus fruticosus L.) in Norway

Cultivated blackberry (Rubus fruticosus) was recently introduced in Norway, and most plantings were established in the 1990's. Many of these plantings died back or had severe damage on leaves and stems. Plant pathogens incombination with frost injury were suspected to be the cause of the damage. In 1998-99, field and greenhouse plantings of blackberry were surveyed for the occurrence of plant pathogenic and saprophytic fungi. A total of 33 different fungi were identified in 18 cultivars from 23 plantings (19 field and 4 greenhouse). Of these, 12 were pathogenic fungi, while 21 were non-pathogenic, secondary invaders. The most important pathogens on the canes were (common name in parenthesis) Septocyta ruborum (Purple blotch), Gnomonia rubi (Gnomonia canker) and Sydowiella depressula (Sydowiella canker). Pathogenic fungi of less importance on the canes were Elsinoe veneta (Anthracnose) and Coniothyrium fuckelii (Cane blight). Peronospora sparsa (Downy mildew) was the most important fungus attacking leaves. On fruits Botrytis cinerea (Grey mould) was the most prevalent pathogen. Cladosporium spp. (Cladosporium rot) and Penicillium spp. (Blue mould) were frequently observed on fruits, but did not seem to be of significant importance. Other minor fruit rots were due to Colletotrichum gloeosporioides (Bitter rot) and Mucor sp. (Mucor rot). Phragmidium violaceum (Blackberry rust) was found on canes and leaves, but was of minor importance. G. rubi and S. depressula caused damage mostly in the thornless cultivars, and P. sparsa was found almost exclusively in the thornless cultivar 'Loch Ness'. Both thorny and thornless cultivars were damaged by S. ruborum. In greenhouses the major fungal problem was B. cinerea.

Chitosan in the control of rose powdery mildew and downy mildew

Microcrystalline chitosan at concentrations from 0.025% to 0.2% was evaluated in the control of Sphaerotheca pannosa var. rosae and Peronospora sparsa. Shrubs were sprayed with chitosan 4 times at weekly intervals. Depending on the concentration used, chitosan reduced development of powdery mildew from 43.5% to 77% and its effectiveness was similar to triforine at concentration 0.03% (standard). Observations of rose leaves under light microscopic, which had been done 24 h after spraying showed, that chitosan caused strong hyphae deformation which almost completely collapse. Cell walls of the pathogen were sunken, corrugated and longitudinally cracked. When applied against P. sparsa effectiveness of the compound at concentration 0.0625% was similar like oxadixil at dose 0.016% (standard) and ranged from 55% to 74%. Efficacy of chitosan decreased with increasing of its concentration.

First Record of Leaf Spots on Prunus laurocerasus in Belgium Caused by Phytophthora cactorum and Peronospora sparsa.

In fall 2000 and 2001, large leaf spots were observed on Prunus laurocerasus. Two different plant pathogens proved to be the cause. Based on morphological characteristics they were identified as Peronospora sparsa (downy mildew) and Phytophthora cactorum. The P. cactorum isolate (CBS 110121) was identified at the Centraalbureau voor Schimmelcultures (Utrecht, the Netherlands). Sporangia were papillate, ovoid, and deciduous, with a short pedicel. The isolate was homothallic. Chlamydospores were present and approximately 40 μm in diameter. Oogonia were 25 to 31 μm in diameter, and the antheridia were paragynous. Peronospora sparsa had been reported to infect Prunus laurocerasus in the United Kingdom (1). In Belgium, cv. Etna was very susceptible, but cvs. Rotundifolia and Marbled White were also infected. Rotundifolia was susceptible to P. cactorum. At first inspection, the two pathogens caused similar leaf symptoms: large, irregular, brown, necrotic spots on the tips, margins, and center of leaves. However, the undersides of leaves infected with Peronospora sparsa were covered with typical gray mycelium, which was absent on leaves infected with P. cactorum. P. cactorum caused concentric circles in the brown spots. Leaf spots caused by P. cactorum developed quickly in a moist chamber. Spots caused by Peronospora sparsa did not enlarge significantly on detached leaves, but in the field it caused serious losses within a few days. To prove the pathogenicity of P. cactorum, Koch's postulates were satisified on five Prunus laurocerasus Etna plants. The fungus was grown on corn meal agar for 1 week until sporangia formed. An agar plug was placed on five wounded leaves per plant and sealed with Parafilm. Inoculated plants were kept under a plastic cover for 1 day at 22°C, then the cover was removed, and the plants were kept at 20°C. Symptom development was visible after 3 days, and P. cactorum was successfully reisolated. This is the first record of P. cactorum and Peronospora sparsa leaf infection on Prunus laurocerasus in Belgium. Reference: (1) G. Hall et al. Plant Pathol. 41:224, 1992.

The effect of fungicides, irrigation and plant density on the development of Peronospora sparsa, the cause of downy mildew in rose and blackberry

SummaryDowny mildew of rose (Rosa spp.) and blackberry (Rubus fructicosus), caused by Peronospora sparsa, can cause significant losses in production. In a series of experiments, fungicides with different modes of action to the commonly used phenylamide‐based products were examined for efficacy on both crops. Cymoxanil + mancozeb + oxadixyl and fluazinam gave good downy mildew control on both rose and blackberry. On outdoor, container‐grown rose, high volume sprays of fosetyl‐aluminium were also effective, but on young micropropagated blackberry plants, application as a drench treatment was better than as a spray. Good control was also achieved on blackberry with chlorothalonil and with metalaxyl in formulation with either thiram or mancozeb. There was no evidence of loss of control with phenylamide fungicides due to resistance. Irrigation regimes were also examined on blackberry and sub‐irrigation of plants in propagation on a sand bed led to significantly lower disease levels than those found where plants had been irrigated by overhead sprinklers. Reducing the density of container‐grown rose plants had a measurable effect on the progress of downy mildew, though this was small and temporary when compared with the effect of fungicide treatment. Fungicide programmes which gave season‐long control of rose downy mildew resulted in significantly improved extension growth.

British Columbia Regional Meeting, 2001, The Canadian Phytopathological Society / Réunion régionale de la Colombie-Britannique, 2001, La Société Canadienne de Phytopathologie

British Columbia Regional Meeting, 2001, The Canadian Phytopathological Society / Réunion régionale de la Colombie-Britannique, 2001, La Société Canadienne de Phytopathologie

Variability of Peronospora Sparsa (syn. P. rubi) in Finland as Measured by Amplified Fragment Length Polymorphism

Downy mildew caused by Peronospora sparsa (syn. P. rubi) is a serious threat to commercial cultivation of arctic bramble (Rubus arcticus subsp. arcticus) in Finland. P. sparsa is distributed throughout the country in cultivated and wild arctic bramble and in cloudberry (R. chamaemorus). A total of 36 isolates of P. sparsa collected from these hosts was analysed for amplified fragment length polymorphism (AFLP). Of the 226 markers scored, 223 were polymorphic and all isolates of P. sparsa had unique AFLP fingerprints, which indicated high levels of genetic variability. An UPGMA clustering analysis of the isolates did not reveal any genetically distinguishable strains. The isolates were grouped neither according to the geographic origin nor the host from which they were isolated. Isolates of P. sparsa obtained from wild arctic bramble and one from cloudberry readily infected the leaves of the cultivated arctic bramble (cultivar ‘Pima’). Also, P. sparsa isolated from cultivated arctic bramble infected the leaves of wild arctic bramble. These data suggest that P. sparsa may be disseminated from wild arctic bramble and cloudberry to cultivated arctic bramble in the field.