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9 months ago

The Partnership no. 18

Constant arms race In

Constant arms race In many leafy crops, downy mildew is notorious for its ability to develop new strains or physiological races, and to overcome mostly monogenic resistances in plants that are the result of crossings. Lettuce, in fact, has more than 20 known physiological races; spinach has around 17. Growers have no use for varieties that quickly succumb to downy mildew. As a result, spinach breeding has always been highly resistance-driven. Van Selling: “Whenever a new physiological race shows up, and resistant varieties turn out to be susceptible again, a new genetic response needs to be found and crossed in. Of course, it has to include all the other positive traits that a grower expects from varieties. It is a constant rat race between mutating pathogens on the one hand, and our breeders and other specialists on the other.” In 2015, the breeding programme was given an extra boost, thanks to the combined efforts of the new spinach breeder Jan Dijkstra and molecular biologist Faira Zuidgeest. With the benefit of the breeding work that had been done in previous years, they were able to make rapid tangible progress. This resulted in several new varieties, which have been tested extensively in the past two or three years and measure up well against competitors. Two of these are now on the rise in the Southwestern United States. Small plant, big crop “Spinach is a very important crop here,” explains Sales Representative Emmanuel Alcantar from California. “The main production areas are California in spring and summer and Arizona in the winter period. Some 70,000 acres are cultivated every year. Due to the early harvesting stage, seeds are sown very close together. It is estimated that seed consumption for spinach in our country is almost 250 billion units per year.” That sounds attractive, but a logical consequence is also that it should be inexpensive and perform well. In addition, all those seeds must be produced first. This means that varieties can be successful only if they perform well in long-term seed production, in addition to having an excellent practical value for growers, processors and consumers. In that respect, resistances to the diverse leaf and root diseases are even more important. Market segments Depending on the targeted use, we broadly distinguish between two types of spinach. The Smooth Type is the norm for the fresh market, although the demand for savoy types in this segment is increasing. Cultivation for the processing industry is dominated by the Savoy Type. Alcantar: “The difference is in the texture of the leaf. The Smooth Type has slightly smoother leaves with a fine texture that are very tender. The Savoy type is somewhat coarser, which is no problem at all for the processing industry. It also has a higher yield, so the yield per acre is a lot higher. Most of the commercial varieties are suitable for both fresh-cut and processed market segments.” Nature remains fickle Based on the excellent results of the field trials in 2018 and 2019, last winter and spring Enza Zaden launched two new varieties (Trail Boss and Crosstrek) with an improved resistance pattern. Since then, these have been picked up by multiple growers. The Sales Representative expects that this demand will only increase for the time being. In the meantime, it has become clear that varieties, originating from a seed company with an excellent reputation in spinach breeding, has proved to be susceptible to a new physiological race of downy mildew in the winter-spring growing season. “Those varieties probably has little resistance to a new physiological race of downy mildew, while our new varieties do have resistance,” Alcantar explains. “It is actually really sad to see. All at once you have to write off fields of spinach with large percentages of diseased plants. Of course, it is wonderful that our varieties do seem to be resistant to the new strain of mildew. So far we are not seeing any damage in California. We’ll have to wait and see how they do in Arizona, but it does build some confidence.” Product “It is estimated that seed consumption for spinach in our country is almost 250 billion units per year.” Emmanuel Alcantar Alcantar points out that nature is fickle, and it is impossible to predict whether you will be able to repeat this year’s success next year. “The fact remains that Enza Zaden has established itself very well this year. As a result, I expect we’ll gradually be able to expand our market share - all the more since there are a few bright stars in the current trials again. We would like to introduce the first one very soon.” Organic and indoor farming In the United States, organic cultivation is gaining ground in many crops. When asked if this also applies to spinach, Alcantar says: “I would estimate the share of the organic cultivation at about 40%. You have to get to know the varietal material really well before you can get a good seed crop. That takes time. But we are of course working on that together with our organic subsidiary, Vitalis.” For now, the priority in spinach breeding is expanding the existing portfolio. "There is a great need for fast-growing winter varieties, so we are focusing especially on that," says the Crop Breeding Manager. “We are also seeing an increasing demand from indoor farming. Plant factories with artificial light are not a large market yet but are definitely a rapidly expanding segment - with its own very unique needs and challenges. Now that we also have good research facilities for this market, we can and will respond even more effectively.” 6 | The Partnership The Partnership | 7

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