Breeding tools to prevent production losses caused by Erwinia:Reduced susceptibility/enhanced resistance to soft rot

Breeding tools to prevent production losses caused by Erwinia:Reduced susceptibility/enhanced resistance to soft rot


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Landbouw, Water, Voedsel>Sleuteltechnologieën LWV>Biotechnologie en Veredeling






Soft rot diseases are caused by a range of Pectobacteriaceae, mutually referred to as soft rot Pectobacteriaceae (SRP). Also in potato cultivation of these bacteria cause serious problems. Currently, cultivation and hygiene measures are the only means to deal with SRPs in potato. Still, in seed potato cultivation in the Netherlands SRP induced losses account for 22 M€ annually. Losses are due to downgrading and rejection of seed lots, soft rot during storage and costs to prevent SRP spread during harvest, storage and seed multiplication. The complexity of the SRP problem is caused by different Dickeya and Pectobacterium species and subspecies that can cause both latent and symptomatic infections. In addition, the SRP epidemiology is complex as the inoculum sources are diverse (seed tubers, flooding, aerosols, rain and insects) and the different plant organs show different susceptibility levels and symptoms (tuber soft rot, blackleg, slow wilt). Not surprisingly, breeding for resistance against SRPs has not been very successful, so far. For a successful breeding approach, all infection routes and stages should be taken into account.
In this project we will, for the first time pursue a combined approach to reduce susceptibility and to enhance resistance to SRP in potato. To reduce susceptibility, we will genetically determine why some varieties in the current breeding germplasm are more susceptible than others and develop tools to select against super-susceptibility in breeding programs. Secondly, we will target susceptibility (S) genes to enhance resistance and deploy them in non-GM way. Thirdly, we will deploy recently discovered SRE resistances from a wild potato plant. The genes underlying the reduced susceptibility and enhanced resistance will be introgressed and combined in cultivated potatoes. To accomplish these three goals, dedicated high throughput bioassay for the different infection routes and stages will be deployed and further developed.
This combined approach will generate plant material and unique insights in SRP pathogenicity, that can be applied directly in potato, and provides a model for SRP diseases in other crops. The total package of genetic improvement has never been applied before and will for the first time provide an outlook to potato varieties with SRP resistance. These varieties will be resilient to SRP infection and climate induced changes in pathogen population and will strongly contribute to robust novel agricultural systems like mixed and stripped cropping. Herewith, our research provides greater certainties and lower losses to seed potato growers, resellers, farmers and consumers. Reduced losses and efficiency inherently contribute to improved circularity, reduced energy input and CO2 emissions, thereby benefitting the entire society.

Doel van het project

Impact for breeding and crop protection research
Our combined approach will remove susceptibility and enhance resistance to a broad spectrum of SRP. Systemic spread of latent infection and exogenous infection like flooding, aerosols and insects will be blocked because all plant organs will be taken into account. Four groups of tools will be deliverables for the potato breeding sector:
• Novel and optimised assays to detect SRP susceptibility, and resistance responses
• Molecular markers to eliminate susceptibility from breeding germplasm
• S genes involved in SRP susceptibility in potato and potentially other crops
• Diploid potato material with mutated S genes and markers for s gene alleles.
• Diploid and tetraploid plant material and molecular markers to introgress resistance from S. chacoense
These tools will enable the potato breeders involved in the project to breed SRP resistant varieties within a few years in the case of diploid hybrid potato varieties. Breeding an SRP resistant tetraploid variety will take a few additional years. It is for the first time that such SRP resistant varieties can be made through a marker assisted breeding program.

Relatie met missie (Motivatie)

The SRP problem in the potato production chain has aggravated in recent years, as novel aggressive SRP became dominant probably due to climate change and host jumps. Associated with the transition to circular agriculture, which involves mixed and strip cultivation, a better understanding of pathogens affecting multiple crops is urgently needed. Knowledge about soft rot diseases, and the mechanisms causing host resistance or susceptibility will have general impact on breeding and protection research of SRP diseases in all crops. Applications of the knowledge generated in this project will directly reduce losses in potato production and on the longer run also in other crop systems. The private partners in this project are potato breeding companies. Providing seed tuber producers with the best varieties is their core business. This is a highly competitive market and it is a challenge to serve the client with the best adapted varieties possible. The resulting varieties will be marketed through the network of the partners. The success of each new variety depends on its added value over existing varieties. SRP resistance is a strong added value, but other variety characteristics must be equally competitive. Other variety characteristics aspects are beyond the scope of this project, but once these uncertainties are overcome and successful varieties with SRP resistance are available to the market, the impact will be profound. The deliverables for society will be:
• SRP resistant potato breeding material
Seed tuber lots from SRP resistant varieties will not be degraded prematurely. This will provide income, production and quality guarantees to all players in the production chain up until the consumers.
• Reduction of SRP infection pression in the agricultural landscape
The use of SRP resistant varieties will reduce the SRP pressure in the agricultural landscape. Alternative SRP hosts will benefit from it as well. In combination with the application of hygiene and cultivation practices, and seed testing programs, SRP free potato cultivation can be achieved on the long term.
• Cost and energy savings
Cost and energy reduction are expected along the entire potato production chain, as a strong reduction of losses is expected both pre- and post-harvest. Consequently, there will be a lower use of energy and CO2 emission.

Geplande acties

The innovative strength of this project is that we combine three resistance breeding strategies which have previously not been explored and combined.
1. Instead of selecting for resistance in current breeding material we will select against genes causing susceptibility. Candidate S gene identification will advance our knowledge about plant susceptibility that is relevant for other crop-pathosystems as well.
2. So far it was hard to deploy S genes to enhance resistance in potato because of the recessive character of S gene mediated resistance. Knock outs or knockdowns in GM plants were the only approach. Developments in diploid potato breeding allowed the development of an EMS mutation population. These S gene mutants can be deployed without the complications associated with GM.
3. We will enhance resistance through introgression of resistance from S. chacoense, a diploid wild relative of potato. We will study the S. chacoense mechanism that provides the resistance to multiple pathogen species in multiple organs. S. chacoencse is a diploid species which allows its resistance to be easily introgressed into diploid breeding programs. Through dedicated crosses we will also make the resistance available for tetraploid breeding.
4. Reduced susceptibility and enhanced resistance to SRP will be combined in advanced plant material allowing the breeding community to make SRP resistant varieties for the first time.

Naam projectleider

Jack Vossen