Proceedings of the XLVI Italian Society of Agricultural Genetics - SIGA Annual Congress

Giardini Naxos, Italy - 18/21 September, 2002

ISBN 88-900622-3-1

Poster Abstract - 4.58

VALIDATION OF A PROTOCOL FOR LILY PLANT REGENERATION VIA SOMATIC EMBRYOGENESIS

TRIBULATO A.

Dipartimento di OrtoFloroArboricoltura e Tecnologie Agroalimentari (DOFATA), Sezione Ortofloricoltura - Università degli Studi di Catania, Via Valdisavoia 5, 95123 Catania

Lilium, secondary embryogenesis, embryos germination, propagation, growth regulators

To achieve as final goal cut flower and potted plant production, cropping chain in lily goes from propagules output through bulbs growth, bloom programming and forcing of bulbs in the greenhouse. All the different steps are connected by temporal and functional links, thus failing of one phase could compromise optimal qualitative characteristics of the produce. For a better efficiency of the production chain, tissue culture, besides being involved in breeding programs, is widely spread for bulblets mass propagation. However, during propagules production the risks to regenerate somaclones or plants holding chimerical traits may occur depending on the adopted regeneration protocols. In this frame, despite the need to improve propagules quality, direct somatic embryogenesis could be considered as a suitable morphogenic process to produce true-to-type plants.

The assessment of a protocol to induce somatic embryogenesis in ‘Star Gazer’ was previously reported at the DOFATA, of which morphogenic process, especially for the above reasons, seemed to be worthwhile of further investigations. Thus, an experimental design was set up using the Oriental hybrid ‘Alliance’, with the aim to confirm our previous results, to better investigate on starting material and to focus on plant production process following induction of somatic embryogenesis. Flower pedicel transversal sections (3-5 mm thick) were cultured on MS medium, 30 g/l sucrose, 3 g/l gelrite and added with dicamba or picloram 2 or 6 µM. Twelve weeks from culture onset, the attention was paid on somatic embryos germination; they were excised from mother explant and placed to either MS medium added with picloram 6 µM or MS hormone-free medium.

After eight weeks from culture onset, somatic embryogenesis occurred upon the different culture conditions on the epidermis of flower pedicel sections. Moreover a decreasing embryogenic rate was detected along the flower pedicels, according to the distance from the receptacle; overall the 74,1 % of embryogenic explants was obtained for the sections nearest to receptacle, against the 22,9 %, of sections close to the stem. Embryos germination and plantlets formation was performed on all culture conditions, although best results were achieved on MS hormone-free medium with 89 % of somatic embryos which underwent germination; on this culture condition, secondary embryogenesis occurred from primary embryos, thus resulting on a number of regenerated plantlets higher than the plated somatic embryos.

In conclusion, performing in ‘Alliance’ plant regeneration following direct somatic embryogenesis, validated our protocol characterised by both high embryo yield and germination rate. Up to know, knowledge on regeneration pathways of Oriental lilies via direct somatic embryogenesis is based on treating flower pedicel sections with either dicamba or picloram. A decreasing regeneration rate was detected for explants distant from the receptacle. A possible explanation to discuss this result could be based on tissues age and polyploidisation after cells differentiation and expansion; in our case a number of explants from pedicel parts proximal to the stem might have undergone endoreduplication which is often linked with inhibition of somatic embryogenesis. A further step to verify our protocol for plant breeding and propagation purposes will be the investigation, through biotechnological and bioagronomical approaches, on the effective genetic stability of regenerated plants.