Propagule Type and Planting Time for Field-established Mayapple

INTRODUCTION The American mayapple (Podophyllum peltatum L.; Berberidaceae) is a rhizomatous perennial species found throughout eastern North America. The species has received attention recently due to pharmaceutical compounds found in its leaves. Podophyllotoxin, along with α-peltatin, and β-peltatin, are aryltetralin lignans known to have biological activity such as anti-cancer, anti-fungal, anti-viral, anti-mitotic, and immunostimulatory properties (Rahman et al. 1995; Goel et al. 1998; Imbert 1998; Pugh et al. 2001). Podophyllotoxin is also used as a precursor in the semi-synthesis of etoposide, teniposide, and etopophos, three drugs used in chemotherapy (Stähelin and von Wartburg 1991; Giri and Narasu 2000). Podophyllotoxin is currently available from the Indian mayapple [(Podophyllum emodi Wall., Berberidaceae (syn. P. hexandrum Royle)], a species native to specific regions of the Himalayas. Rhizomes and roots of the Indian mayapple contain up to 53.5 mg⋅g podophyllotoxin on a dry weight basis compared to 14.7 mg⋅g for rhizomes of the American mayapple. However, leaves of the American mayapple contain up to 55.9 mg⋅g podophyllotoxin on a dry weight basis (Canel et al. 2001; Moraes et al. 2001). Because leaves are a renewable resource, it may be possible to establish commercial plantings of this species. Rhizomes could be left undisturbed while leaves could be harvested annually. In addition, commercial plantings could reduce harvest pressure on the Indian species, which was declared endangered due to over-exploitation of wild populations (Foster 1993; Nautiyal 1996; Giri and Narasu 2000; Rai et al. 2000). It has been shown that podophyllotoxin content in leaves of American mayapple is highly variable, and some wild populations have very low content. Wildcrafting (that is, harvesting of plant materials from wild populations) would lead to inconsistent results and possibly poor drug yield (Bastos et al. 1996; Moraes et al. 2001). Commercial plantings, in contrast, would rely on selection and propagation of clonal populations with high podophyllotoxin content. Successful propagation of American mayapple using in vitro techniques has been reported (Sadowska et al. 1997; Moraes-Cerdeira et al. 1998), but most reports of vegetative propagation of Podophyllum species have been limited to the Indian mayapple. Results have been highly variable using rhizome cuttings. From 34% to 98% of rhizome cuttings 2.0 to 2.5 cm in length and planted from May to July in India were successful in establishing plants (Badhwar and Sharma 1963; Choudhary et al. 1998). Nadeem et al. (2000) found 70% of rhizome cuttings treated with 100 μM IBA produced roots compared to only 30% for untreated cuttings. Troup (1915) estimated that plants grown from rhizome cuttings would require 12 years to attain marketable size. Rhizome structure of American mayapple is distinctly different from that of the Indian mayapple. Reports about vegetative propagation of American mayapple were not found; therefore, the purpose of research presented in this report was to identify types of rhizome cuttings suitable for establishing plantings of American mayapple under field conditions. In addition, the purpose was to compare fall versus spring planting.