María Paz Suárez

Effect of moderate high temperature on the vegetative growth and potassium allocation in olive plants

There is little information about the prolonged effect of a moderately high temperature on the growth of olive (Olea europaea L.). It has been suggested that when the temperature of the air rises above 35°C the shoot growth of olive is inhibited while there is any reference on how growth is affected when the soil is warmed. In order to examine these effects, mist-cuttings and young plants generated from seeds were grown under moderate high temperature (37°C) for 64 and 42days respectively. In our study, plant dry matter accumulation was reduced when the temperature of both the air and the root medium was moderately high. However, when the temperature of the root medium was 25°C, the inhibitory effect of air high temperature on plant growth was not observed. The exposure of both the aerial part and the root to moderate high temperature also reduced the accumulation of K+ in the stem and the root, the water use efficiency and leaf relative water content. However, when only the aerial part was exposed to moderate high temperature, the accumulation of K+ in the stem, the water use efficiency and leaf relative water content were not modified. The results from this study suggest that the olive is very efficient in regulating the water and potassium transport through the plant when only the atmosphere surrounding the aerial part is warmed up. However, an increase in the soil temperature decrease root K+ uptake and its transport to the aerial parts resulting in a reduction in shoot water status and growth.

Strategies for Olive (Olea europaea L.) Breeding: Cultivated Genetic Resources and Crossbreeding

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 spreading in 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.