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Late blight caused by Phytophthora infestans is an economically important disease of potato and tomato worldwide. In Canada, an increase in late blight incidence and severity coincided with changes in genetic composition of P. infestans. We monitored late blight incidence on tomato and potato in Pacific western and eastern Canada between 2019 and 2022, identified genotypes of P. infestans, and examined their population genetic diversity. We identified four major existing genotypes US11, US17, US8, and US23 as well as 25 new genotypes. The US11 genotype was dominant in Pacific western Canada, accounting for 59% of the total population. We discovered the US17 genotype for the first time in Canada. We revealed a higher incidence of late blight and quite diverse genotypes of P. infestans in Pacific western Canada than in eastern Canada. We found high genetic diversity of P. infestans population from Pacific western Canada, as evidenced by the high number of multilocus genotypes, high values of genetic diversity indices, and emergence of 25 new genotypes. Considering the number of disease incidence, the detection of diverse known genotypes, the emergence of novel genotypes, and the high number of isolates resistant to metalaxyl-m (95%) from Pacific western Canada, the region could play a role in establishing sexual recombination and diverse populations, which could ultimately pose challenges for late blight management. Therefore, continuous monitoring of P. infestans populations in Pacific western region and across Canada is warranted. Key points: • Genotypes of P. infestans in Pacific western were quite diverse than in eastern Canada. • We discovered US17 genotype for the first time in Canada and identified 26 novel genotypes. • Approximately 95% of P. infestans isolates were resistant to metalaxyl-m. [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 root rot and wilt (PRRW), caused by Phytophthora rubi and potentially other species of Phytophthora , is a destructive disease of raspberry in Canada and worldwide. In this study, trials were conducted over multiple years (2019–2022) in two fields, with pathogen (P. rubi) inoculated (PI) and naturally infested (NI) fields, to evaluate foliar and soil applied fungicides with different modes of action and application timings to manage PRRW. In addition, PRRW progress was also monitored in one PI field and four NI fields. In PI field plots, PPRW foliage and wilting symptoms appeared 6–8 weeks later and disease index was significantly (p < 0.0042) lower in the cultivar 'Cascade Bounty' than the cultivars 'Meeker' and 'Tulameen', indicating that 'Cascade Bounty' showed field tolerance to the disease. The efficacy of foliar fungicides (fosetyl-Al and phosphites) and soil-applied fungicides (oxathiapiprolin, metalaxyl-m, and cyazofamid) were assessed on susceptible cultivars at both sites. In PI plots, the fungicide treatments significantly enhanced (p = 0.01 to < 0.0001) numbers of primocanes and floricanes, as well as weight, percent witling index, and fruit yield of floricanes. Soil application of a tank mix or rotation of oxathiapiprolin and metalaxyl-m, and alternating these products with cyazofamid, was more effective compared to other fungicides in reducing PRRW and improving plant vigor. Our study identified effective fungicide treatment options for PRRW, allowing growers to alternate new chemistries with currently registered fungicides to reduce the risk of fungicide resistance development. • Phytophthora root rot and wilt (PRRW) symptoms were more severe on raspberry cultivars 'Meeker' and 'Tulameen' than in 'Cascade Bounty'. • Tank mix of oxathiapiprolin and metalaxyl-m alone or in combination with cyazofamid significantly reduced PRRW and increased plant vigor. • Fungicide treatments increased numbers of primocanes, floricanes (FC), weight of FC, and fruit yield. • Host resistance and fungicide applications can be integrated for PRRW management. [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).

Background: The population structure of crop pathogens such as Puccinia striiformis f. sp. tritici (Pst), the cause of wheat stripe rust, is of interest to researchers looking to understand these pathogens on a molecular level as well as those with an applied focus such as disease epidemiology. Cereal rusts can reproduce sexually or asexually, and the emergence of novel lineages has the potential to cause serious epidemics such as the one caused by the 'Warrior' lineage in Europe. In a global context, Pst lineages in Canada were not well-characterized and the origin of foreign incursions was not known. Additionally, while some Pst mating type genes have been identified in published genomes, there has been no rigorous assessment of mating type diversity and distribution across the species., Results: We used a whole-genome/transcriptome sequencing approach for the Canadian Pst population to identify lineages in their global context and evidence tracing foreign incursions. More importantly: for the first time ever, we identified nine alleles of the homeodomain mating type locus in the worldwide Pst population and show that previously identified lineages exhibit a single pair of these alleles. Consistently with the literature, we find only two pheromone receptor mating type alleles. We show that the recent population shift from the 'PstS1' lineage to the 'PstS1-related' lineage is also associated with the introduction of a novel mating type allele (Pst-b3-HD) to the Canadian population. We also show evidence for high levels of mating type diversity in samples associated with the Himalayan center of diversity for Pst, including a single Canadian race previously identified as 'PstPr' (probable recombinant) which we identify as a foreign incursion, most closely related to isolates sampled from China circa 2015., Conclusions: These data describe a recent shift in the population of Canadian Pst field isolates and characterize homeodomain-locus mating type alleles in the global Pst population which can now be utilized in testing several research questions and hypotheses around sexuality and hybridization in rust fungi., (© 2023. BioMed Central Ltd., part of Springer Nature.)