A TWO-STAGE MICROPROPAGATION SYSTEM FOR CRANBERRIES

A two-stage micropropagation system was devised for cranberries (Vaccinium macrocarpon Ait.). Shoottip explants taken from four cultivars of greenhouse-grown plants were placed on media composed of Anderson’s major salts, Murashige and Skoog’s (MS) minor salts and organics, plus various concentrations of 2iP, IBA, and GA3. In other experiments, explant source, salt formulations for media, and rooting treatments were studied. Optimal multiplication and shoot quality occurred when nodal explants taken from greenhouse-grown or micropropagated plants were placed on medium containing 150 μM 2iP, 1.0 μM IBA, and no GA3. Histological examination revealed that the initial response of nodes to culture is axillary bud proliferation, but adventitious shoot formation occurred after 4 to 6 weeks. Cultures that contained only axillary shoots were not evident unless low levels of 2iP were used, at which point only axillary buds present on the explants were released. Proliferated shoots could be rooted ex vitro without auxin treatment. Optimal rooting occurred under high-light conditions. Plants were transplanted to the field for comparison to conventionally propagated material. Chemical names used: gibberellic acid (GA3), N-(3-methyl-2butenyl)-1H-purin-6-amine (2iP), 1H-indole-3-butanoic acid (IBA). The value of the U.S. cranberry crop has risen dramatically in the last few decades (Eck, 1990). In 1986, a record U.S. farm value of $190 million was achieved when more than 166,000 t of fruit was produced. Cranberries are mainly grown in Massachusetts and Wisconsin on ≈4500 and 3200 ha, respectively (Eck, 1990). Although cranberries area high-value crop, tissue culture technology lags far behind in comparison to other Vaccinium species. For example, procedures for micropropagation and/or adventitious shoot regeneration have been reported for highbush blueberries (V. corymbosum) (Billings et al., 1988; Callow et al., 1989; Chandler and Draper, 1986; Wolfe et al., 1983), lowbush blueberries (V. angustifolium) (Frett and Smagula, 1983; Nickerson, 1978), and rabbiteye blueberry (V. ashei) (Lyrene, 1980). Preliminary work on cranberry (V. macrocarpon) tissue culture has been reported. Scorza et al. (1984) concluded that the herbicide glyphosate, alone or in combination with 2iP, increases axillary shoot formation in cultured cranberry nodes. However, proliferation rates were fairly low (5 to 7 times), and the ability to subculture or root the shoots was not reported. Most recently, Serres et al. (1990) presented data that suggest the stable expression of a foreign gene, introduced into cultured cranberry stems via particle acceleration technology. Cranberries are commercially propagated by pressing stem cuttings into freshly sanded bogs where they readily form adventitious roots and later spread by producing horizontal shoots. The ease with which cuttings root may not warrant the development of micropropagation procedures to clone existing cultivars. However, micropropagation technology can aid in cranberry improvement because it would allow for the rapid increase of desirable bud sports, seedlings derived from breeding programs, or genetically engineered plants. If virus-indexed for publication 4 Sept. 1990. Publication no. 3016 of the Massachuricultural Experiment Station. This research was supported in part by assistance and equipment donations from Ocean Spray Cranberries, are grateful for the cooperation of Jack Crooks. The cost of publishing r was defrayed in part by the payment of page charges. Under postal ns, this paper therefore must be hereby marked advertisement solely