Micropropagation of the Endangered Shrub Pondberry (Lindera melissifolia

A micropropagation protocol using shoot cultures is described for Lindera meli$sifolia, a federally listed endangered shrub endemic to the southeastern United States. Stock plants were harvested from native L. melissifolia populations growing in the lower Mississippi Alluvial Valley. In vitro proliferation was on woody plant medium supplemented with 1 prvz zeatin. After 6 weeks, zeatin level was increased to 5 )11~. Treatment of micropropagated shoots with a liquid auxin (2 indole-3-butyric acid : 1 1naphthalenacetic acid) resulted in a low mean rooting percentage (144%) compared with rooting in the absence of auxins and on a pure peat medium ex vitro, which increased rooting to 280%. Time to rooting was 8 weeks. Plants were acclimatized for 2 weeks, then potted in a 2 peat : 1 perlite medium supplemented with superphosphate, ION-1OP-lOK, and Milorganite. Micropropagated L. meliss~~olia stecklings have been successfully outplanted in both controlled and field studies at the Center for Bottomland Hardwoods Research (Stoneville, Miss.). Micropropagation has proven to be useful in research and conservation of endangered plant species. In efforts to sustain naturally occurring populations, micropropagation has been used to maintain and restore genetic diversity (Godt et al., 1997; Hammatt and Evans, 1985; Machon et al., 2001) and supplement populations in their native habitat (Anand and Rao, 2000; Jamison and Renfi.oe, 1998). Furthermore, micropropagation provides a means of mass producing plants, thereby relieving harvesting pressure on those species of economic importance (Negash, 2002; Rai, 2002; Rosas et al., Received for publication 10 Aug. 2006. Accepted for publication 12 Oct. 2006. We thank Ben Ware, Stephanie Skojac, and Bryce Burke for their assistance during field collection; U.S. Fish and Wildlife Service for collection permits; the U.S. Army Corps of Engineers for underwriting some of the cost of this research, and Craig Echt and Brian Lockhart for critical reviews of an earlier draft of this manuscript. Mention of a trademark, proprietary product, or vendor does not constitute a guarantee or warranty of the product by the U.S. Department of Agriculture and does not imply its approval to the exclusion of other products or vendors that also may be suitable. 'To whom reprint requests should be addressed; e-mail [email protected] 2001; Rubluo et al., 1993). In the United States, federal policy restricts reintroduction of propagated plants as a recovery strategy unless all other methods to improve a listed species status have failed, or have proved to be ineffective (U.S. Fish and Wildlife Service, 2000). However, federal policy does allow propagation of endangered plant species for purposes of scientific research. In 2002, the Center for Bottomland Hardwoods Research (CBHR) began conducting extensive, multidisciplinary research on Lindera melissifolia, a federally endangered shrub (US. Fish and Wildlife Service, 1986) endemic to the southeastern United States. Of special concern were L. melissifolia populations growing in periodically flooded bottomland forests in the Mississippi Delta of the Lower Mississippi Alluvial Valley (LMAV). The LMAV has been described as one of the most endangered ecosystems in the United States (Noss et a]., 1995), primarily affected by agriculture and changes in hydrologic cycles Erom flood control projects (Stanturf et al., 2000). In light of the potential for future anthropogenic disturbance in this physiographic region, and in keeping with the pondberry recovery plan (U.S. Fish and Wildlife Service, 1993), a need exists for an understanding of life history attributes of L. rnelissifolia and development of management practices that will ensure the sustainability of native populations. In order for CBHR to carry out pondberry research, it was necessary that 1) acquisition of large quantities of plants did not create a severe harvesting impact on naturally occurring pondberry populations, 2) plants used in the research process represented a reasonable cross-section of genotypes fiom the Mississippi Delta, and 3) upon initiation of some studies, plants be of the same physiological age -and of reasonably uniform size. It was decided that micropropagation would be the best alternative for satisfying these criteria. Therefore, the objective of this initial investigation was to establish a protocol for micropropagation of L. melissifolia.