OVARY AS VALUABLE EXPLANT FOR SOMATIC EMBRYOGENESIS INDUCTION IN GRAPES (VITIS SPP.)

Abstract

Somatic embryogenesis still needs to be improved for most agronomically important grapevine cultivars. Anthers are the explants generally used for grape somatic embryogenesis initiation, while ovaries are less frequently adopted. However, ovaries proved to be a suitable material for establishing somatic embryogenesis, as we obtained somatic embryos starting from these explants in several grape rootstocks (V. rupestris du Lot, Kober 5 BB, 110 Richter) and V. vinifera cvs. (Barbera, Brachetto a grappolo lungo, Chardonnay, Moscato bianco, Muller-Thurgau, Riesling). Flowers were collected in the vineyard 10 to 14 days before blooming, and both anthers and ovaries were plated on solid NN-based media added with 9 µM 2,4-dichlorophenoxyacetic acid (2,4-D) and 4.4 µM 6-benzyladenine (BA) (Medium A), or with 4.5 µM 2,4-D and 8.9 µM BA (Medium B), or with 5 µM 2,4-D and 1 µM BA (Medium C). Embryogenic callus was obtained from both anther and ovary cultures, with different efficiencies depending on genotype, explant type and medium, in most cases ovaries giving better results than anthers. No difference was noted in any aspect between embryogenic cultures originated from the two floral explants. Stable embryogenic cultures were preserved during a two-step culture: in the first step, callus propagation was obtained on the medium containing 4.5 µM 2,4-D and 8.9 µM 6-benzyladenine; in the second step, development of somatic embryos was induced within an additional two-month culture on an embryo differentiation medium supplemented with 10 µM 2-naphthoxyacetic acid, 1 µM 6-benzyladenine, 20µM indole-3-acetic acid and 2.5 g.l-1 activated charcoal. Somatic embryo maturation and individualization was obtained in NN-based liquid medium with 0.5 µM indole-3-butyric acid, while embryo conversion into plants occurred at satisfactory efficiencies when isolated somatic embryos were cultivated on a NN-based solid medium with 4.4 µM 6-benzyladenine and 0.5 µM indole-3-butyric acid. Plant micropropagation was performed in hormone-free NN medium.