Dynamics of water-use efficiency and status in promising Hevea brasiliensis genotypes: implications for clonal selection

The rubber trees (Hevea brasiliensis) are exposed to water limitations in the Amazon region that can affect its physiology, making it necessary to select genotypes that are best adapted. This study analyzed the diurnal and seasonal changes in water use and status using traits of gas exchange and water relations in ten rubber tree genotypes in the immaturity phase from large-scale clone trials at three localities in the northwestern Colombian Amazon. In San Vicente del Caguán (semi-humid warm climate), the greatest means for water-use efficiency (WUEe and WUEi) and leaf water potential (ΨL) were observed, in contrast with Belén de los Andaquíes (humid warm) where there was a higher relative water content (RWC). Florencia (humid warm) presented high averages for WUEe and WUEi similar to San Vicente del Caguán. The WUEe and WUEi were greater in the dry season, contrary to those observed in ΨL and RWC. The WUEe was higher in the time range 9:00 to 12:00, while ΨL had a greater mean at 3:00 and a lower average at 12:00. In the dry season, the more efficient genotypes for water use had a higher leaf water potential as well as a lower relative water content, and had an extreme anisohydric behavior. In the wet season, these had a partial isohydric strategy. The FX 4098, MDF 180 and FDR 5597 genotypes were selected because of their greater adaptive capacity for water use and status, as compared to clone IAN 873 (control), which makes them desirable for future climate drought scenarios.