Dutch courage: The potato covenant model shows the way

27 March 2020

Across the channel in the Netherlands a remarkable thing is happening. The whole supply chain has worked together through the ‘Potato Covenant’ to shift the organic potato sector to 100% use of robust, blight-resistant varieties.

Potato late blight (Phytophthora infestans) is the most important potato disease in the world. There has been a lot of effort gone into conventional breeding of blight resistant varieties. But, the introduction of novel cultivars often meets with … er…resistance as retailers’ and/or consumers’ awareness must be raised in order to open the market. Resistance is an important issue for farmers but not one that immediately resonates with consumers.

In the Netherlands the transition has been achieved in a remarkably short time. In 2017, there were only 3 blight-resistant potato varieties on the market. Now 22 ‘robust’ (blight resistant) organic potato varieties are on the market.

They say that ‘necessity is the mother of invention.’ In 2016 organic potato producers suffered massive losses due to late blight, with no recourse to copper fungicides which are completely banned in the Netherlands. Bionext, the Dutch umbrella organisation for the organic sector, recognised that the availability of resistant varieties needed to improve to prevent future disasters. Indeed, many organic farmers said that they would no longer grow potatoes unless they could use resistant varieties. Significantly, public outrage to the use of copper on organic potatoes forced the retailers to start moving. So, 28 organic potato breeders, growers and retailers came together to sign the covenant ‘Accelerated transition to robust potato varieties.’ The covenant partners agreed to give these robust varieties priority: in breeding, in production of seed potatoes, in potato cultivation and in sales.

Photo credit: Bionext

The covenant partners

  • Bionext, the Dutch umbrella organisation for organic food and agriculture and its members Biohuis, BioNederland and an association representing organic shops.
  • Retailers: Albert Heijn, Jumbo Supermarkets, Ekoplaza/Udea, Natural Stores/Natudis, Estafette Odin B.V.
  • Organic farmer organisations: Bdeko, Biowad, Association of Organic Farmers South West, Nedato cooperative, Dutch Organic Potato Pool.
  • Organic potato breeders: Agrico, HZPC, C. Meijer B.V., Plantera B.V., Den Hartigh, Europlant, Danespo, Caithness Potatoes B.V., Fam Vos, Carel Bouma organic potatoes B.V. and Plantum (the. Dutch association for the plant reproduction material sector)

How has this been achieved?

The covenant partners work closely with the Louis Bolk Institute and the Bio Impuls potato breeding project. The Bio Impuls programme (2009-2029), co-ordinated by Louis Bolk is aimed at breeding new blight-resistant potato varieties for the organic sector, working together with Wageningen University and Research, commercial breeders and farmer-breeders. The programme is funded by the Dutch Ministry of Economic Affairs. These varieties require only low nutrient inputs, and produce adequate yields and tasty potatoes. Every year 3 demonstration fields with all the robust varieties are set up and blight damage is monitored by Wageningen University. The demos are visited by farmers and covenant partners. Cooking and baking tests of the varieties are carried out and factsheets on blight management and practical instructions are offered to the farmers. An annual meeting of all the covenant partners is held and results are communicated through the media and workshops.

Most of the varieties have only one resistance gene which means that there is a serious risk for those varieties to lose their resistance in the future. Therefore, they are focused on raising farmers awareness of ‘resistance management,’ to ensure farmers actively check the crop and remove infected plants as quick as possible to make sure new phytophthora strains do not spread. The Bio Impuls project has new funding for the next 10 years (2020-2029) with one of the main goals to develop varieties with multiple resistance genes.

It has been a successful model, and in 2018 a similar covenant was signed in Flanders and Wallonia in Belgium. A key element for successful models is the involvement of ALL food chain partners and collaboration must be initiated from within the food chain. A neutral and skillful facilitator is needed who recognises and balances the different interests of all the parties involved.

So, why not the UK?

The organic market in the UK is very much driven by the multiple retailers who to a large extent dictate the varieties grown. There is very little diversity of organic potato varieties on the UK supermarket shelf. Variety choice is also a very real problem for the growers, especially to source organic seed. A large area of the blight susceptible Maris Peer is grown organically, due to the demands of the supermarkets. This makes it very difficult to grow without the use of copper fungicides. Last year the manufacturer of the copper-based fungicide Cuprokylt decided not to apply to Defra for a licence to market it in the UK, leaving growers without any alternative products for crop protection.

What’s more Maris Peer is not available as organic seed, so it needs a derogation from the organic control bodies. Cynics might suggest that this is a ploy by the packers to avoid expensive organic seed. The answer is not, in my opinion, to introduce resistance to Maris Peer through genetic modification, but to embrace the many blight-resistant varieties that are available - but it will need support from the market.

Sarvari Research Trust variety trial in Wales 2009. Photo credit: Phil Sumption

UK breeders of blight-resistant varieties the Sarvari Research Trust have struggled to break through in the commercial market, despite some of the excellent Sarpo varieties. Agrico have been selling a range of blight-resistant varieties under the Next Generation label appealing to both conventional and organic growers. Over the past 3 years the Soil Association has seen uptake of blight-resistant varieties increasing year on year. But, more needs to be done!

Wouldn’t it be great to see the organic control bodies come together with the growers’ organisations, breeders, researchers, multiples, packers and wholesalers to create a UK covenant and pathway to the greater uptake of resistant varieties? Let’s remove the resistance to resistance!

Phil Sumption - Bio Communications - carries out research communication for the Organic Research Centre.

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Header image: Selecting from second year clones at Biompuls’ field site in Klaggenburg. Photo credit: Biompuls

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Dutch courage or recklessness Blight resistance can be achieved with a limited number resistance genes. These were identified in wild potato species from the Andes. After decades of breeding (because organic growers cannot accept GMO) varieties like Sarpo Mira and these new Dutch varieties have entered the market. However, all these varieties have only a single resistance gene, and often the same one. If the blight pathogen evolves (mutates) and can evade recognition by the resistance of the potato, then this new virulent strain will infect several of these new varieties. In conventional cultivation some stewardship is recommended. A less frequent and low dosages application of fungicide helps avoid the evolution of resistance-breaking blight. This implies already a tremendous reduction of pesticide use. The organic sector cannot offer this stewardship, unless you would consider the use of copper. Anyway, the Dutch covenant partners banned copper. The best strategy is to continue to breed varieties with combinations of two or three of these R-genes. Such varieties have been made using GMO, but shelved due to lack of public acceptance. Compare this with three locks on your door. The probability that a mutant blight can by-pass one lock is considerable. The probability to by-pass multiple locks is negligible. Will breeders achieve such double or triple resistant varieties before the underlying resistance genes are worn-out, when using them as single layer of defence? The Dutch organic sector is recklessly offering single resistance genes as stepping stones for the pathogen, towards evolving complex virulence combinations. In that case those anticipated multi resistant varieties will have no added value against blight trained to break such locks. Because 2018 and 2019 were hot and dry summers, the Dutch have not seen big trouble. Dutch gamblers may lose decades of breeding effort and may also lose half of the available resistance genes, if 2020 brings a wet summer like 2016. Organic growers that cultivate varieties with new late blight resistance genes should respond to unhoped-for infection in their field with the same rigor as if this were the start of the exponential growth of a corona epidemic. Defoliation without delay is expensive, but you cannot imagine the gigantic amount of sporulation that emits from few infected plants.

When varieties with only a single major resistance gene would be grown on a large scale without any kind of protection nor surveillance, only then the Dutch breeders and farmers would be gambling away those precious resistance genes. However, that is not the case. Once again, the famous Dutch polder model is applied here as well, so together the stakeholders identified threats and possible solutions. With that, we use the current resistant varieties with a single gene untill the next series of varieties with two or more major genes is available. Breeders are working hard on that. Meanwhile the organic growers continue to scout their potato crops as if it where a susceptible variety, defoliating immediately when a suspicious plant is spotted. Non-organic growers are advised to spray these varieties some 3-4 times per season, just to be sure. With that, we are consciously safeguarding these new resistant varieties and the resistance genes incorporated, ensuring those genes are still effective when stacked with more resistance genes into the next series of varieties. So, to wrap it up, no the Dutch are not gambling away valuable resistance genes, no the Dutch are not sitting on their hands untill that next series is available, but yes, the Dutch are leading the way in shifting potato production away from ancient super-susceptible varieties and paving the way for new varieties carrying one or more resistance genes. That is not irresponsible, surely sensible and maybe even remarkable.

The information contained above reflects the views of the author/s and does not necessarily reflect that of Agricology and its partners.