Citrus scion and rootstock combinations show changes in DNA methylation profiles and ABA insensitivity under recurrent drought conditions

The physiological, biochemical and molecular responses of scion/rootstock interactions in citrus plants under recurrent drought conditions are still poorly understood. The responses of 'Tahiti acid lime' (TAL) scions grafted to two rootstocks that have different survival strategies under drought conditions `Rangpur lime' (RL) and `Sunki Maravilha mandarin' (SM) were investigated during three periods of water deficit, WD1, WD2 and WD3 (plants exposed to one, two and three periods of water deficit, respectively). In the three drought periods, the Psi L was maintained at an average of -2.0 MPa. The TAL / SM and TAL / RL combinations showed, due to water deficit, hypermethylation and hypomethylation in the DNA methylation profiles respectively. The physiological parameters analyzed showed very close values for the TAL / SM and TAL / RL combinations, which indicates that the TAL does not respond to rootstock behavior with different response patterns to water deficit. Other findings suggest that the TAL scion is unresponsive to the plant hormone ABA, which plays a crucial role in plant responses to water deficit. The results show that the severity and recurrence of drought stress conditions reduced excessive ROS production through the action of the antioxidant enzymes, which confirms the different defense mechanisms to drought stress conditions that can be used by these scion/rootstock combinations. We concluded that the epigenetic marks they are involved in the responses to water deficit, conferring tolerance the citrus plants. In addition, in a recurrent water restriction condition the physiological parameters and the antioxidant system are genotype - dependent responsive. The present study addresses epigenetic modifications, physiological and biochemical mechanisms associated with drought tolerance in citrus plants.