The Chromosomes of Hemerocallis (Liliaceae)

Abstract

Hemerocallis L. (day lily) of the family Liliaceae is now estimated to have 14 (Chen 1980) to 21 (Hu 1968b) species. Its natural distribution area is China, Japan, Korea, Mongolia, Siberia, the easternmost parts of the Soviet Union, and northern India. H. lilio-asphodelus and H.fulva were brought from Asia to Europe some time before the mid-16th century. Other species were discovered and introduced to Europe, North America and other parts of the world from the mid-18th century onwards (Hu 1968a). In the West numerous cultivars have been bred through hybridization and colchicine treatment, and are widely grown as ornamentals. In China H. citrina and some other species have been utilized since ancient times and many cultivars of H. citrina have been selected and maintained (Chen 1980). They are grown mainly for their flower buds which, after being collected, steamed and dried, are sold in the market for use in cooking as a delicacy. Their roots are used as medicinal herbs (Hu 1968c). Chromosome numbers of most species and many cultivars have been counted previously. Among them, H. aurantiaca and H.fulva and their varieties were reported to be either diploid (2n = 22) or triploid (2n = 33) or both, by the same or different authors, while most other species were found to be diploid only (2n = 22). Polyploidy higher than the triploid level has not been found in nature, but artificially induced tetraploid cultivars have been reported (Traub 1951, Peck & Arisumi 1968). Although many chromosome counts have been published, descriptions of their karyotypes, if given, are not always accurate, detailed or comparable. Several classifications of Hemerocallis chromosomes have been proposed, using various features and standards. Some authors made little attempt to subdivide the karyotypes into homologous pairs and triplets (Dark 1932, Sat6 1942, Takenaka 1952, Kawano 1961, Vij et al. 1978); others (e.g. Matsuoka 1971) saw and illustrated homologues but classified some of the chromosomes as unique with no obvious homologue and others as groups of four or more. Publications with detailed chromosome drawings or good quality microphotographs are relatively few (Matsuoka 1971, Terasaka & Tanaka 1974a, Vij et al. 1978, Noguchi & Tanaka 1981), so a study was made of the karyotypes of a collection of species and one hybrid growing at the Royal Botanic Gardens, Kew, in order to augment our knowledge of the chromosomes of this genus.