Efficient in vitro shoot regeneration from mature apricot (Prunus armeniaca L.) cotyledons

• We report here an efficient and novel procedure to obtain direct shoot regeneration from the proximal zone of mature apricot cotyledons.
• This system worked for all genotypes tested, which makes this protocol a very interesting and useful tool.
• The dark incubation was critical for obtaining high regeneration efficiency from apricot stored cotyledons.
• The highest regeneration efficiency was obtained with TDZ (4 or 8 μM) and 0.25 μM IBA in combination with two weeks dark incubation.
• Regeneration pattern appeared as multiple shoots per cotyledon. Histological studies showed that epidermal and sub-epidermal cells of the cotyledon were the tissues from where direct organogenesis occurred.

Apricot (Prunus armeniaca L.) is widely considered as a recalcitrant species for shoot regeneration and genetic transformation. Previous reports indicated the possibility to obtain good regeneration from apricot hypocotyl slices; however, we report here an efficient and novel procedure to obtain direct shoot regeneration from the proximal zone of mature apricot cotyledons. Additionally, the system worked for all genotypes tested, which makes this protocol a very interesting and useful tool. Regeneration percentages were influenced by plant growth regulators and the initial dark incubation period, the former being critical to obtain high regeneration from stored apricot cotyledons. The highest regeneration percentages were achieved with TDZ (4 or 8 μM) and 0.25 μM IBA in combination with two weeks dark incubation period reaching up to 67.2%, 56.8%, 66.7%, 46.3% and 66.7% regeneration percentages for ‘Canino’, ‘Dorada’, ‘Moniquí’, ‘Real Fino’ and ‘ansu Maxim’ (Prunus armeniaca L. var. ansu Maxim), respectively. Regeneration pattern appeared as multiple shoots per cotyledon. Histological studies showed that epidermal and sub-epidermal cells of the cotyledon were the cells from where direct organogenesis occurred. To the best of our knowledge, this is the first report of direct in vitro regeneration from mature apricot cotyledons.