Fantastic Downy Mildew Pathogens and How to Find Them: Advances in Detection and Diagnostics

Abstract

Downy mildews affect important crops and cause severe losses in production worldwide. Accurate identification and monitoring of these plant pathogens, especially at early stages of the disease, is fundamental in achieving effective disease control. The rapid development of molecular methods for diagnosis has provided more specific, fast, reliable, sensitive, and portable alternatives for plant pathogen detection and quantification than traditional approaches. In this review, we provide information on the use of molecular markers, serological techniques, and nucleic acid amplification technologies for downy mildew diagnosis, highlighting the benefits and disadvantages of the technologies and target selection. We emphasize the importance of incorporating information on pathogen variability in virulence and fungicide resistance for disease management and how the development and application of diagnostic assays based on standard and promising technologies, including high-throughput sequencing and genomics, are revolutionizing the development of species-specific assays suitable for in-field diagnosis. Our review provides an overview of molecular detection technologies and a practical guide for selecting the best approaches for diagnosis.

New insights from short and long reads sequencing to explore cytochrome b variants of Plasmopara viticola populations collected in vineyard and related to resistance to complex III inhibitors

“…Because the sequence error rate is expected to drastically drop for long reads in a near future, it should be possible to better detect and more rapidly characterize new cyt b resistant variants in natural populations, even when present at low frequencies. If ONT could revolutionize in-field downy mildew diagnostics and biosurveillance in the future [58], ONT long reads could also be a robust decision-support tool in fungicide treatments in vineyard, and more generally, for all plant of agricultural interest where resistance is associated with sequence modification.…”

Role of Some Essential Plant Oils, Fungicides and Inducer Resistance Elicitors on The Management of Cucumber Downy Mildew

“…Also, the key to doing so is using pathogen-specific systemic fungicides as soon as there is a danger of the pathogen being present. Broadly an integrated approach is important (Mc Grath, 2001;Lebeda and Cohen, 2011;Abada and Eid,2013;Holmes et al, 2015;Abada and Attia,2017;Patel et al, 2021;Salcedo et al, 2021 andRhouma et al,2022). Liebenberg et al (2005) evaluated in vivo the efficacy of selected plant extracts; neem (Azadirachta indica) derivatives (neem oil, neem cake powder and neem leaf powder) and the commercial fungicide Kocide DF, against bean rust.…”

Advances in molecular and optical detection strategies for grape downy mildew

“…The current marker system for P. viticola is designed using the internal transcribed spacer 1 (ITS1) and -5.8S rDNA to detect P. viticola as a general species (Valsesia et al 2005). The ITS region in downy mildew species known to be variable and often contain significant heterogeneity and insertions, making amplification challenging (Salcedo et al 2021). Within this study, new conserved amplification primers were developed along with a P. viticola sensu lato probe capable of detecting all pathogen types.…”

“…To understand inoculum load and mutations in a field found throughout a growing season, molecular detection methods using quantitative polymerase chain reaction (qPCR) and TaqMan probes are used. These tools allow for pathogen quantification as well as low-inoculum detection within fields for asymptomatic diagnosis (Salcedo et al 2021). Diagnostic tools are often paired with a method of disease sampling, like air or water collection, to understand pathogen levels across a site.…”