The company's specialist for convenience & leafy salads Bauke van Lenteren said: "It extends the shelf life of a bag of pre-packed lettuce by around two days, which opens up new opportunities for the whole chain.
"Processing companies no longer need to pack the lettuce in low-oxygen bags, plus they have more options to create blends of several different types."
He added: "We first revealed KNOX at our Leafy Event in September but it's now time for us to present this innovation to a wider audience. 2016 is going to be a key year of testing and trials for the KNOX varieties."
Currently around 10 varieties have been bred with the trait, with more in development, Rijk Zwaan has said.