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Fusarium spp. are commonly associated with the root rot complex of soybean (Glycine max). Previous surveys identified six common Fusarium species from Manitoba, including F. oxysporum, F. redolens, F. graminearum, F. solani, F. avenaceum, and F. acuminatum. This study aimed to determine their pathogenicity, assess host resistance, and evaluate the genetic diversity of Fusarium spp. isolated from Canada. The pathogenicity of these species was tested on two soybean cultivars, 'Akras' (moderately resistant) and 'B150Y1′ (susceptible), under greenhouse conditions. The aggressiveness of the fungal isolates varied, with root rot severities ranging from 1.5 to 3.3 on a 0–4 scale. Subsequently, the six species were used to screen a panel of 20 Canadian soybean cultivars for resistance in a greenhouse. Cluster and principal component analyses were conducted based on the same traits used in the pathogenicity study. Two cultivars, 'P15T46R2′ and 'B150Y1′, were consistently found to be tolerant to F. oxysporum, F. redolens, F. graminearum, and F. solani. To investigate the incidence and prevalence of Fusarium spp. in Canada, fungi were isolated from 106 soybean fields surveyed across Manitoba, Saskatchewan, Ontario, and Quebec. Eighty-three Fusarium isolates were evaluated based on morphology and with multiple PCR primers, and phylogenetic analyses indicated their diversity across the major soybean production regions of Canada. Overall, this study contributes valuable insights into host resistance and the pathogenicity and genetic diversity of Fusarium spp. in Canadian soybean fields. [ABSTRACT FROM AUTHOR]

Effectors encoded by avirulence genes (Avr) interact with the Phytophthora sojae resistance gene (Rps) products to generate incompatible interactions. The virulence profile of P. sojae is rapidly evolving as a result of the large‐scale deployment of Rps genes in soybean. For a successful exploitation of Rps genes, it is recommended that soybean growers use cultivars containing the Rps genes corresponding to Avr genes present in P. sojae populations present in their fields. Determination of the virulence profile of P. sojae isolates is critical for the selection of soybean cultivars. High‐resolution melting curve (HRM) analysis is a powerful tool, first applied in medicine, for detecting mutations with potential applications in different biological fields. Here, we report the development of an HRM protocol, as an original approach to discriminate effectors, to differentiate P. sojae haplotypes for six Avr genes. An HRM assay was performed on 24 P. sojae isolates with different haplotypes collected from soybean fields across Canada. The results clearly confirmed that the HRM assay discriminated different virulence genotypes. Moreover, the HRM assay was able to differentiate multiple haplotypes representing small allelic variations. HRM‐based prediction was validated by phenotyping assays. This HRM assay provides a unique, cost‐effective and efficient tool to predict virulence pathotypes associated with six different Avr (1b, 1c, 1d, 1k, 3a and 6) genes from P. sojae, which can be applied in the deployment of appropriate Rps genes in soybean fields. [ABSTRACT FROM AUTHOR]

Introduction: Cranberry (Vaccinium macrocarpon) is an important crop grown in the United States and Canada, with the province of Québec being the world's largest producer of organic cranberry. However, cranberry fruit rot (CFR), caused by 12 fungal species, has become a major issue affecting yield. Methods: A molecular detection tool was used to detect the presence of the 12 CFR fungi and evaluate CFR species across three farms with different fungicide strategies in Québec. The incidence and frequency of CFR fungi were evaluated for 2020 and compared with 2018 data from the same farms in Québec. Machine-learning models were used to determine the possibility of explaining CFR disease and species based on climate, and analyze the effects of weather variables on CFR presence andprimary fungal species. Results: The most predominant CFR species remained the same in both years, with Godronia cassandrae and Coleophoma empetri being the two most common, but some species showed changes in relative abundance. Furthermore, this study examined the diversity variations in 2018 and 2020, with data showing an overall increase in diversity over the period. The results showed that fungicide applications impacted the species composition of CFR among the farms. Five weather variables (daily snow on the ground (cm), total daily precipitation (mm), daily atmospheric pressure (kPa), daily relative humidity (%) and daily temperature (°C)) were selected and found to contribute differently to the model with atmospheric pressure being the most important. Surprisingly, temperature and precipitations did not influence much the incidence of fungal pathogen species and each CFR species behaved differently in response to environmental factors. Discussion: Overall, this study highlights the complexity of predicting CFR disease, as caused by 12 fungi, and of developing effective disease management strategies for CFR. [ABSTRACT FROM AUTHOR]

The soybean cyst nematode (Heterodera glycines, SCN), is the most damaging disease of soybean in North America. While management of this pest using resistant soybean is generally still effective, prolonged exposure to cultivars derived from the same source of resistance (PI 88788) has led to the emergence of virulence. Currently, the underlying mechanisms responsible for resistance breakdown remain unknown. In this study, we combined a single nematode transcriptomic profiling approach with long-read sequencing to reannotate the SCN genome. This resulted in the annotation of 1932 novel transcripts and 281 novel gene features. Using a transcript-level quantification approach, we identified eight novel effector candidates overexpressed in PI 88788 virulent nematodes in the late infection stage. Among these were the novel gene Hg-CPZ-1 and a pioneer effector transcript generated through the alternative splicing of the non-effector gene Hetgly21698. While our results demonstrate that alternative splicing in effectors does occur, we found limited evidence of direct involvement in the breakdown of resistance. However, our analysis highlighted a distinct pattern of effector upregulation in response to PI 88788 resistance indicative of a possible adaptation process by SCN to host resistance. [ABSTRACT FROM AUTHOR]

Phytophthora sojae, the agent responsible for stem and root rot, is one of the most damaging plant pathogens of soybean. To establish a compatible-interaction, P. sojae secretes a wide array of effector proteins into the host cell. These effectors have been shown to act either in the apoplastic area or the cytoplasm of the cell to manipulate the host cellular processes in favor of the development of the pathogen. Deciphering effector-plant interactions is important for understanding the role of P. sojae effectors in disease progression and developing approaches to prevent infection. Here, we review the subcellular localization, the host proteins, and the processes associated with P. sojae effectors. We also discuss the emerging topic of effectors in the context of effector-resistance genes interaction, as well as model systems and recent developments in resources and techniques that may provide a better understanding of the soybean-P. sojae interaction. [ABSTRACT FROM AUTHOR]

The use of resistance genes in elite soybean cultivars is one of the most widely used methods to manage Phytophthora sojae. This method relies on effector‐triggered immunity, where a Resistant to P. sojae (Rps) gene product from the plant recognizes a specific effector from the pathogen, encoded by an avirulence (Avr) gene. Many Avr genes from P. sojae have been identified in the last decade, allowing a better exploitation of this type of resistance. The objective of the present study was to identify the Avr gene triggering immunity derived from the soybean resistance gene Rps8. The analysis of a segregating F2 progeny coupled with a genotyping‐by‐sequencing approach led to the identification of a putative Avr8 locus. The investigation of this locus using whole‐genome sequencing data from 31 isolates of P. sojae identified Avr3a as the likely candidate for Avr8. Long‐read sequencing also revealed that P. sojae isolates can carry up to five copies of the Avr3a gene, compared to the four previously reported. Haplotype and transcriptional analyses showed that amino acid changes and absence of Avr3a transcripts from P. sojae isolates caused changes in virulence towards Rps8. Functional analyses using CRISPR/Cas9 knockout and constitutive expression demonstrated that Rps8 interacted with Avr3a. We also showed that a specific allele of Avr3a is recognized by Rps3a but not Rps8. While Rps3a and Rps8 have been previously described as closely linked, this is the first report of a clear distinction hitherto undefined between these two resistance genes. [ABSTRACT FROM AUTHOR]

Abstract The yeast-like epiphytic fungus Pseudozyma flocculosa is known to antagonize powdery mildew fungi through proliferation on colonies presumably preceded by the release of an antifungal glycolipid (flocculosin). In culture conditions, P. flocculosa can be induced to produce or not flocculosin through manipulation of the culture medium nutrients. In order to characterize and understand the metabolic changes in P. flocculosa linked to glycolipid production, we conducted a 2-DE proteomic analysis and compared the proteomic profile of P. flocculosa growing under conditions favoring the development of the fungus (control) or conducive to flocculosin synthesis (stress). A large number of protein spots (771) were detected in protein extracts of the control treatment compared to only 435 matched protein spots in extracts of the stress cultures, which clearly suggests an important metabolic reorganization in slow-growing cells producing flocculosin. From the latter treatment, we were able to identify 21 protein spots that were either specific to the treatment or up-regulated significantly (2-fold increase). All of them were identified based on similarity between predicted ORF of the newly sequenced genome of P. flocculosa with Ustilago maydis' available annotated sequences. These proteins were associated with the carbon and fatty acid metabolism, and also with the filamentous change of the fungus leading to flocculosin production. This first look into the proteome of P. flocculosa suggests that flocculosin synthesis is elicited in response to specific stress or limiting conditions.

Silicon (Si) supplementation has been shown to improve plant tolerance to different stresses, and its accumulation in the aerial organs is mediated by NIP2;1 aquaporins (Lsi channels) and Lsi2-type exporters in roots. In the present study, we tested the hypothesis that grapevine expresses a functional NIP2;1 that accounts for root Si uptake and, eventually, Si accumulation in leaves. Own-rooted grapevine cuttings of the cultivar Vinhão accumulated >0.2% Si (DW) in leaves when irrigated with 1.5 mM Si for 1 month, while Si was undetected in control leaves. Real-time PCR showed that VvNIP2;1 was highly expressed in roots and in green berries. The transient transformation of tobacco leaf epidermal cells mediated by Agrobacterium tumefaciens confirmed VvNIP2;1 localization at the plasma membrane. Transport experiments in oocytes showed that VvNIP2;1 mediates Si and arsenite uptake, whereas permeability studies revealed that VvNIP2;1 expressed in yeast is unable to transport water and glycerol. Si supplementation to pigmented grape cultured cells (cv. Gamay Freáux) had no impact on the total phenolic and anthocyanin content, or on the growth rate and VvNIP2;1 expression. Long-term experiments should help determine the extent of Si uptake over time and whether grapevine can benefit from Si fertilization. [ABSTRACT FROM AUTHOR]

In plant–pathogen interactions, expression and localization of effectors in the aqueous apoplastic region play a crucial role in the establishment or suppression of pathogen development. Silicon (Si) has been shown to protect plants in several host–pathogen interactions, but its mode of action remains a source of debate. Its deposition in the apoplastic area of plant cells suggests that it might interfere with receptor–effector recognition. In this study, soybean plants treated or not with Si were inoculated with Phytophthora sojae and differences in the ensuing infection process were assessed through different microscopy techniques, transcript analysis of effector and defense genes, and effector (Avr6) localization through immunolocalization and fluorescence labeling. In plants grown without Si, the results showed the rapid (4 d post-inoculation) host recognition by P. sojae through the development of haustorium-like bodies, followed by expression and release of effectors into the apoplastic region. In contrast, Si treatment resulted in limited pathogen development, and significantly lower expression and presence of Avr6 in the apoplastic region. Based on immunolocalization and quantification of Avr6 through fluorescence labeling, our results suggest that the presence of Si in the apoplast interferes with host recognition and/or limits receptor–effector interactions, which leads to an incompatible interaction. [ABSTRACT FROM AUTHOR]

The soybean cyst nematode (SCN) Heterodera glycines and the oomycete Phytophthora sojae are among the most damaging pathogens of soybean worldwide. Resistant cultivars are commonly used to manage these diseases. As it is known that the presence of SCN can facilitate the development of other pathogens, it is important to verify if there is a synergistic activity between SCN and P. sojae. The purpose of this study was to evaluate a possible interaction on susceptible and resistant soybean lines. The plants were inoculated with one or both organisms at different stages (5 or 10 days old). Two levels of SCN inoculum (2,000 and 10,000 eggs/plant) and different timing between SCN and P. sojae inoculation (2, 5, or 8 days) were compared. The results on 5‐day‐old plants showed that SCN did not influence P. sojae development. The resistant cultivar to P. sojae remained effective (0% mortality) and susceptible cultivars exhibited high mortality (100%) in the presence or absence of SCN. Experiments on 10‐day‐old plants showed that SCN resistance was not affected by the presence of P. sojae. SCN inoculum density and timing of P. sojae infection did not affect the virulence of these pathogens and the efficacy of resistance genes. However, the number of SCN cysts was decreased by more than 50% (p <.001) when P. sojae was coinfesting the susceptible cultivar. This suggests that P. sojae might indirectly influence SCN development by reducing the root mass. This study confirmed that resistant cultivars remain a valid option for the management of P. sojae and SCN. [ABSTRACT FROM AUTHOR]