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AbstractLingonberry (Vaccinium vitis-idaea L.) is a dwarf shrub that is native to Northern climates. The berries are harvested from wild plants and the disease incidence in the crop is generally low. However, disease pressure may increase since the surface area dedicated to the crop is expected to expand in the future. In 2021 and 2022, brown necrotic leaves and stem dieback symptoms were observed on lingonberry plants grown at the St. John’s Research and Development Center, Newfoundland and Labrador, Canada. Pathogens were isolated from the diseased plant tissues and identified as Neopestalotiopsis rosae (n = 2) and Neopestalotiopsis zimbabwana (n = 2) using colony and conidia morphology as well as sequencing of the Internal Transcribed Spacer (ITS), beta-tubulin gene (ß-tub), and the translation elongation factor 1-alpha gene (tef1). Pathogenicity assays in detached lingonberry and strawberry leaves as well as lingonberry plants indicated that all four isolates were able to cause disease. This is the first report of N. rosae and N. zimbabwana causing leaf spot and stem dieback of lingonberry. Further monitoring of this disease is important to understand its prevalence in berry crops, as Neopestalotiopsis spp. in Canada have been reported to occur since 2018 in strawberry and other small fruits. Control measures and strategies are required to mitigate the potential risk from the disease, as there are no registered fungicides available to the growers. [ABSTRACT FROM AUTHOR]

Salmonberry (Rubus spectabilis) and thimbleberry (Rubus nutkanus) are important native berry plants for Indigenous communities and restoration sites in the coastal region of British Columbia (BC). Compared to cultivated berry plants, information on the diseases impacting native berry plant species is limited. In late August 2022, powdery mildew symptoms and signs were observed on field plots of salmonberry and thimbleberry plants at the Agassiz Research and Development Centre, BC. The disease symptoms progressed until the end of September. The morphology of conidiophores and conidia when examined under a compound and scanning electron microscope showed they matched with those of Podosphaera aphanis. DNA from diseased foliage was subjected to PCR amplification with primers representing the internal transcribed spacer (ITS) region of rDNA followed by sequencing. The corresponding sequences from both hosts showed >99% similarity to P. aphanis in GenBank and grouped with several accessions of P. aphanis following phylogenetic analysis. In artificially inoculated trials conducted in the greenhouse, powdery mildew symptoms developed within 3−4 weeks post-inoculation and P. aphanis isolates from salmonberry and thimbleberry were cross-pathogenic to each host. To our knowledge, this is the first study characterizing the powdery mildew pathogen infecting salmonberry and thimbleberry and demonstrating cross-pathogenicity to both hosts. The outcomes from this study provide insight into the biology of the powdery mildew pathogen infecting native Rubus spp. [ABSTRACT FROM AUTHOR]

Potato and tomato are grown in all Canadian provinces and contribute billions of dollars in exports and sales. Late blight, caused by Phytophthora infestans, is a destructive disease of potato and tomato worldwide and is responsible for millions of dollars in losses annually. Changes in pathogen strains were reported to be associated with late blight epidemics in several regions and pose challenges to late blight management. In British Columbia (BC), diverse strains of P. infestans were reported. Using multiplex microsatellite or simple sequence repeat (SSR) markers, we identified the new genotype US17 of P. infestans from samples of potato and tomato with late blight in BC. All isolates were of the A1 mating type. One, five, and one isolates were sensitive, moderately resistant, and highly resistant to metalaxyl-m, respectively. This is the first report of the occurrence of the US17 genotype in BC and Canada. The US17 strain was also able to cause tuber rot and foliar blight symptoms in potato in pathogen-inoculated assays. [ABSTRACT FROM AUTHOR]

Phytophthora rubi is a primary causal agent of Phytophthora root rot and wilting of raspberry (Rubus idaeus L.)worldwide. The disease is a major concern for raspberry growers in Canada and USA. To date, no information is available on genomic diversity of P. rubi population from raspberry in Canada. Using a PCR-free library prep with dual-indexing for an Illumina HiSEQX running a 2x150 bp configuration, we generated whole genome sequence data of P. rubi isolates (n = 25) recovered during 2018 to 2020 from nine fields, four locations and four cultivars of raspberry growing areas of British Columbia, Canada. The assembled genome of 24 isolates of P. rubi averaged 8,541 scaffolds, 309× coverage, and 65,960,000 bp. We exploited single nucleotide polymorphisms (SNPs) obtained from whole genome sequence data to analyze the genome structure and genetic diversity of the P. rubi isolates. Lowheterozygosity among the 72% of pathogen isolates and standardized index of association revealed that those isolates were clonal. Principal component analysis, discriminant analysis of principal component, and phylogenetic tree revealed that P. rubi isolates clustered with the raspberry specific cultivars. This study provides novel resources and insight into genome structure, genetic diversity, and reproductive biology of P rubi isolated from red raspberry. The availability of the P. rubi genomes also provides valuable resources for future comparative genomic and evolutionary studies for oomycetes pathogens. [ABSTRACT FROM AUTHOR]

Raspberry root rot and wilting complex (RRWC), primarily caused by Phytophthora rubi, is the most important disease for raspberry producers in Canada. There is currently little to no information on phenotypic diversity or sensitivity to metalaxyl-m of P. rubi isolates affecting raspberries in Canada. This study was conducted to understand the diversity in virulence and sensitivity to metalaxyl-m of P. rubi populations collected from diverse raspberry cultivars, fields, and locations during 2018–2020. All isolates of P. rubi (n = 24) were pathogenic on 'Chemainus' raspberry and showed significant variation (P < 0.05) in days to first foliar symptom development (DFSD) and progress in wilting index, as indicated by relative areas under disease progress curves (rAUDPC). Principal component analyses identified that root rot index, rAUDPC, DFSD, and percentage reduction in root length and weight were important variables in assessing pathogen virulence. Metalaxyl-m sensitivity was assessed using a radial growth assay and effective concentrations that inhibited 50% of mycelial growth (EC50) were determined for 44 isolates. The EC50 values ranged from 0.035–4.71 µg mL−1 with a mean value of 0.793 µg mL−1. About 61% of the isolates were very sensitive (EC50 values <0.20 µg mL−1), 25% of isolates were considered sensitive (EC50 values of 0.21–1.18 µg mL−1), and 14% of isolates showed reduced sensitivity to metalaxyl-m (EC50 value range of 1.19–4.71 µg mL−1). Knowledge of pathogen phenotypic diversity will be useful for raspberry breeders in screening genotypes against RRWC and the results of the fungicide sensitivity study will be useful in developing management strategies for RRWC. [ABSTRACT FROM AUTHOR]

Phytophthora species are primary causal agents of raspberry root rot and wilting complex (RRWC), a disease complex that is of major concern to raspberry producers worldwide. Accurate identification of the causal agents is a first step for effective disease management. Advancements in molecular diagnostics can facilitate the detection of multiple pathogen species associated with this disease complex. We developed multiplex targeted-sequencing methods using degenerate primers for heat shock protein 90, elongation factor 1α and β-tubulin genes to identify Phytophthora species causing RRWC. One hundred and twenty-eight isolates recovered during 2018 to 2020 from diverse fields in major raspberry growing areas of British Columbia (BC) were sequenced and identified by comparing with known reference sequences of 142 Phytophthora species, 111 Pythium species, and nine Phytopythium species in the NCBI database. This multiplex targeted-sequencing method was highly specific and identified two species of Phytophthora associated with RRWC. These were P. rubi (85% of isolates) and P. gonapodyides (15% of isolates). Phytophthora rubi was predominantly isolated from the cultivars 'Chemainus' (51%), 'Rudi' (27%) and 'Meeker' (15%), whereas P. gonapodyides was predominately isolated from the moderately resistant cultivar 'Cascade Bounty'. Pathogenicity studies on intact plants and detached leaves confirmed that P. rubi and P. gonapodyides can cause symptoms of RRWC on raspberry, thus fulfilling Koch's postulates. To our knowledge, this is the first report of P. gonapodyides as a causal agent of RRWC on raspberry in BC. This study provides novel insights into the identification and species composition of Phytophthora associated with RRWC in raspberry production systems. [ABSTRACT FROM AUTHOR]

Red raspberry (Rubus idaeus L.) is an important fruit crop in British Columbia, Canada, and the Pacific Northwest (PNW) region of the USA, as well as in other regions of the world. Root rot and wilting complex (RRWC), primarily caused by Phytophthora rubi, is the most important biotic constraint responsible for declining raspberry production in these regions, causing millions of dollars in losses. Other root-infecting fungal species and the root lesion nematode (Pratylenchus penetrans) may also be found associated with the disease complex. The average lifespan of raspberry plantings in the PNW is 10 to 12 years, which is reduced to 5 years by the disease complex. Phytophthora spp. play a predominant role in the RRWC complex due to the persistent nature of oospores, rapid dispersal of inoculum, and the polycyclic nature of infection, all of which increase disease severity. In this review, we discuss the current understanding of Phytophthora spp. and other pathogens associated with the RRWC, including pathogen biology and the disease cycle, the impact of infection on the plant, as well as current and potential cultural, biological, and chemical options for management. In addition, we discuss breeding efforts for disease resistance, including conventional and molecular approaches to identify sources of resistance, molecular markers linked to potential resistance genes, and their incorporation into elite breeding materials or cultivars. We also present the current gaps in knowledge, unique challenges, and future perspectives in sustainable disease management of this important disease complex. [ABSTRACT FROM AUTHOR]

A trichothecene biosynthesis gene (TRI)-based PCR assay is employed to analyze a collection of 336 isolates from Gibberella zeae from barley, wheat, potatoes, and sugar beets and determine the toxigenic potential of G. zeae. The findings from the studies might be applied to monitor mycotoxin contamination and to formulate Fusarium head blight (FHB) management strategies for these crops.

Cercospora leaf spot (CLS), caused by Cercospora beticola, is the most detrimental disease of sugar beet in temperate climates. In the Great Lakes region, CLS was well managed by pyraclostrobin-based programmes using the decision support tool BEETcast™. Due to C. beticola resistance to pyraclostrobin in the region, other groups of fungicides were evaluated. Field experiments were conducted at six sites from 2013 to 2015 in Pain Court (PC) and Ridgetown (RT), Ontario. BEETcast™ application schedules for prothioconazole and mancozeb as well as carrier volume (115 and 235 L ha−1) were compared with label-based (calendar) applications. When disease intensity was high, the conservative calendar application schedule reduced the standardized area under the disease progress curve (sAUDPC) by an average of 84% compared with all BEETcast™ schedules, and the BEETcast™ 50/35 schedule (235 L ha−1) reduced sAUDPC by 48% compared with the 55/50 schedules. However, there were fewer differences among application schedules at sites with low or moderate disease intensity. BEETcast™ application schedules reduced the number of fungicide applications by 34-55%. All application schedules increased sucrose (%) and recoverable white sugar (RWS) to an equivalent level, but none of the schedules increased profit margin compared with the non-treated control. Using a carrier volume of 235 L ha−1 reduced sAUDPC by 28% compared with 115 L ha−1 at one site when disease severity exceeded 95% in non-treated control plots. Thus, management recommendations should consider that CLS severity is reduced by application schedules using a shortened interval and appropriate carrier volume, but this does not necessarily result in higher beet or sucrose yield or increases in profit margin. [ABSTRACT FROM AUTHOR]

:Cercospora beticolais the most important pathogen of sugar beet in temperate climates and is the causal agent of Cercospora leaf spot (CLS). The relationships among weather variables, disease severity and the aerial concentration ofC. beticolaconidia were assessed in 2014 and 2015. Volumetric spore traps were deployed to quantify conidia concentration every 6 h in Pain Court (PC) and Ridgetown (RT), Ontario. Mean daily air temperature (AT) and relative humidity (RH) were rarely at optimal levels for CLS development. Conidia were first detected in early May in RT both years and PC in 2015, and in mid-June in PC 2014. CLS symptoms were not observed until 75–91 days after the first detection of conidia. Thus, the presence of conidia was not a limiting factor for disease development. Daily conidia concentration peaked (0.83 spores m−3) between 12 pm and 6 pm and was lowest (0.34 spores m−3) between 12 am and 6 am at all sites, providing evidence of a diurnal effect for airborneC. beticolaconidia. A logistic curve explained the relationship between cumulative weekly conidia concentration and CLS severity (R2 ≥ 0.93, P < 0.0001), but CLS severity associated with levels of conidia accumulation was variable among sites. Mean AT 0 h before conidia capture was most influential on aerial conidia concentration compared with other weather variables (R2 = 0.11, P < 0.0001). Additional research is required to validate the relationship among mean daily AT, airborneC. beticolaconidia and CLS epidemics. Sous les climats tempérés,Cercospora beticolaest le plus important agent pathogène de la betterave à sucre et il est l’agent causal de la tache cercosporéenne (TC). En 2014 et 2015, les relations entre les variables météorologiques, la gravité de la maladie et la concentration aérienne de conidies ont été évaluées. Des pièges à spores volumétriques ont été installés pour quantifier la concentration de conidies toutes les six heures à Pain Court (PC) et Ridgetown (RT), en Ontario. La température quotidienne moyenne de l’air (TA) et l’humidité relative (HR) ont rarement atteint des niveaux optimaux promouvant le développement de la TC. Au cours des deux années, les conidies ont d’abord été détectées pour la première fois au début de mai à RT, puis à PC en 2015 et à la mi-juin à PC en 2014. Il a fallu de 75 à 91 jours avant que les symptômes de la TC soient observés, et ce, après la première détection des conidies. Ainsi, la présence des conidies n’était pas un facteur limitatif quant au développement de la maladie. La concentration quotidienne de conidies atteignait son plus haut niveau (0.83 spores m−3) de midi à 18 h et son plus bas (0.34 spores m−3), de minuit à 6 h, à tous les sites, attestant un effet diurne favorisant les conidies deC. beticolatransportées dans l’atmosphère. Une courbe logistique a expliqué la relation entre la concentration hebdomadaire cumulée de conidies et la gravité de la TC (R2≥ 0.93, P < 0.0001), mais cette dernière, associée aux taux d’accumulation de conidies, variait d’un site à l’autre. La TA moyenne à minuit précédant la capture des conidies influençait grandement la concentration de conidies transportées dans l’atmosphère, comparativement aux autres variables météorologiques (R2≥ 0.11, P < 0.0001). De plus amples recherches sont requises pour valider la relation entre la TA moyenne quotidienne, la concentration de conidies deC. beticolatransportées dans l’atmosphère et les épidémies de TC. [ABSTRACT FROM AUTHOR]

Common root rot ( CRR) and spot blotch, caused by Cochliobolus sativus (Ito and Kurib.) Drechsl. ex Dast., are important diseases of barley ( Hordeum vulgare L.) and wheat ( Triticum aestivum L.) worldwide. However, the population biology of C. sativus is still poorly understood. In this study, the genetic structure of three C. sativus populations, consisting of isolates sampled respectively from barley leaves ( BL), barley roots ( BR) and wheat roots ( WR) in North Dakota, was analysed with amplified fragment length polymorphism ( AFLP) markers. A total of 127 AFLP loci were generated among 208 C. sativus isolates analysed with three primer combinations. Gene diversity ( H = 0.277-0.335) were high in all three populations. Genetic variation among C. sativus individuals within population accounted for 74%, whereas 26% of the genetic variation was explained among populations. Genetic differentiation was high ( ØPT = 0.261, corrected [ABSTRACT FROM AUTHOR]

The article focuses on the organic agriculture project in Nepal called "Research and Support to Organic Agriculture in Tanahu District of Nepal," which was started in April 2010. The international project was a joint effort of such organizations as the Agricultural Institute of Canada (AIC), the Canadian Society of Agronomy (CSA) and the Canadian Society of Nepal. It claims that the agriculture sector accounts for 32% of Nepal's gross domestic product (GDP).

Gibberella zeae, the principal cause of Fusarium head blight (FHB) of barley, contaminates grains with several mycotoxins, which creates a serious problem for the malting barley industry in the United States, China, and Europe. However, limited studies have been conducted on the trichothecene profiles and population genetic structure of G. zeae isolates collected from barley in the United States. Trichothecene biosynthesis gene (TRI)-based polymerase chain reaction (PCR) assays and 10 variable number tandem repeat (VNTR) markers were used to determine the genetic diversity and compare the trichothecene profiles of an older population (n = 115 isolates) of G. zeae collected in 1997 to 2000 with a newer population (n = 147 isolates) collected in 2008. Samples were from across the major barley-growing regions in North Dakota and Minnesota. The results of TRI-based PCR assays were further validated using a subset of 32 and 28 isolates of G. zeae by sequence analysis and gas chromatography, respectively. TRI-based PCR assays revealed that all the G. zeae isolates in both populations had markers for deoxynivalenol (DON), and the frequencies of isolates with a 3-acetyldeoxynivalenol (3-ADON) marker in the newer population were ≈11-told higher than those among isolates in the older population. G. zeae populations from barley in the Midwest of the United States showed no spatial structure, and all the isolates were solidly in clade 7 of G. zeae, which is quite different from other barley-growing areas of world, where multiple species of G. zeae are commonly found in close proximity and display spatial structure. VNTR analysis showed high gene diversity (H = 0.82 to 0.83) and genotypic diversity but low linkage disequilibrium (LD = 0.02 to 0.07) in both populations. Low genetic differentiation (FST = 0.013) and high gene flow (Nm = 36.84) was observed between the two populations and among subpopulations within the same population (Nm = 12.77 to 29.97), suggesting that temporal and spatial variations had little influence on population differentiation in the Upper Midwest. Similarly, low FST (0.02) was observed between 3-ADON and 15-acetyldeoxynivalenol populations, indicating minor influence of the chemotype of G. zeae isolates on population subdivision, although there was a rapid increase in the frequencies of isolates with the 3-ADON marker in the Upper Midwest between the older collection made in 1997 to 2000 and the newer collection made in 2008. This study provides information to barley-breeding programs for their selection of isolates of G. zeae for evaluating barley genotypes for resistance to FHB and DON accumulation. [ABSTRACT FROM AUTHOR]

Baseline sensitivity was determined using in vitro radial growth assay for Fusarium oxysporum, Fusarium graminearum, and a novel uncharacterized Fusarium sp. nov. from sugarbeet, and F. sambucinum from potato, to metconazole, triticonazole, and thiabendazole. All the isolates from sugarbeet and a thiabendazole-sensitive F. sambucinum isolate were sensitive to the tested fungicides. A thiabendazole-resistant isolate of F. sambucinum was resistant to thiabendazole but sensitive to the other two fungicides. The EC50 values of F. oxysporum, F. graminearum, and F. sp. nov. for triticonazole were 0.51 μg ml-1, 2.15 μg ml-1, and 0.04 μg ml-1, respectively. The EC50 values of F. oxysporum, F. graminearum, and F. sp. nov. for metconazole were 0.04 μg ml-1, 0.03 μg ml-1, and 0.02 μg ml-1, respectively. The EC50 values of F. oxysporum, F. graminearum, and F. sp. nov. for thiabendazole were 0.57 μg ml-1, 0.54 μg ml-1, and 0.64 μg ml-1, respectively. Generally, a higher concentration of triticonazole and thiabendazole compared to metconazole were required to reduce colony growth by 50%. The low EC50 values of metconazole, triticonazole, and thiabendazole for the Fusarium species tested suggest that they are potential candidates for control of Fusarium diseases of sugarbeet. Research is needed to determine the effectiveness of these fungicides for control of Fusarium diseases under field conditions. [ABSTRACT FROM AUTHOR]

Fusarium graminearum causes Fusarium head blight (FHB) in small grains worldwide. Although primarily a pathogen of cereals, it also can infect noncereal crops such as potato and sugar beet in the United States. We used a real-time polymerase chain reaction (PCR) method based on intergenic sequences specific to the trichodiene synthase gene (Tri5) from F. graminearum. TaqMan probe and primers were designed and used to estimate DNA content of the pathogen (FgDNA) in the susceptible wheat cv. Grandin after inoculation with the 21 isolates of F. graminearum collected from potato, sugar beet, and wheat. The presence of nine mycotoxins was analyzed in the inoculated wheat heads by gas chromatography and mass spectrometry. All isolates contained the Tri5 gene and were virulent to cv. Grandin. Isolates of F. graminearum differed significantly in virulence (expressed as disease severity), FgDNA content, and mycotoxin accumulation. Potato isolates showed greater variability in producing different mycotoxins than sugar beet and wheat isolates. Correlation analysis showed a significant (P < 0.001) positive relationship between FgDNA content and FHB severity or deoxynivalenol (DON) production. Moreover, a significant (P < 0.001) positive correlation between FHB severity and DON content was observed. Our findings revealed that F. graminearum causing potato dry rot and sugar beet decay could be potential sources of inoculum for FHB epidemics in wheat. Real-time PCR assay provides sensitive and accurate quantification of F. graminearum in wheat and can be useful for monitoring the colonization of wheat grains by F. graminearum in controlled environments, and evaluating wheat germplasms for resistance to FHB. [ABSTRACT FROM AUTHOR]

Peppers (Capsicum sp.) are an increasingly important crop because of their use as a vegetable, spice, and food colorant. The oomycete Phytophthora capsid is one of the most devastating pathogens to pepper production worldwide, causing more than $100 million in losses annually. Developing cultivars resistant to P. capsid is challenging because of the many physiological races that exist and new races that are continuously evolving. This problem is confounded by the lack of a universal system of race characterization. As a basis to develop a global anticipatory breeding program. New Mexico recombinant inbred lines (NMRILs) functioned as a host differential for Phytophthora root rot to characterize the race structure of P. capsid populations in Taiwan. Using the NMRILs, 24 new races were identified, illustrating the utility and usefulness of the NMRILs for anticipatory breeding. Virulence of P. capsid was observed to be geographically specific and in two virulence clusters. Interestingly, all but two isolates collected in 2016 were the A2 mating type, which is a shift from the predominantly A1 mating type isolates collected prior to 2008. The NMRILs host differential provides an approach for scientists to work together on a global scale when breeding for resistance as well as on a local level for regional gene deployment. Additionally, we propose that the current race numbering system, which has no biological meaning, be supplemented with the virulence phenotype, based on the susceptible NMRILs to a given isolate. This work provides insights into the population dynamics of P. capsid and interactions within the highly complex Capsicum-Phylophthora pathosystem, and offers a basis for similar research in other crops. [ABSTRACT FROM AUTHOR]