The purpose of our research was to establish a protocol for the in vitro culture of Viburnum treleasei, a rare and endangered taxon with high ornamental potential endemic to the Azores islands. The surface sterilization of the explants was better achieved with a pretreatment of 0.1% (w/v) Benomyl for 2 h followed by 0.2% (w/v) HgCl2 for 10 min with agitation. Shoot tips were the most efficient explants for shoot development and single-node segments for proliferation. Woody plant medium (WPM) was adequate for all micropropagation stages. For culture establishment and shoot development, a hormone-free medium was adequate, whereas a 1.1 μM N6-benzyl adenine medium supplement was more efficient for shoot multiplication. Elongation and rooting could be carried out on a 1.3 μM 1-naphthaleneacetic acid-supplemented medium. Acclimatization of in vitro-produced plantlets was achieved after 1 month with a success rate of 50%. This in vitro propagation procedure will be useful for the conservation of Viburnum treleasei through production of morphologically true-to-type plants, allowing the recovery of depleted natural populations. Chemical names used: N6-benzyl adenine (BA); 1-naphthaleneacetic acid (NAA); HgCl2 (mercury bichloride).
Mónica Moura, Maria Irene Candeias and Luís Silva
Orlanda Cristina Barros Moreira, José Martins, Luís Silva and Mónica Moura
Prunus azorica is an Azorean endemic tree considered as a priority species for conservation. It is important as a laurel forest component, particularly at medium altitude, and as a food source for the endangered bird Pyrrhula murina. The best conditions for seed germination were investigated after removal of the outer layers of the fruit by determining the effect of 1) using stones or seeds; 2) stratification regime (six treatments and a control); 3) incubation temperature (four alternating temperature regimes); and 4) gibberellic acid concentration (three levels). This resulted in a fully factorial design with 168 (2 × 7 × 4 × 3) treatments with three replicates per treatment and 25 seeds per replicate. Cumulative germination percentages were determined at the end of the trial. Globally, there was a significant effect of endocarp removal (49% germination with seeds and 15% with stones). Both for stones and seeds, there was a significant effect of incubation temperature, stratification regime, and growth regulator concentration. Stones attained a maximum germination of ≈80% under several stratification treatments including cold (4 °C) or warm (20 °C) followed by cold and at 10/5 °C without the addition of a growth regulator. Seeds attained a maximum germination of greater than 90% without stratification at 10/5 or 15/10 °C without the addition of a growth regulator. During the stratification process, germination occurred only for seeds, particularly for longer treatments, for example, those corresponding to 3 or more months of stratification, including warm followed by cold (75% to 80%) or cold alone (77%). According to seed morphology and germination results, the seed appears to have a non-deep physiological dormancy. Seeds of P. azorica can thus be efficiently germinated after endocarp removal at temperatures of 10/5 or 15/10 °C with a daily light period of 12 hours. This protocol allowed producing hundreds of viable seedlings that were used in the reforestation of a laurel forest stand in a LIFE project.