Preliminary study of in vitro propagation of Austrocedrus chilensis

TACCARI, L.; VÉLEZ, M.L.; GRESLEBIN, A.G.; ROCHA, P.

Sapa

Congreso; 8th IUFRO working Party 7.02.09 Phytophthora in Foresta and Natural Ecosystems; 2017

IUFRO

Austrocedrus chilensis (patagonian cypress) is an endemic tree belonging to the Cupressaceae family found in Southern Argentina and Chile, across 140 000 ha in a wide variety of ecological niches and different soil types. In Argentina, it grows in a 60 to 80 km wide strip along the Andean foothills across a broad moisture gradient. In the west, A. chilensis can be found either in mixed stands with Nothofagus spp. or in pure stands on dryer sites. In the north, it can be found mixed with Araucaria araucana. It also grows in open, xeric forests or in isolated clumps at the limit of the Andean forest and the Patagonian steppe, acting as a barrier against desert advance. A. chilensis is valued not only because of its ecological function, also is one of the few native tree species with high potential to be planted for timber production. It grows relatively fast and the wood has been widely used since it is quite stable and appealing. Phytophthora austrocedri is a recently discovered pathogen that causes severe mortality of A. chilensis. Mortality was first registered in 1948 and the cause remained unknown until recently, which generated a deleterious effect on the native forests, which led the species to a serious threat of conservation. Individuals with different degrees of susceptibility to the pathogen are generally observed in affected areas. Since factors associated with the spread of the disease are difficult to control, detection and reproduction of tolerant/resistant individuals seems to be the best solution to the problem. At present, little work with almost no success regarding agamic reproduction of the cypress was done. The aim of this study was to contribute to the development of a micropropagation protocol. Seeds were collected from an open pollinated natural stands. Before use they were pre-chilled for 70 days. Seeds were submerged in 70% ethanol for seconds, and then the asepsis was performed with 25% sodium hypochlorite. After asepsis, seeds were stored in 1% w/v H2O2 to stimulate germination during 30 days. Embryos were extracted from the germinated seeds and incubated in a growth chamber at 24±2°C under a photoperiod of 16 h of cold light at a light intensity of 60 μmol?m-2?s-1. In the establishment stage the induction media employed was QL medium supplemented with the following combination of the growth regulators: Indole 3-butiric acid (IBA) (0.1 mg/l) and 6- Benzylaminopurine (BA) (1.5 mg/l). For callus induction QL was supplemented with 2,4-Dichlorophenoxyacetc acid (2,4-D; 3.0 mg/l). In all cases sucrose (30 g/l) and agar (8 g/l) were added, pH was adjusted to 5.70 ± 0.05, and media were sterilized by autoclaving. After 30 days of culture, the aseptic procedure performed in the laboratory was effective, showing low contamination (6.25%). Morphogenesis on explants was not induced in the media employed, with the balance and combination of growth regulators used. It is known that different proportions of cytokinins and auxins induce distinct responses according to their natural control in each plant. This was a preliminary study, new studies are necessary to determine the best balance of growth regulators, explant type, and culture conditions to induce organogenic or embryogenic tissue on explants of A. chilensis.