Induction of somatic embryogenesis in Araucaria araucana (Molina) K. Koch: considerations for ex situ conservation of ancient tree in Chile

Abstract

Araucaria araucana is an emblematic native conifer from Chile and Argentina that has been classified as threatened due to anthropogenic activities. Somatic embryogenesis (SE) is a biotechnological tool used for both the preservation of genetic material and the propagation of valuable genotypes. The present study investigates the effects of explant source and culture medium on SE induction in A. araucana genotypes from three wild plant populations. Immature strobili were collected from different geographical provenances: a coastal area (Villa Araucarias, “VA”), Cordillera de Nahuelbuta (Trongol Alto, “TR”), and the Andes Mountains (Malalcahuello, “MA”). SE induction was observed after 45 days in a basal medium (BM) supplemented with 1-naphthaleneacetic acid (NAA—11 µM), 6-benzylaminopurine (6-BA—2.8 µM), and Kinetin (Kin—2.8 µM). The highest induction rate (75%) was achieved for seeds from VA. Embryogenic cell line (ECL) proliferation requires auxins but is genotype-dependent, as not all genotypes survive. Cytochemical analysis revealed the presence of pro-embryogenic masses (PEMs) in the ECLs, indicating an efficient SE induction protocol. The progression of PEMs to early embryos was observed in the presence of maltose (3% w/v), polyethylene glycol 3350 (PEG—7% w/v), and abscisic acid (ABA—68 µM). Our results establish a baseline for the establishment of in vitro cultures for a diverse range of A. araucana genotypes, enabling the initiation of ex situ preservation programs and further investigation into embryo maturation.