Average expression stability values (M) calculated by geNorm.

<p>The genes are ranked according to their expression stability; the least stable genes are on the left, and the two most stable genes are on the right. The samples are divided into sub-groups: (A) susceptible plants of cv. Celeia; (B) resistant plants of cv. Wye Target; (C) plants infected with <i>Verticillium albo-atrum</i>; (D) control (non-infected) plants; (E) plants evaluated 10 days post inoculation with fungi; (F) plants evaluated 20 days post inoculation with fungi (G) plants evaluated 30 days post inoculation with fungi (H) all plant samples.