Expression stability values (M) and ranking of the candidate reference genes as predicted by geNorm . Average expression stability values (M) were measured using stepwise exclusion of the least stable gene to organize candidate genes from the least (left) to the most stable (right). Different organs at three developmental stages (V4, R2 and R4). Developmental series in different plant organs (Root, Stem and Leaf). All organs and developmental stages together (Spatial/Temporal). Biotic stress treatments: Nematode-infected root (Nematode) and leaf infested with caterpillar (Insect). All conditions combined (Total).