Luis Rallo

Dormancy release dynamics in olive tree (Olea europaea L.) reproductive buds as affected by cold accumulation, tree bearing status, and budburst temperature was studied under natural and controlled conditions, using both cuttings and container- and field-grown plants. The chilling necessary for dormancy release was acquired at different times within the bud population, presenting a progressive pattern of reproductive budburst. Once sufficient chilling is accumulated, 20 °C is a suitable temperature for reproductive budburst, although higher temperature, e.g., 30 °C, during dormancy release can inhibit budburst. While the bearing status of trees determined the amount of return bloom, dormancy release followed a similar pattern for previously bearing and non-bearing trees. Concurrent with investigating budburst factors, the use of shoot cuttings was tested as a method for olive dormancy release studies by contrasting with results from whole trees. It was found it to be valid for studying reproductive budburst, thus providing a useful method to screen chilling requirements in cultivar evaluation and the breeding programs currently ongoing in this species. However, the method was not valid for vegetative budburst, with varying results between cuttings and the whole plant.

The olive ( Olea europaea ) and table olive industries worldwide are almost entirely supported by low-density rain-fed orchards planted with local cultivars empirically selected by farmers for centuries. New early and high-bearing plantation systems adapted to mechanical harvesting have been designed and developed during the past 50 years. Only certain traditional cultivars are well suited for these new olive plantations. The new orchards therefore require new cultivars. A long-term effort on the exploration, conservation, and sustainable use of olive genetic resources starting in Spain in 1970 has been followed by breeding programs developed since the early 1990s by the University of Cordoba, the University of Seville, and the Andalusia Institute for Agricultural, Food and Fisheries Research. We are trying to use crossbreeding to obtain new early bearing cultivars adapted to mechanically harvested orchards. Objectives related to shortening the juvenile period (JP) and developing early tests of selection, early bearing, high cropping, resistance to chief diseases (particularly verticillium wilt caused by Verticillium dahliae ), industrial suitability, high oil content, diversity of olive oil composition for oil cultivars, and fruit size and quality for table olive are being pursued. Specific criteria for the adaptation of oil olive and table olive cultivars to mechanical harvesting, such as low-vigor trees with a compact growth habit, the force needed for fruit removal, natural fruit abscission, resistance to bruising, and extending the harvest time in cultivars showing homogeneous ripening are evaluated in the progenies. To date, more than 19,000 seedlings have been initially evaluated, 481 preselections are on intermediate field trials, and 31 advanced selections are being established in a network of field trials. A new protected cultivar Sikitita (Chiquitita in the United States), selected for very-high-density narrow hedgerows, was released in 2008. Recently, a first project on olive genomics is heralding the use of marker-assisted selection in the midterm phase of development. Cultivars adapted to the new mechanical harvest systems will be progressively released in the future.