T. Bracci

In vitro olive (Olea europaea L.) cvs Frantoio and Moraiolo microshoot tolerance to NaCl

Abstract In vitro culture of rooted and unrooted olive microshoots, established from seed lines of free-pollinated “Frantoio” and “Moraiolo” cultivars, were evaluated for NaCl tolerance. The aim was to use growth and physiological parameters in order to identify salt-adapted genotypes. Leaf tissue elemental distribution of Na, Cl and K was also investigated in unrooted plantlets by cryo-scanning electron microscopy and energy-dispersive X-ray microanalysis. Both in unrooted and rooted plantlets, increased concentrations of NaCl reduced shoot growth, whereas plant survival was not affected. However, no significant interactions between line and NaCl concentration were found. Elemental distribution showed that Moraiolo J and Frantoio Z accumulated more Na and Cl inside leaves, and that these elements followed a tissue-dependent pattern. Rooting capacity was reduced at the higher levels of NaCl. Significant interactions between seed line and salt treatment were found. Seed lines showed different abilities to develop roots at different salt levels. In particular, Frantoio Z showed a significant and different behaviour relative to the other seed lines at 50 mM NaCl with regard to both length and dry weight of roots. The results obtained suggest that rooting parameters are the most useful tools in the evaluation and screening of salt-tolerant olive genotypes through in vitro shoot culture.

Chapter 2 – Olive Genomics

Publisher Summary Knowledge about genetic variability in the olive and the discovery of the genetic relationships between cultivars and wild genotypes are important tasks for germ plasm preservation and olive improvement. Unlike other crops, olive has conserved a wide genetic patrimony, across more than 1500 cultivars and in some wild populations around the Mediterranean basin. Efforts have initially been made to review the genus Olea and to colocate cultivated and wild olive trees in the Olea europaea complex. This analysis resolved all six subspecies within the complex as monophyletic groups, although some uncertainty remains for subspecies cuspidata, europaea and guanchica. Wild olive populations are a potential source of genetic traits for the improvement of cultivated forms and their genetic variability has been studied by multiple approaches. The results show that the population structure of wild olives from the north-western Mediterranean partially reflects the evolutionary history of these populations, although hybridization between wild olive and cultivated forms can occur in areas of close contact. The large number of cultivars present in all olive-growing countries raises several problems for germ plasm management and preservation. Evaluation and characterization of olive genetic resources is therefore crucial, since identification of cultivars is complicated by the large number of synonyms and homonyms and by the presence of clones.