453 Proc. IV IS on In Vitro Cult. & Hort. Breeding Eds. S. Sorvari et al. Acta Hort 560 , ISHS 2001 INFLUENCE OF GELLING AGENTS ON ILEX PARAGUARIENSIS TISSUE CULTURE P.A. Sansberro, H.Y. Rey, C.V. Luna and L.A. Mroginski IBONE.C.C. 209. (3400) Corrientes Argentina e-mail: ibone@espacio.com.ar Keywords : Ilex paraguariensis, tissue culture, gelling agents Abstract The effect of seven gelling agents (Agar A-1296; Agar A-9799; Agar A-7921; Agarose A-0169; Agargel A-3301, Transfergel T-5660, and Phytagel P-8169. All of them from Sigma Chemical Co.) on different in vitro tissue culture systems of Ilex paraguariensis was studied. Interactions were found between type of agar and plant regeneration. The type of agar, being Phytagel significantly better than Agar (A-1296) affected somatic embryogenesis by in vitro culture of immature embryos. However, Agargel promoted induction of callus from leaves, while Phytagel was the best gelling agent for callus growth. Although, the type of gelling agent did not affect the in vitro establishment of nodal segments, the multiplication phase as well as the rooting of regenerated shoots was greatly increased by Phytagel. Phytagel was also found to be the more adequate gelling agent for in vitro maturation and germination of immature zygotic embryos. l. Introduction The "mate tree" (Ilex paraguariensis St. Hil.), a perennial tree belonging to the family Aquifoliaceae is an economically important crop of some regions of South America (Northeast of Argentina, Paraguay and South of Brazil). Its leaves are used for making a stimulatory beverage named "mate". The potential of plant cell and tissue culture techniques for improvement of Ilex paraguariensis has been extensively discussed (Mroginski, et al. 1997). Successful establishment of explants depends on the medium composition (Rey, et al. 1991; Mroginski, et al. 1999; Sansberro, et al. 1998) as well as on proper explant selection (Bernasconi, et al. 1996; Sansberro, et al. 2000). In all cases media solidified with agar were employed. It has many advantages, however, agar is not a standard product (Debergh, 1983; Beruto, et al. 1999b) and can affect the growth and the developmental of the tissues (Scholten and Pierik, 1998b). In this study, we compared the effects of seven different gelling agents on the growth and development of tissues of Ilex paraguariensis cultured in vitro. 2. Materials and methods Establecimiento Las Marias, Virasoro, Corrientes, Argentina kindly provided plants of Ilex paraguariensis. Nodal segments culture was performed as was previously reported (Sansberro, et al., 2000). The medium for establishment consisted of quarter strength Murashige and Skoog (1962) with 3 % sucrose –1/4MS- lacking hormones. For multiplication the medium was 1/4MS + 1 mg/L Benzylaminopurine. Rooting of regenerated shoots was accomplished with 114MS lacking hormones. The protocol of Sansberro, et al. (1998) has been employed for in vitro culture of rudimentary embryos. The medium was 1/4MS + 0.1 mg/L Zeatin. The procedure described by Rey, et al. (1991) has been used by callus induction from leaf explants. The