For expression measurements,the LightCycler 480 Software release 1.5.0,version
1.5.0.39 (Roche) was used and the expression levels relative to values of a reference sample were calculated using the Relative Expression Software Tool [38]. Normalization was performed using the expression levels of the ACTIN gene based on previous results [9]. The reference sample for expression was the expression value obtained for each variety for the sample collected in July (day 0 of the experiment), which was set to 1. Results were the average of four independent biological replicates.