311 Bud Source, Asepsis and Benzylaminopurine (BAP) Effect on Yacon (Polymnia sonchifolia) Micropropagation G. Mogor and A.F. Mogor G.P.P. Lima Plant Production Department, Agronomic Science College Biochemistry Department, Bioscience Institute Sªo Paulo State University (UNESP) Sªo Paulo Estate University (UNESP) Botucatu, Sªo Paulo, Brazil, cep 18.603-970 Botucatu, Sªo Paulo, Brazil, cep 18.603-970 Keywords: clonal propagation, cytokinin, oxidation, rhizophore, tissue culture, yacon Abstract The yacon (Polymnia sonchifolia) is used largely for the high fructan content of its tubers; consequently, it is a good alternative for diabetics. One of the more important restricting factors of the commercial production of yacon is its susceptibility to nematode attack. This, as well as germplasm bank maintenance, justifies the importance of in vitro propagation of this species. In this way, our work aimed to verify the best asepsis method for yacon for the in vitro establishment from the rhizophore and the axillary buds of the aerial parts, and the effect of benzylaminopurine (BAP) addition to the culture medium. The number of contaminated cultures, the occurrence of phenolic oxidation and the occurrence of a vitreous aspect, showed differences with bud source, immersion time for asepsis, and BAP use. The results contribute to establishing a yacon micro propagation procedure. INTRODUCTION Polymnia sonchifolia belongs to the Asteraceae (Compositae) family, and grows commonly in the Andes region (National Research Council, 1989). It was introduced to Brazil in 1991, in Capªo Bonito Country, Sªo Paulo State (Kakihara et al., 1997) and gave rise to economic potential because of the high fructan content of its tubers and its application in phytotherapy. The tubers contain inulin and are, therefore, a good alternative for diabetics (Lizarraga et al., 1997). The tubers are consumed naturally or processed, and the leaves, following drying, are consumed as tea (Vilhena et al., 1998). In the field, growers encounter difficulties in adapting their usual knowledge to yacon cultivation, although, satisfactory economic results are obtained. The extension services are supporting crop development and have identified the major problem in crop loss as the root-knot nematode (Meloidogyne incognita). It is estimated that a 30% increase in production is possible with the utilization of effective disease free seed pieces, as the first step towards a good yield. Tissue of numerous plant species have been cultured in vitro and became, consequently, free of pathogens (Hollings, 1965). The purpose of this study was to develop a technique for rapid clonal propagation of yacon by tissue culture, by evaluating a bud source, immersion time for asepsis and the effect of BAP addition to the culture medium. MATERIALS AND METHODS The experiment was carried out in the micro propagation laboratory of the Plant Production Department of the Agronomic Science College of UNESP in 1999. Buds, which emerged on rhizophores, were excised and washed with running water for five minutes; the same procedure was applied for shoot axillary buds. Disinfection was performed with a 20% aqueous solution of sodium hypochlorite, with two different immersion times, either 20 (treatment A) or 40 min (treatment) B. Twenty rhizophores and twenty-shoot axillary buds were submitted to treatment A, and the same number of buds were submitted to treatment B. All buds were placed on Murashige and Skoog medium (1962) with complete strength macronutrients and supplemented with 2 mg L -1 Proc. Int. Conf. on MAP Eds. J. BernÆth et al. Acta Hort. 597, ISHS 2003