Comparative morphological and transcriptome in two Lycoris species

Ms. Ziming Ren is a PhD student at Zhejiang University working in ornamental horticulture. The objective of her thesis is to explore the mechanisms regulating the formation and development of bulblets (vegetative propagation) of Lycoris spp. Lycoris is a genus of flowering bulbs of high medicinal and ornamental value belonging to the Amaryllidaceae. This genus consists of about 20 native species that are distributed in Eastern Asia. Lycoris has shade tolerance and a wide range of flower colors, which has recently increased its popularity as flowering ground cover. Wild harvests of these plants have dramatically increased to fill the market demand, and consequently the species has become threatened. Breeding and commercial production of Lycoris have been hindered by a long sexual reproduction cycle and low regeneration rate under natural conditions. The objective of this study was to estimate the vegetative propagation from bulb scales by performing morphological and transcriptome evaluation. Flowering-sized bulbs of Lycoris sprengeri and Lycoris aurea (two major landscaping species used in the Yangtze River region of China) were selected and their sizes were measured. Under containerized conditions, with no growth regulators, L. sprengeri showed a greater ability to form bulblets (ca. 1-5 bulblets/bulb section) than L. aurea (ca. 1-2 bulblets/bulb section). Axillary meristems on the abaxial side of the scale base were initiated during the early stages of vegetative reproduction. Many small cells with dense cytoplasm were observed in the rapidly growing meristems, which give rise to the axillary buds. Basal scale tissues connecting to the plate were collected for transcriptome analysis from the beginning of the multiplication process (0 h, 6 h, 48 h, 6 d, 15 d, 27 d and 36 d). Most of the differentially expressed genes (DEGs) were gathered in the very early stage (6 h from the excision of the bulb scale) for both species. For L. sprengeri, a higher number of ethylene-related DEGs were found compared to the value recorded for L. aurea. This is consistent with previous findings in Lilium where the number of adventitious buds formed on bulb scale explants increased with the application of ethylene. Ethylene might integrate the signals of wounding and changes in polar auxin transport. Thus, our studies led us to determine that the vegetative propagation depends on the number of newly formed meristems on the explant. Their outgrowth enables the formation of a new axillary bud. Our results suggested that ethylene plays a part during axillary meristems development in Lycoris. From these promising results, we hope to enhance the multiplication efficiency in Lycoris.

Ms. Ziming Ren won an ISHS Young Minds Award for the best oral presentation at the the XIII International Symposium on Flower Bulbs and Herbaceous Perennials in Korea in May 2019.

Ms. Ziming Ren, Department of Horticulture, College of Agriculture and Biotechnology, Zhejiang University, Zhejiang, Hangzhou, 310058, P.R. China, e-mail: zimingren@zju.edu.cn

The article is available in Chronica Horticulturae