Disease resistence breeding

Our Spinach Breeder Johan explains

There is increasing pressure from consumers that no chemical pesticides be used in cultivation. In the process, breeders have to keep breeding for resistance to new diseases and pests but also to new strains and races of existing diseases and pests. Breeding new spinach varieties takes three to four years on average, as we can only do one cycle from seed to seed per year. However, it can be done even faster: we breed about five percent of our spinach on a fast track and can develop new hybrids in one to two years.

Resistance to the plant pathogen Peronospora effusa, which causes downy mildew, is the most important characteristic in spinach breeding. Why? In the U.S. alone, nearly half of baby leaf spinach is grown organically. Therefore, spinach varieties need the whole resistance package towards downy mildew, as growers are not allowed to use any fungicides. If growers don't use these full resistant varieties, the end product cannot be used, so as breeders we need to breed full resistant varieties. And when new variants of the downy mildew appear, the challenge is to develop new varieties more quickly than our competitors. In addition to baby leaf (salad) spinach in the U.S. and all around the globe, the other two main markets are the bunching spinach for the Asian markets and the processing frozen spinach concentrated in Northwest Europe.

Another challenge: Baby leaf spinach has a short lifecycle; sowing to harvest is sometimes just 25 days. This means that producers grow spinach in their fields more than once a year and some even year around. However, each time of the year the growing conditions are different, which places different demands on the varieties. We therefore need to breed different varieties for the different growing seasons. This is true for the bunching and processing markets as well. Therefore, our portfolio is growing fast: we introduce fifteen new varieties each year.

Spinach breeding is quite straightforward, as spinach is a wind pollinator. To develop a hybrid variety, which all our spinach is, we pollinate a female line with a male line. The challenge is to breed good female and male lines. For about the last ten years, a lot of effort has been put into the use of marker-assisted selection in the development of parental lines. Now this can be accelerated with our access to the laboratories in Einbeck, Most of our spinach breeding happens in the Netherlands, and we have breeding trials across the globe, depending on the market. For baby leaf we test in the U.S., Spain, Italy, UK, and many other countries across the globe. For the bunching markets we test mainly in China, Turkey, Korea and Japan. In Belgium, France, Germany and the Netherlands we test new spinach varieties for processing.