Effects of drought stress and climatic conditions on Olea europaea L. physiology and fruit set

Production of olive oil in the State of Texas is a relatively young yet rapidly expanding industry. Climates in several parts of Texas closely resemble semi-arid areas in which olive trees (Olea europaea L.) are cultivated worldwide. However, there is little research to date on physiological responses of olive cultivars grown in Texas to drought stress and influences of climate on flowering date and fruit retention. Researchers conducted a 2010-2011 study to evaluate changes in physiological response in 4 cultivars of greenhouse grown olive trees when exposed to three irrigation treatments (high, medium, and low; irrigated daily, every other day, and every fourth day, respectively). This study also sought to identify climate, location, and cultivar effects on flowering date and fruit retention in several existing Texas olive orchards. Results indicate cultivars ‘Arbequina’ and ‘Koroneiki’ were most able to maintain levels of physiological response, in terms of photosynthetic rate, stomatal conductance, and water use efficiency across all irrigation levels. Additionally, there were few significant differences between high and medium irrigation treatments overall. However, differences were found between medium and low treatments. Studies also indicate location and cultivar had an effect on fruit load. Olive orchards located farther south in the state flowered earlier in the year and retained fruit more effectively throughout the growing season. ‘Arbequina’ also set and retained at least a small amount of fruit across every orchard in which it was planted.