The aim of this study was to evaluate the variation in the expression levels of five traditional housekeeping genes under contrasting conditions of abiotic stress to identify the most stable reference gene. In the evaluation of expression levels by RT-PCR, the gene with less variation among cultivars and treatments was the ribosomal 26S. Regarding to the variation between foliage and root tissues the more stable genes were â-tubulin and 26S, while between phenological stages the best were 26S and the 1-â elongation factor. The evaluation of expression levels by absolute qPCR confirmed that the 26S gene is a stable reference for the study of gene expression based on the PCR technique due to its low coefficient of variation through contrasting abiotic stress conditions.
