Cryopreservation and optimization of in vitro germination of Handroanthus serratifolius

Abstract

Handroanthus serratifolius is a tree species with wide distribution in Brazil which may be used as ornamental plant. It is propagated by seeds which loose viability within a short period. This study aimed to (i) test different thawing periods for cryopreserved seeds, (ii) evaluate the germination rate, fresh and dry weights of the seedlings, and (iii) optimize the in vitro germination process. Seeds were placed in a Falcon tube (15 ml) and stored in liquid nitrogen for three days prior to thawing for 1, 3 or 5 min in a water bath at 38±2°C. For in vitro germination, the seeds were decontaminated in 70% alcohol for 30 s and NaOCl (2% active chlorine) for 10 min followed by inoculation (P1) or their embryos were extracted, decontaminated in NaOCl (1% active chlorine) for one minute and inoculated in MS medium containing 0.5 ml-1 GA3 (P2). After decontamination, embryos were inoculated on MS medium containing 0.5 mg L-1 GA3. After 30 days, the germination percentage and the shoot length of seedlings originated from both procedures (P1 and P2) and the fresh and dry weight (mg) of shoots and roots of seedlings originated from P2 were evaluated. A significant difference between the decontamination procedures tested regarding germination (p<0.0001) was observed. Only 10% of seeds subjected to P1 after 30 days culture germinated compared to 95% of germinated embryos subjected to P2. Significant difference (p=0.0001) in the fresh weight between shoots and roots was observed, regardless the thawing period. Regarding dry weight, a significant difference was observed between shoots and roots (p=0.0002) and among thawing periods (p=0.0269). The results show that one minute thawing is effective for cryopreserved embryos.