CRISPR/Cas9 gene editing technology has taken the scientific community by storm since its development in 2012. First discovered in 1987, CRISPR/Cas systems act as an adaptive immune response in archaea and bacteria that defends against invading bacteriophages and plasmids. CRISPR/Cas9 gene editing technology modifies this immune response to function in eukaryotic cells as a highly specific, RNA-guided complex that can edit almost any genetic target. This technology has applications in all biological fields, including plant pathology. However, examples of its use in forest pathology are essentially nonexistent. The aim of this review is to give researchers a deeper understanding of the native CRISPR/Cas systems and how they were adapted into the CRISPR/Cas9 technology used today in plant pathology—this information is crucial for researchers aiming to use this technology in the pathosystems they study. We review the current applications of CRISPR/Cas9 in plant pathology and propose future directions for research in forest pathosystems where this technology is currently underutilized.

Our experience is that FEES guides appropriate and safe diet recommendations in this population.

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Motivation The ability to develop robust machine-learning (ML) models is considered imperative to the adoption of ML techniques in biology and medicine fields. This challenge is particularly acute when data available for training is not independent and identically distributed (iid), in which case trained models are vulnerable to out-of-distribution generalization problems. Of particular interest are problems where data correspond to observations made on phylogenetically related samples (e.g. antibiotic resistance data). Results We introduce DendroNet, a new approach to train neural networks in the context of evolutionary data. DendroNet explicitly accounts for the relatedness of the training/testing data, while allowing the model to evolve along the branches of the phylogenetic tree, hence accommodating potential changes in the rules that relate genotypes to phenotypes. Using simulated data, we demonstrate that DendroNet produces models that can be significantly better than non-phylogenetically aware approaches. DendroNet also outperforms other approaches at two biological tasks of significant practical importance: antiobiotic resistance prediction in bacteria and trophic level prediction in fungi. Availability and implementation https://github.com/BlanchetteLab/DendroNet.

Invasive plant pathogenic fungi have a global impact, with devastating economic and environmental effects on crops and forests. Biosurveillance, a critical component of threat mitigation, requires risk prediction based on fungal lifestyles and traits. Using a machine learning approach that separates phylogenetic and genomic feature signals, we analyzed 387 fungal genomes to test the hypothesis that there are predictive signatures associated with phytopathogenic lifestyles and traits. Our results lend strong support to this hypothesis, and our analyses uncovered genomic patterns associated with phytopathogenic lifestyles and traits, identifying gene families that are potentially important in the evolution of plant pathogenic fungi. We found that the top-performing feature sets for predictions included carbohydrate-active enzymes (CAZymes), peptidases, and secondary metabolite clusters. Expansions in the number of CAZyme and peptidase genes, and of specific families such as CBM63, were revealed in the genomes of plant pathogens compared to non-phytopathogenic genomes (saprotrophs, endo- and ectomycorrhizal fungi) and were strong predictors of phytopathogenicity. Such genomic feature profiles could be useful to predict risks of fungal plant pathogens in future biosurveillance activities.

Invasive exotic pathogens pose a threat to trees and forest ecosystems worldwide, hampering the provision of essential ecosystem services such as carbon sequestration and water purification. Hybridization is a major evolutionary force that can drive the emergence of pathogens. Phytophthora ramorum, an emergent pathogen that causes the sudden oak and larch death, spreads as reproductively isolated divergent clonal lineages. We use a genomic biosurveillance approach by sequencing genomes of P. ramorum from survey and inspection samples and report the discovery of variants of P. ramorum that are the result of hybridization via sexual recombination between North American and European lineages. We show that these hybrids are viable, can infect a host and produce spores for long-term survival and propagation. Genome sequencing revealed genotypic combinations at 54,515 single nucleotide polymorphism loci not present in parental lineages. More than 6,000 of those genotypes are predicted to have a functional impact in genes associated with host infection, including effectors, carbohydrate-active enzymes and proteases. We also observed post-meiotic mitotic recombination that could generate additional genotypic and phenotypic variation and contribute to homoploid hybrid speciation. Our study highlights the importance of plant pathogen biosurveillance to detect variants, including hybrids, and inform management and control.

Invasive exotic pathogens pose a threat to trees and forest ecosystems worldwide1, hampering the provision of essential ecosystem services such as carbon sequestration and water purification2. Hybridization is a major evolutionary force that can drive the emergence of pathogens3. Phytophthora ramorum, an emergent pathogen that causes the sudden oak and larch death, spreads as reproductively isolated divergent clonal lineages. Sexual recombination has never been reported in this pathogen under natural conditions and laboratory crosses have yielded unfit progenies, suggesting postzygotic barriers to hybridization. Here we report the discovery in a plant nursery of novel variants of P. ramorum that are the result of homoploid hybridization via sexual recombination between North American and European lineages of the pathogen. We show that these hybrids are viable, can infect plants and produce spores for long-term survival and propagation. Genome sequencing revealed novel genotypic combinations, not present in the parental lineages, at 54,515 single nucleotide polymorphism loci. More than 6000 of the novel genotypes at these loci are predicted to have a functional impact in genes associated with host infection, including effectors, carbohydrate-active enzymes and proteases. We also observed post-meiotic mitotic recombination that could generate additional genotypic and phenotypic variation and contribute to homoploid hybrid speciation. Our study highlights the importance of plant pathogen biosurveillance to detect novel variants and inform management and control.