Fungicides are integral to the fight against late blight in potatoes as the currently planted varieties are susceptible to the disease. Fungicide use is necessary, even for resistant varieties, to protect R-genes. Thus, the use of fungicides will remain key to controlling late blight. However, P. infestans can rapidly evolve to defeat the active ingredients in fungicides. The emergence of novel P. infestans genotypes (e.g., EU43, EU37) with reduced sensitivity to notable fungicides restrains our ability to manage the disease effectively and sustainably. Therefore, it is necessary to understand the development of fungicide resistance and develop suitable mitigation strategies. So, the project aims to understand the sensitivity of P. infestans populations to the fungicides used in Denmark, design markers to monitor fungicide resistance, understand the drivers of fungicide resistance development, and devise suitable anti-resistance strategies to mitigate them. Towards this goal, we will study the sensitivity of P. infestans to key fungicides in DK and ascertain other traits that enable the establishment of fungicide-resistant strains (WP1); develop and validate markers for mutations responsible for resistance to mandipropamid (WP2); identify the drivers (e.g., dosage) for the development of fungicide resistance and develop anti-resistance strategies to mitigate fungicide resistance (WP3); establish and implement a long-term fungicide resistance monitoring plan with stakeholders in the potato industry to ensure the continuous monitoring and early detection of fungicide resistance to the existing fungicides for controlling late blight (WP4). The project will contribute to the sustainable management of fungicides.
WP1 aims to ascertain the sensitivity of Danish and European P. infestans isolates to key fungicides in DK. Additionally, WP1 will measure other traits (e.g., aggressiveness, virulence) that enable the establishment of new variants of the pathogen. Lead: Isaac K. Abuley, AU
Task 1.1. Sampling of isolation of P. infestans in Denmark. On FTA cards (dead) for genotyping and live samples for genotyping and phenotyping. Collaboration with James Hutton Institute, Scotland
Task 1.2. Fungicide sensitivity analyses (cyazofamid, fluazinam, mandipropamid, oxathiapiprolin, cymoxanil, propamocarb). DK isolates + selected isolates from other EU countries. Collaboration with James Hutton Institute, Scotland
Task 1.3. Studies to determine other traits that enable the invasion of resistant strains. resistant and sensitive strains will be selected and tested for aggressiveness (i.e., lesion size, latent period and sporulation capacity), and virulence against commonly grown and new varieties, and selected differentials with known resistance genes, incl. Black’s R1-R11.
Deliverables
D1.1. Sensitivity of novel P. infestans genotypes to key fungicides in Denmark (Report) (M12)
D1.2. Other traits enabling the establishment fungicide resistance strains (Report) (M18)
D1.3. Fungicide sensitivity, aggressiveness, and virulence of novel Phytophthora infestans genotypes (M26) (Peer-reviewed article)
WP2 deals with studies to find mutations that could be responsible for the mandipropamid-resistant strains. This WP will focus on only mandipropamid as the potential region for mutation is already known, thus making marker development within the project’s lifespan feasible. Lead: Isaac K. Abuley, AU
Task 2.1: Studies to find mutation in the CeS family of genes for mandipropamid-resistance. We will select isolates that are resistant (n = 10) and sensitive (n = 10) to mandipropamid from WP1 and sequence the PiCesA3 gene as described previously. Develop a marker - G1105S substitution.
Task 2.2: Evaluation of marker performance. The marker developed in Task 1.1 will be tested for detecting mutations in resistant (n = 10) and sensitive isolates (n = 10). The validated marker will be used for screening for resistance to mandipropamid in the later stages of the project.
Task 2.1: Studies to find mutation in the CeS family of genes for mandipropamid-resistance. We will select isolates that are resistant (n = 10) and sensitive (n = 10) to mandipropamid from WP1 and sequence the PiCesA3 gene as described previously. Develop a marker - G1105S substitution.
Task 2.2: Evaluation of marker performance. The marker developed in Task 1.1 will be tested for detecting mutations in resistant (n = 10) and sensitive isolates (n = 10). The validated marker will be used for screening for resistance to mandipropamid in the later stages of the project.
Deliverables
D2.1 Development of a marker for detecting mutation in the PiCeSA3 gene (M18)
D2.2 Evaluation of the performance of the marker for detecting resistance to mandipropamid (M20)
D2.3 Marker-assisted detection of reduced sensitivity to mandipropamid (Peer-reviewed article) (M30)
WP3 will primarily focus on the development of anti-resistance strategies regarding mandipropamid and fluazinam. However, the broader goal is to achieve a prolonged effective lifespan of all the available fungicides for managing late blight. Lead: Isaac K. Abuley, AU
Task 3.1 In vitro studies to find the effective anti-resistance strategies. Fungicide mixtures / BCA & PRI. Two varieties with different host resistance
Task 3.2 Whole-plant assay to test different anti-resistance strategies. Whole-plant assay (WPA) will be done in two varieties (resistant and susceptible) to investigate the effect of alternation, mixing, and inoculum density on the selection of resistant strains for both fluazinam and mandipropamid
Task 3.3 Field experiments to validate anti-resistance strategies. Field experiments will be carried out at three locations (Dronninglund (CS2), Arnborg (CS3) and Flakkebjerg (CS5) in 2024 and 2025 to validate the most promising anti-resistance strategies.
Deliverables
D3.1 The sensitivity of fungicide-resistant strains to fungicide mixtures in vitro (M15)
D3.2 Test of different anti-resistance strategies in the whole-plant assay (M20)
D3.3 Test of different anti-resistance strategies in the field (M18, M30)
D3.4 Fungicide resistance avoidance strategies in potato late blight management (M35) (Peer-reviewed article)
This WP is premised on the fact that continuous monitoring of fungicide resistance in the pathogen population is a key to early detection and mitigation against the establishment of resistant strains. While this project will generate a key understanding of the fungicide resistance situation in DK, there is a need to establish a business plan and a stakeholder driven infrastructure for continuous monitoring of the key elements of ICM – including understanding and prevention of pathogen adaptation to fungicides mode of action and host resistance. Lead: Jens G. Hansen, AU
Task 4.1 Stakeholder engagement to develop long-term fungicide monitoring plan
Task 4.2 Workshop 1 physical training on anti-resistance strategies, DK stakeholders. Workshop 2 (online) - Invite relevant EuroBlight partners
Deliverables
D4.1 Joint statement on long-term fungicide resistance monitoring plan (M30)
D4.2 Presentations from workshop 1 (M18)
D4.3 Presentations from workshop 2 (M10)
This WP will aim to create a conducive platform for project management, results dissemination, and communication. Lead: Jens G. Hansen. AU
Task 5.1 Website, Intranet, Communication and project management / Teams Intranet
Task 5.2 Project meetings. One physical project meeting and one virtual meeting inviting all partners to be accomplished each year. Virtual technical meetings according to the need.
Task 5.3 Data management plan (DMP) and plan for dissemination and exploitation of results (PEDR)
Deliverables
D5.1 Project website, intranet and user manual (M2)
D5.2 Minutes/notes from project meetings (M2, M11, M23, M35)
D5.3 Data management plan (M6 and update in M31)
D5.4 Plan for dissemination and exploitation of results (M6 and update in M31)
D5.5 Final project report (M36)
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