Obtaining Salt (Nacl) Tolerant Olive Plants: I) Some Physiological and Anatomical Characteristics of Olive Plants Growing in Harsh Saline Zones

Abstract

With the final aim of obtaining saIt tolerant olive plants, olive cvs. growing in the olive Germplasm Bank (World Collection) of Córdoba (Spain) (WC-CO) and plants growing in three harsh saline zones, each divided into two subzones, were selected. The zones and subzones were: "Odiel" River

SILVOLIVE, a Germplasm Collection of Wild Subspecies With High Genetic Variability as a Source of Rootstocks and Resistance Genes for Olive Breeding

“…The "Frantoio" (FRA) cultivar was the only elite olive variety exceptionally used as mother tree because of its potential interest in transmitting resistance to Verticillium wilt (Lopez-Escudero et al, 2004). The genotypes APR1 and ARC1 were previously obtained as seeds from salt-resistant wild olive trees present in Puerto Real (Cádiz, Spain) and Odiel (Huelva, Spain) salt marshes, respectively (Cantos et al, 2002). Seeds were surface-sterilized and germinated in-vitro in a hormone-free medium (Rugini, 1984) incubated in a growth chamber with 16 h light photoperiod (34 µM intensity with 70% red: 30% blue light-emitting diodes, LEDs, at 25 ± 2 • C. Seedlings were cut into uninodal segments and micropropagated in the same Rugini medium supplemented with 1 mg/L zeatin in the same growth chamber described before.…”

“…Wild relatives of the domesticated olive tree (Olea europaea L.) are evergreen, drought tolerant, usually multi-stemmed small trees or large shrubs with very good adaptability to different environmental conditions (Médail et al, 2001;Green, 2002;Kassa et al, 2019). Wild olives grow in arid and semiarid regions at different altitudes and soil types, including those exposed to severe water deficit, salinity and low temperatures (Cantos et al, 2002;Baldoni et al, 2006;Klepo et al, 2013;Belaj et al, 2016;Chiappetta et al, 2017). This adaptability to adverse environmental conditions makes wild olive trees suitable to grow in marginal soils (e.g., at risk of desertification), to colonize deforested habitats or to rehabilitate devastated regions (Bekele, 2005;Kassa et al, 2019).…”

“…A higher genetic diversity is still observed in the wild genepool (Lumaret et al, 2004;Baldoni et al, 2009;Belaj et al, 2010;Besnard et al, 2013a;Chiappetta et al, 2017;Kassa et al, 2019). Wild olives therefore represent an important source of genes for crop improvement of resistance to abiotic stresses [e.g., salinity (Cantos et al, 2002), water deficit (Hernández-Santana et al, 2019), soil pollution (Murillo et al, 2005)], vigor (León et al, 2020), crop yield and quality (Hannachi et al, 2008;Baccouri et al, 2011;León et al, 2018), as well as for resistance to biotic factors such as the Verticillium wilt (Colella et al, 2008;Arias-Calderon et al, 2015b;Trapero et al, 2015;Jimenez-Fernandez et al, 2016). Wild olive genotypes have been tested in limited breeding studies, showing potential to shorten the juvenile period or to increase flower production (Klepo et al, 2014), to improve oil composition (Hannachi et al, 2008;León et al, 2018) and to improve resistance to soil-borne diseases (Arias-Calderon et al, 2015a).…”

In Vitro Selection of Salt-Tolerant Olive Clones

“…Embryos from the two cultivated plants ("Galego" and "Lechín") growing in the World Olive plant Collection of Cordoba (Spain) in a non saline soil, presented lower germination and seedling formation than those from the plants growing in marshes and adapted to that harsh conditions (Cantos et al, 2002), but some embryos of the cultivated olive plants were able to form seedlings in the highest saline treatment and, on the contrary, some embryos of the plant growing in the salines soils dead in lower saline media. This behaviour showed the genetic variability of the olive embryo.…”

“…"Lechín" (both cultivated in the World Olive Plant Collection of Cordoba, Spain); other plant growing in "Raboconejo" in the River Odiel Marsh (Huelva, Spain), and other in "Lagolargo" in the Cadiz Bay Marsh (Cadiz, Spain). These last two areas are harsh salines marshes and consequently their olive plants are growing in high saline conditions (Cantos et al, 2002). Mature olive embryos were isolated as described by Acebedo et al (1997) and placed individually in test tubes (21x 150 mm) with 10 cc of the following culture media: 1/3 strength MS (Murashige and Skoog, 1962) with 5 gL -1 agar (control medium), and respectively the control medium plus 4, 6, and 8 gL -1 , equivalent to 68, 102, and 136 mM of NaCl.…”