Fusarium lettuce wilting: validation of a new race for harmonised use by the industry
Lettuce wilting is an important disease in production areas. Race 1 is presently used in DUS, and in 2016, a race 4 was observed and described for the first time. GEVES coordinated a project for validation of a differentials set allowing identification of races of Fusarium of lettuce in the framework of the Expert Group ISF DRT (Disease Resistance Terminology). After validation of Fol: 1, 2 and 3 races during the first ring tests, 2 new ring tests involving 13 participants compared different isolates of Fol: 4 on different differentials’ candidates, in tunnel and controlled conditions. This project allowed the definition of a reference isolate for Fol: 4 and of a differential set which were discussed and approved by the EG ISF DRT. An interpretation rule of the results of resistance testing with 3 levels : susceptible (S), Intermediate Resistant (IR) and Resistant (HR) was defined, allowing a harmonized description of varieties for the seed sector.