Response of the clone RRIM 3001 (Hevea brasiliensis) to three ethephon stimulation treatments and the identification of differentially expressed transcription factors for a water-based stimulant

Abstract

Ethylene plays a role of gas hormone generated in response to varied stress in plant cells. In Hevea brasiliensis, periodic ethephon stimulation of tapped trees generates a dilution of the latex, a lower Total Solid Content (TSC) and a lower viscosity, resulting in a longer duration of the latex flow and a higher production of the following tappings. It also increases latex regeneration between two subsequent tappings. These mechanisms induce important changes in the laticifer metabolism and in the cellular genetic expression. Ethephon stimulation has become a major tool for tapping management. However, its excessive use can increase the susceptibility of trees to tapping panel dryness (TPD). A newly formulated ethephon water-based stimulant (RRIM HYDROBEST^TM, or RHB) is studied. A field trial was set with the clone RRIM 3001, comparing 4 stimulant treatments: ns = non-stimulated = control, ET = Ethephon 5%, MTX = MORTEX 5%, and RHB = RRIM HYDROBEST™ 5%. The production per tree was higher for MTX than for ns and ET, with RHB intermediate between both groups. The dry cut length (DCL) percentage of RHB was lower than that of ns, ET and MTX. Concerning the sucrose content of the latex measured in high-yielding and low-yielding periods, for the control ns alone, sucrose content in the low-yielding period was higher than that in the high-yielding period. Concerning the RHB treatment, in comparison with the control, 75 differentially expressed transcription factors were found, with most of them members of the ERF family. These results are discussed.