Abstract
Holm oak (Quercus ilex) is one of the most widely distributed tree species in the Mediterranean basin. High mortality rates have been observed in holm oak populations in the southwest of the Iberian Peninsula as a result of oak decline syndrome. Selection and propagation of genotypes tolerant to this syndrome could aid the restoration of affected areas. In this article, we report micropropagation and conservation procedures based on axillary budding and somatic embryogenesis (SE) of holm oak plants, selected for their tolerance to Phytophthora cinnamomi—the main biotic factor responsible for oak decline. Forced shoots were obtained from potted plants of eight different genotypes, and used as stock material to establish in vitro shoot proliferation cultures. Reliable shoot proliferation was obtained in seven out the eight genotypes established in vitro, whereas multiplication rates were genotype-dependent. The highest rooting rates were obtained by culturing shoots for 24 h or 48 h on rooting induction medium containing 25 mg L−1 indole-3-butyric acid, followed by transfer to medium supplemented with 20 µM silver thiosulphate. Axillary shoot cultures can be successful conserved by cold storage for 12 months at 4 °C under dim lighting. Shoot tips, excised from axillary shoot cultures established from tolerant plants, were used as initial explants to induce SE. Somatic embryos and/or nodular embryogenic structures were obtained on induction medium with or without indole-acetic acid 4 mg L−1, in two out the three genotypes evaluated, and induction rates ranged between 2 and 4%. Plantlet recovery was 45% after two months cold stratification of somatic embryos and eight weeks of culture on germination medium. Vegetative propagation of P. cinnamomi-tolerant Q. ilex trees is a valuable milestone towards the restoration of disease-affected areas.
Highlights
In the southwest Iberian Peninsula, Mediterranean oak woodlands occur as a particular anthropogenic habitat called “dehesas” in Spain or “montados” in Portugal [1]
High level contamination occurred in initial cultures derived from plants grown in the greenhouse, relative to plants forced to flush in the growth cabinet
Ascorbic acid was added to the culture medium, and the explants were moved to the opposite side of the test tube to mitigate this negative effect
Summary
In the southwest Iberian Peninsula, Mediterranean oak woodlands occur as a particular anthropogenic habitat called “dehesas” in Spain or “montados” in Portugal [1]. Dehesas are spaced oak woodlands in which a large part of the area is occupied by grassland managed as a savannah-like ecosystem [2] The evergreen oaks, such as holm oak (Q. ilex L) and cork oak (Q. suber L), are the main tree components of this agrosilvopastoral ecosystem and are of great socioeconomic and ecological importance in the SW Iberian Peninsula. Animals are an essential part of the dehesas, in which hunting species coexist with livestock species, such as cattle, sheep, goats, and pigs, that transform the production of grass, acorns and branches into products of premium quality and high added value (e.g., meat, including the internationally renowned acorn-fed Iberian ham, and cheeses) Another by-product of holm oak dehesas is the highly valued truffle or edible fungus [4]. The ecological importance of this ecosystem is indisputable, as it provides a multitude of advantages in terms of climate regulation, water provision, erosion control and carbon sequestration, among others [5]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
