28 Sep 2015

New lettuce discolours less rapidly thanks to ‘Knox™’

Rijk Zwaan introduces a trait in its lettuce varieties that ensures that the leaves discolour pink less rapidly after cutting. The vegetable breeding company has nick-named the trait ‘Knox™’. Today, it presents this ground-breaking innovation during their Lettuce and Leafy Vegetable Conference in Antwerp, Belgium.

Main wish of the fresh cut companies

Knox extends shelf-life by about two days. According to Convenience Manager Bauke van Lenteren, the company directly responds to one of the main wishes of fresh cut companies with this development. “Knox ensures you do not necessarily need low-oxygen packaging for lettuce; this allows for lower costs and more options when blending. This means getting rid of the negative smell that is characteristic of opening low-oxygen packaging.”

Knox is also beneficial for the rest of the chain. For example, the extended shelf life gives retailers a better stock position and less waste. “It is self-evident that these benefits will also lead to a better end consumer experience. The consumer can enjoy the bag of pre-packaged salad for a longer time”, says Van Lenteren. “We expect Knox to lead to higher purchasing frequency, and therefore increased consumption of lettuce.”

Tried and tested

Rijk Zwaan worked on the development of Knox for a total of 10 years. The worldwide market leader in lettuce developed an assessment test in house in order to determine the presence of the trait, and then found it in a breeding greenhouse. The unique effect was confirmed in various laboratory tests and large scale factory trials. The property was subsequently crossed into various lettuce types as soon as possible.

Visitors to Rijk Zwaan’s ‘Leafy Event’ may view the first Knox varieties this week. About 10 varieties in different lettuce types now have this property. In collaboration with  growers and fresh cut companies , these varieties were successfully tested. Through their own crop advisor, growers worldwide may request trial seeds of these varieties. The expectation is that the range of Knox -based varieties will quickly be expanded in the next few years.


With its partners, Rijk Zwaan will be thinking on how to use the trait. “We want to make optimal use of Knox and the knowledge that we accumulated in the past few years. We will inform our partners accordingly as adequately as possible.”

“We are very proud of this introduction”, says Van Lenteren. “Not just due to the major benefits that Knox offers to the entire leafy vegetable chain right down to the consumer. Also due to the way in which we were able to achieve this break-through together with our colleagues and partners.”

New lettuce trait of Rijk Zwaan is Knox