Regeneration of Plants from Protoplasts of Hemerocallis (Daylily)

Abstract

Daylilies (Hemerocallis species and cultivars) are herbaceous perennials much sought after for their showy, albeit very short-lived, blooms. The genus has traditionally been classified in the family Liliaceae but now is placed in the Hemerocallidaceae comprising a single genus and some 14 or 15 species (Dahlgren et al. 1985). The family is endemic to the temperate regions of Asia, but ranges from eastern and southern Europe to northern, eastern, and central China, to Korea and Japan. Hemerocallis assumes the gross habit of other clump-forming perennial monocotyledons. The mature plant is composed of fans (ramets) which consist of an underground stem (rhizome), roots, leaves, and a flowering scape. The crown of the plant, referred to horticulturally as the vegetative stem or rootstock, sometimes and erroneously called a pseudobulb, produces long, strap-shaped leaves above andfibrous roots below. Axillary buds may grow or remain dormant and can be forced to yield vegetative separations. The crown is said to be slowly pulled into the ground with continued contractile root growth (Wilkins 1985). An expansive fibrous or fibrous-tuberous root system anchors the plant. The foliage, which may be deciduous or evergreen, consists of sheathed-at-the-base, heavily ribbed leaves which when mature (Fitter and Krikorian 1985; Smith et al. 1989) are long and two-ranked (distichous). Flowers are borne on afloral stalk or scape which is often branched and largely leafless but with some leaf-like bracts, and shoot propagules called proliferations. The number of flower buds per scape may vary (approx. 5 to 12). Flowers are hypogynous, trimerous (3+3 petaloid) and basally connate into a tube; tepals may be apically recurved. Theflowers are perfect and fairly large and last only 1 day (Bielski and Reid 1992). The plants are genetically heterozygous and hence seedlings must be raised to maturity before their qualities are assessable. This generally takes 3-4 years for varieties that are “fast” and longer for those that are “slow”. When a plant with a desirable phenotype is obtained, it is invariably multiplied vegetatively so as to fix the genotype.