(50(2):67-77)Study on the Mutation in Lycoris aurea via Chemical Mutagen Treatment

本試驗利用金花石蒜生長點所誘發不定芽的芽原體為材料，以Ethy1 methane sulfonate (EMS)，秋水仙素，5-Azacytidine (azaC) 為處理之藥劑，於86年12月進行不同濃度及不同時間的誘變處理，條件如下：0.05、0.5、5、50Mm azaC 處理一天；0.1、0.2、0.5% EMS 處理一小時以及0.1、0.2%秋水仙素各處理一天與四天；接著於89年5月進行以0.05、0.1、0.2%秋水仙素處理芽原體1、2、4天之另一誘變試驗。在86年12月試驗，組培苗再生與變異比例結果發現，誘變處理一個月後，組培苗之再生率以0.5mM azaC 處理一天為最高 (52%)，0.2% 秋水仙素處理一天最低 (2.5%)；將存活之誘變組培苗，進行外表性狀調查，發現部份具有葉基部白化、葉捲曲、葉片粗厚等現象，各處理均有超過50%的可視變異機率，以50mM azaC 與0.2%秋水仙素處理一天最高（超過90%），對照組（未經誘變處理者）亦有5% 的可視體細胞變異。金花石蒜因生育緩慢，自播種至開花約需5-6年，組培苗出瓶後於溫室栽培，亦需約4-5年才可達開花階段，花朵變異部分需較長時間才能進行篩選。現階段先進行誘變株的染色體觀察，結果發現大部分受測單株的染色體數符合2n = 2x = 14，然89年5月處理秋水仙素部分，則有鑲嵌倍數體 (polidy chimeras) 的現象，且細胞間多倍體的比例較二倍體高。另外，誘變組培苗健化出瓶之性狀調查，於田間網室發現在0.5mM azaC 一天處理者有葉色鑲嵌與全葉呈淡黃綠色之葉色變異單株。因此，對照染色體數不變，單株葉色產生變異之情形下，推測誘變處理可能引致染色體內基因組的變異。Lycoris aurea is an important native tuberous flowering plant in Taiwan. People are favorably impressed with its noble and attractive flowers. Unfortunately, owing to less genetic variability, L. aurea has only little color diversities and almost only one unique flower type can be seen in the market. We are trying to solve this problem through artificial mutagenesis. In December 1997, we treated bud primordia of in vitro shoot with chemical mutagens, including 5-azacytidine (5-Ac), ethyl methane sulfonate (EMS), and colchicine. The various concentrations and exposure duration were used including one day immersion separately in 0.05, 0.5, 5, and 50mM 5-azacytidine; one hour treatment in 0.1, 0.2, or 0.5% EMS suspension; and 0.1 and 0.2% colchicine separately for one and four days exposure. Besides we repeated the cochicine treatments (0.05, 0.1, 0.2% colchicine for 1, 2, 4 days immersion) in May 2000. In this study we found an increase of the concentrations of various chemical mutagens along with a greater toxicity and lethality in the mutagen-treated explants. The highest regeneration ratio (52%) was found in 0.5 mM azaC for 1-day treatment and the lowest ratio (2.5%) was found in 0.2% colchicine for 1-day treatment in the former experiment one month after treatments. The major phenotypic variations appeared in cultured mutant including etiolated leaves base, curve and thicken leaves. The variation ratio of cultured mutant were over 50% for all treatments, even the CK (without any chemical treatment) also has 5% somaclonal variation. Mutants with variegated and etiolated leaves were found in 0.5mM azaC for 1-day treatment after transplanting to field. No differences in chromosome number (2n = 2x = 14) in the former experiment were found however a ploidy chimeras were found in the later experiment (such as 2n = l0x - 2 = 68 in 0.2% colchicine for 4 days treatment). According to the cytological data, it revealed that something changed in genomic DNA level. The morphological changes on flower color and types have not yet collected since it took 4 - 5 years for growing the flowering bulbs. We hope that using this approach the efficiency of variety improvement on L. aurea could significantly enhance, therefore benefiting the development of the L. aurea industry