Gene Expression under Short-Term Low Temperatures: Preliminary Screening Method to Obtain Tolerant Citrus Rootstocks

Climate change and global warming are leading to a change in weather patterns toward hot and cold waves. Citrus fruits are a tropical or subtropical crop whose growth is altered by changes in weather patterns. Thus, in the present work, two experiments are evaluated to obtain a screening method to select citrus rootstocks that help us to select new low-temperature-tolerant plant materials. One cold experiment was carried out with the Poncirus trifoliata and Citrus macrophylla rootstocks at 4 °C for 4, 8, 24 and 56 h. A second experiment was performed at 4 °C for 5 days with subsequent acclimatization lasting 0, 5, 10 and 24 h. The expression of the cold response genes CAMTA1, CAMTA3, CAMTA5, CBF1, ICE1 and COR413 IM1 was quantified. The results showed that the best rootstock selection strategy was the second experiment, as a higher expression of the genes CAMTA3, CAMTA5, CBF1 and COR413 IM1 was seen in the tolerant genotype P. trifoliata. We quantified the gene expression of proline biosynthesis P5CS1, dOAT and the proline transporters PROT1 and PROT2; the concentration of the amino acid proline in leaves was also quantified. These results once again showed that the best experiment to differentiate between tolerant and sensitive rootstocks was the second experiment with acclimation time.