1) Dr. Peter S. Searles – Keynote Presentation

To better understand the implications of climate change, the combined responses of olive trees to irrigation amount and warming need to be examined under desert conditions. Thus, the objective was to evaluate the effects of moderate deficit irrigation and warming during late winter and spring in arid Argentina on plant water status and reproductive development in young olive trees. Two irrigation and two temperature levels were applied to cultivars Arbequina and Coratina in open top chambers during the late winter and spring. The irrigation levels were 100% and 50% of irrigation needs, while the temperature levels were a near-ambient control and a warming treatment that was 4 °C above the control. The midday stem water potential generally decreased in both cultivars due to deficit irrigation and warming when applied individually, while an additive response was observed when both treatments were combined. In contrast, stomatal conductance was often reduced by deficit irrigation in both cultivars, but was little affected by warming. Moderate deficit irrigation did not significantly affect most reproductive variables. However, warming contributed overall to lower flowering intensity and fruit set or more parthenocarpic fruit, which led to yield reductions. From a production perspective, it does not appear that many early reproductive responses to high temperatures can be easily counteracted by adjusting irrigation under desert conditions. Further studies with more mature trees and cultivars over several growing seasons are recommended.