Strategies for olive (Olea europaea l.) breeding: Cultivated genetic resources and crossbreeding

Abstract

Olive cultivars represent an invaluable heritage of genetic variability selected over more than 5500 years of cultivation. This high diversity of local cultivars is a common feature in traditional olive-producing countries. Most cultivars are old and continue to be cultivated around areas where they have likely been selected. Crossbreeding in olives was only initiated in the second half of the twentieth century and currently represents the most promising strategy to provide farmers with new cultivars that are well adapted to the new high density olive plantations spreadingin traditional and new olive-growing countries. This chapter focuses on cultivated genetic resources and crossbreeding strategies in olive. Exploration, cataloguing and authentication for the conservation and sustainability of true-to-type cultivars by morphological and DNA markers in the Network of Germplasm Banks promoted by the International Olive Council, is the most extensive and worldwide initiative to date. The strategies, methodologies and advances in crossbreeding programs worldwide are reviewed. Shortening the juvenile period, early selection and other strategies for the evaluation of valuable agronomical traits are integrated into the framework of alternative protocols that also provide information regarding the variability and heritability of these traits. In addition, the possibilities provided by new genomics tools to shorten the protracted crossbreeding process are also presented. Finally, new developments on in vitro culture and genetic transformation as well as the feasibility of using these tools in breeding programs are discussed.