Micropropagation and regeneration of Ulmus parvifolia Pathfinder, the Chinese elm tree

Abstract: Micropropagation and regeneration systems were established for the U.S. National Arboretum accession, Ulmus parvifolia ‘Pathfinder’. Experiments were done using two lines of U. parvifolia, P-6 and P-10, each derived from a different, open-pollinated seed. Because micropropagation of U. parvifolia required the addition of a cytokinin to the Driver and Kuniyuki Walnut (DKW) medium, BA, mT, and TDZ were compared. Stem cuttings cultured on DKW containing 2.4 mg L^-1mT for line P-10 or 4.8 mg L^-1 mT for both lines P-6 and P-10 produced a significantly higher number of axillary shoots than cuttings on DKW lacking phytohormones. Stem cuttings on TDZ (0.25, 0.50, or 1.0 mg L^-1) produced a significantly lower number of axillary shoots. Axillary shoots of line P-6 formed roots at a low frequency (6 %) as compared to those of P-10 shoots (58 %) when cultured on DKW with either NAA (1.0 mg L^-1) or IBA (1.0 mg L^-1). Most of the shoots, 96 % of P-6 and 99 % of P-10, survived in soil in the greenhouse. Shoots were regenerated from leaves taken from in vitro-grown plants, and most of the regenerated shoots came from leaves of line P-10 and very few from line P-6. P-10 leaves cultured on DKW containing 7.2 mg L^-1mT regenerated significantly more plants than leaves cultured on DKW lacking hormones. The frequency of regenerated shoots from leaves cultured on DKW with mT(2.4, 4.8, or 7.2 mg L^-1) that formed roots in vitro was 47, and 98 % of the shoots survived in soil in the greenhouse. This study indicates the benefit of using mT for micro propagation and regeneration from leaves of U. parvifolia.