“Our varieties did well with the established players, but other businesses tended to be quicker to breed for resistance than we were,” says Trinette van Selling (Crop Breeding Manager Leafy Products). “It may have been a question of priorities. The push for improvement came in 2008, when we participated in an initiative of the Centre for Genetic Resources at Wageningen University & Research.” That year, a team of botanists travelled to Central Asia to collect wild spinach plants. Three years later there was a similar expedition to the Caucasus. Most of the wild species grow in these areas of origin, and there is a lot of genetic variation present. Van Selling: “This was also true with regard to resistances and resiliences to pathogens such as downy mildew. There was an urgent need for ‘fresh DNA’ to bring our resistance breeding to a higher level.”
And now it looks as if we have succeeded. 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 detailed work that had been done in previous years, they were able to make rapid tangible progress. 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.
Sales Representative Emmanuel Alcantar from California believes that for now, demand is only set to increase. "Our new varieties do have resistance to a new physiological race of downy mildew,” Alcantar explains. "This new race has caused a lot of problems for varieties with no resistance to it. All at once growers 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.” 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.”
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 Van Selling. “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.”
In many leaf 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 vulnerable 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 arms race between mutating pathogens on the one hand, and our breeders and other specialists on the other.”