Abstract

Cactus pear (Opuntia ficus-indica: Ofi) and pitahaya (Hylocereus undatus: Hu) are fruit producing CAM species. Because (i) CAM species exhibit high water use efficiency (WUE: dry mass production/transpiration) and (ii) the fruits from Ofi and Hu are valued in the local and export fresh and processed fruit markets, these species have been proposed as a water-saving strategy for fruit production in arid zones. The aim of this study was to quantify the WUE efficiency of Ofi and Hu under the local conditions of the semi-arid fruit production zone of Chile and compare it to the WUE of C3 fruit trees adapted to this zones. We established a two-year trial in which we planted one year old plants of Ofi, Hu, pomegranate (Punica granatum: Pg), fig (Ficus carica: Fc) and tamarillo (Cyphomandra betacea: Cb) in 50 L pots containing perlite. The substrate was covered with plastic in order to avoid evaporation. The plants were drip irrigated and the pots weighed before and after each irrigation in order to estimate transpiration. At a 20 day interval, during the two growth seasons (september-may), three plants per species were uprooted and their dry mass obtained. The slope of the relationship between cumulated dry mass and cumulated transpiration of each species was considered as the WUE. Thereafter, WUE was normalized by DPV in order to generate values which could be extrapolated to other zones. Our results showed that Ofi and Hu had similar WUE of 18.6±1.3 and 16.5±1.4 g[DM] kg-1[H20], respectively, which were significantly higher, by an average factor of 5.3, than Fc and Pg (WUE = 3.4±0.1 and 3.2±0.1 g[DM] kg-1[H20], respectively). Cb, on the other hand, had significantly lower WUE than the rest of the species with a value of 2.5±0.2 g[DM] kg-1[H20], in the typical range of other C3 fruit trees. These results confirm that CAM are excellent water saving species for arid zone fruit production and can save between 80 and 85% water per unit dry mass as compared to C3 fruit tree species.