Projectleader: Isaac Kwesi Abuley, Aarhus Universitet
Participants: Henrik Pedersen, AKV AmbA  Kim Hebelstrup, AU, Chris Khadgi Sørensen, AU, Olga A. Adrzejczak, AU, Jens Grønbech Hansen, AU og Charlotte Frederiksen, AKV AmbA
Start date: 01.12-2025
End date: 31-12-2028
Amount: kr 10.958.077,96

This project received funding from GUDP (grant Number: 34009-24-2267)

The Danish potato industry centres around starch potato varieties, covering approximately 45,000 ha, of which the starch variety Kuras occupies 27,000 ha due to its advantageous properties, such as high yield, (original) strong resistance to late blight, and drought tolerance. Unfortunately, Kuras has lost its resistance to late blight, making it highly susceptible and requiring increased fungicide use. Instead of replacing Kuras, we propose enhancing its resistance. Our project suggests R-gene rotation to extend the effectiveness of R-genes. To achieve this, we will create Kuras variants with distinct R-genes using precision breeding tools and determine the optimal rotation strategy to prolong the lifespan of these R-genes. By doing so, our aim is to reduce pesticide usage in Kuras cultivation and, consequently, within the potato industry. To realize this objective, our plan includes selecting effective and robust R-genes and mploying precision breeding to obtain kuras lines with combinations of several R-genes identified from wild accession; validating the durability of novel cultivars developed in this project; conducting histological studies on resistance mechanisms and response timing in the most robust novel varieties; and demonstrating the robustness of the novel varieties in the feld.

Expected outcome of the project
This project claims that Kuras can be improved and deployed effectively to prolong its resistance against late blight. By doing so, we will reduce the pesticide usage in Kuras and thus the potato industry. We aim at cutting the fungicide usage for late blight by ~86%.

Communication

• The outcome of the project will be communicated via various channels, including:
  • Peer-reviewed articles in open access journals.
  • News articles in growers’ journals. We will do a yearly communication of the project results to stakeholders (e.g. growers, consultants).
  • Presentation at relevant conferences (e.g. EuroBlight, EAPR, World Potato congress)
  • Workshops. The national potato workshop (e.g. Kartoffelworkshop) will be used to communicate the project findingds on yearly basis. Additionally, we will organise a "NGT-Kuras" workshop, inviting end-users and scientist to discuss the future of NGT and our results.
  • Open-field days will be organized at Flakkebjerg and Dronninglund from 2026-2028.
  • Demonstration days in 2027 and 2028
  • Regular update of the results will also be communicated via the project’s homepage

Timeline for communication result
Results will be communicated as soon available according to the project’s time plan (see milestones under work packages) and latest by the end of the project in 2028.

Work packages

WP 1: Precision breeding of R-genes in Danish potato varieties (Lead: Kim Hebelstrup, AU)
WP1 aims to create isogenic lines of the Kuras by introgression of R-genes shown in Appendix 1A and identified in the parallel project 'Opti-R' singly and stacked into the variety. WP1 involves the following tasks. Task 1: Cloning R-genes from wild Solanum species (Appendix 1B) that have been shown in the projects 'opti-R' and 'NovoCrops' to give strong and broad resistance to late blight. Task 2: Develop DNA vector constructs for the simultaneous transfer of up to five cis-genic R-genes. Task 3: Transform the variety of Kuras with each of the vectors. This will be done by transgenefree insertion of cis-genic R genes, which is a common NGT method. Task 4: Isogenic lines and the number of R-genes inserted will be confirmed by digital droplet qPCR and the insertion site will be confirmed by direct Sanger sequencing.

Milestones
M1.1:Cis-genic vectors constructed (M8)
M1.2:Isogenic lines of Kuras developed  (M12)
M1.3:Clonal propagation of each plant ready to be used (M14, 26, 38)
M1.4:Method report on the development isogenic lines of Kuras (M48)
M1.5:Manuscript on the improvement of resistance of Kuras to late blight via cisgenesis (M48)
M1.6 Manuscript on the improvement of resistance of Kuras to late blight via cisgenesis (M48)

WP2: Validation of the durability of novel cultivars under controlled and field condition (Lead: Isaac Kwesi Abuley, AU, co-lead: Charlotte Frihauge, AKV)
WP2 will evaluate the durability of WP1-developed cultivars against various P. infestans isolates and establish the minimum R-gene rotation period. Tasks include:

1. Assessing novel cultivar resistance against a range of P. infestans from DK and specific international clones.
2. Testing these cultivars against new P. infestans isolates from oospores.
3. Evaluating R-gene breakdown risk from inoculum on neighboring susceptible cultivars.
4. Testing variety robustness with other R-gene differentials in a trap nursery in two Danish locations, and in collaboration with the Horizon Europe project, IPMOrama, introducing a GIS-based national system to monitor trap nursery variety virulence.

Milestones
M2.1:Resistance of new varieties tested (M40)
M2.2:Optimal rotation of R-genes determined in greenhouse and field  (M40)
M2.3:Manuscript on the effectiveness of novel resistance genes to control late blight (M48)
M2.4:Manuscript on the optimal number of years an R-gene should be deployed before being rotated (M48)
WP3: Responses, timing and phenotypic classification of R-gene based resistance to potato late blight (Lead: Chris Khadgi Sørensen, AU)

WP3 aims to histologically study resistance mechanisms and response timing in the most robust novel varieties from WP1.
Greenhouse-grown potato plants will be drop-inoculated at varying growth stages and leaves will be sampled at different intervals. Histological staining and microscopy will reveal disease progression, pathogen structures, and host responses.

Milestones

M3.1:Microphenotypic classification of R-gene based resistance in potatoes against potato late-blight  (M48)

WP4 læggekartoffel opformering (Lead: Henrik Pedersen, AKV)
Den kommercielle produktion af læggekartofler starter med produktion af sygdomsfrie miniknolde, hvilket foregår ved eller under kontrol hos Tystofte fonden. Denne produktion tager et år og omfanget er typisk mellem 1.000 og 5.000 stk pr sort. Inden produktion af miniknolde kan finde sted, er det nødvendigt at sikre, at produktionen foregår ud fra sygdomsfrit materiale, og derfor skal der leveres 2-4 planter til Tystofte fonden, som bruger et (-to) år til sygdomstest.

Miniknoldene lægges herefter hos en autoriseret præbasis læggekartoffelavler, som første år dyrker kartoflerne under insektbeskyttende net, og derefter avlere videre på kartoflerne to år. Herefter køres produktionen videre hos autoriserede basisavlere, som typisk avler på materialet i to år, hvorefter der er salgsmateriale til melavlere.

Sideløbende skal sortens værdiafprøves, med henblik på optagelse på EU's sortliste over kartoffelsorter. Denne proces varer to år, og vil for type 1 kuras foregå i 2029 og 2030. De øvrige typer vil komme i årene herefter, når de er udvalgt, og der er tilstrækkeligt med lægge materiale til at foretage testene.

Det er en tidskrævende proces, og i projektperioden vil handlingerne at få de nye typer optaget i det danske meristem program og start produktion af præbasis læggekartofler kunne ske. Se appendiks 2 for detajleret opformeringsplan.

Milestones
M4.1:Production of new plants from stem cuttings (M15)
M4.2:Propagation of seed tubers (M20)

WP5 Markforsøg (Lead:Charlotte Frihauge, AKV)

Formål med forsøgsaktivitet er at sikre, at de nye Kuras varianter er meget tæt på den oprindelige kuras, hvilket indebærer, at der for kuras type 1 laves op til 10 linjer, hvor der over tre år laves en markudvælgelse, og der findes den linje, der vurderes bedst egnet.

Forsøgs aktivitet er begrænset af mængden af læggekartofler til anvendelse i forsøg. Derfor vil der ved AKV blive en produktion af læggekartofler, som er baseret på først opformering af antal planter ved dyrkning i potter, som efterfølgende vil blive dyrket i vækst tunneller under insekt og vindbeskyttende net.

År et vil der blive foretaget første skimmerresistens test baseret på få planter. År to vil der udover skimmel resistens test blive foretaget udbytteforsøg, hvor linjerne vil blive sammenlignet med den oprindelig kuras og andre standard sorter. År 3 vil der bliver foretaget test af skimmelresistens, udbyttemåling og strategiforsøg for fastlæggelse af  behov for skimmelbekæmpelse og skimmelresistensens styrke. Det er hensigten, at der skal foretages skimmelbekæmpelse ca. tre gange, men primært for at beskytte planten mod resistensbrydning i højrisiko perioder.

Milestones
M5.1:Field experiment done to test the robustness of developed varieties (M47)
M5.2:Demonstration of the fungicide reduction by using the new kuras (M47)
M5.3:On-farm trials (M48)

WP6: Project management and dissemination (Lead: Isaac Kwesi Abuley, AU, co-lead: Henrik Pedersen, AKV)
WP6 deals with project management

Milestones
M6.1:Kkick meeting  held (M1)
M6.2:Annual meetings held (M12, 24, 36, 48)
M6.3:Project workshop held  (M36, 47)
M6.4:Open field day held (M23, 47)
M6.5:Plan for Exploitation and Dissemination of Results (PEDR) (M7)
M6.6:Data Management Plan (DMP) (M7)