Blackleg Resistance – New Classification System

• the current R/MR/MS/S (resistant, moderately resistant, moderately susceptible, susceptible) ratings as a % of Westar will remain the same, refers to minor gene resistance
• a label to identify the major resistance genes in the variety will be added i.e. Resistance A to Resistance P (see chart below). This is a voluntary label extension at this time.

e.g. Canterra CS2100 rating is “R – ACG”, which describes a resistant  variety with 3 resistance groups containing major resistance  genes Rlm1 (or LepR3), Rlm3 and RlmS, respectively

• growers can proactively manage blackleg by rotating to a variety with a different letter(s), and therefore a different source of resistance