After years of intensive research and breeding, the Dutch vegetable seed company Rijk Zwaan is launching two Romaine lettuce varieties for the US market with a resistance against the Impatiens necrotic spot virus (INSV). These varieties are the first in the company’s INSV Defense line. “We are really excited that we can support lettuce growers and processing companies with this breakthrough. For them, this can make the difference between profit and loss,” state Johan Schut and Christophe Thomas from the Rijk Zwaan breeding team.
$100 million estimated damage
For growers in the Salinas Valley, the USA’s key lettuce-producing area, INSV (and TSWV) – which are transmitted by the western flower thrips – has been a serious problem in 2020, 2021, and 2022. The economic impact of the damage in 2020 alone was estimated at over $100 million.
TSWV resistance also effective against INSV
For the Rijk Zwaan team, the INSV Defense story began back in 2005, when they started working to find resistance against the Tomato spotted wilt virus (TSWV). Johan Schut, Breeding Manager Lettuce: “That was the start of a classical breeding journey including the use of advanced techniques like DNA markers. When INSV was first found in California in 2012, we conducted tests in the lab and found that our trait also worked against INSV.” The urgency increased when the problems in the Salinas Valley worsened in 2020. By then, the breeding teams in France, the Netherlands, and the US were at an advanced stage of selecting Romaine lettuce varieties.
49 field trials in the past two years
Over the past two years, the US team in Salinas and several dealers have run a total of 49 field trials. These trials confirmed that the selected varieties FARMIN RZ and JAMMIN RZ had high resistance (HR) against INSV. These Romaine lettuce varieties also show good agronomical performance, being well adapted to the US requirements.
More INSV-resistant lettuce varieties in the pipeline
Pelleted seeds of both Romaine varieties will be available in early 2023. “We are excited to be able to support lettuce growers and processing companies, especially in the US market. We expect to launch INSV Defense varieties of all lettuce types in the future,” states Breeder Christophe Thomas.
Rijk Zwaan