Mass-propagation of Virus-free Plants of Japanese Butterbur (Petasites japonicus Fr. Schmidt), by Tissue Culture

Abstract

The vegetative propagation rate of Japanese butterbur plants is low, it often permits four viruses to be transmitted to the next generation through the rhizomes as in other vegetatively propagated crops. All of the butterbur plants in the field are eventually inflicted with viruses. The purpose of this study is to establish an efficient masspropagation system of virus-free plants by tissue culture.
Shoots from flower-heads were induced on Murashige and Skoog's (MS) solid medium containing 0.1 mg•liter^-1 NAA and 1.0mg•liter^-1 BA. After 12 weeks of culture, 5.2 shoots per explant were obtained from 80% of the flower-heads.
Rapid clonal propagules were obtained when 2-cm shoots were transferred to MS liquid medium supplemented with 0.01mg•liter^-1 NAA and 3.0mg•liter^-1 BA and placed on a gyrating, rotary shaker set at 100 rpm. After 8 weeks of culture, 80.9 shoots from axillary buds were obtained. These shoots rooted remarkably well in half-strength B 5 liquid medium without phytohormones while being gyrated.
All regenerated plants became acclimated readily when grown in a sandy loam at 25°C.
Although no cucumber mosaic virus (CMV) or butterbur mosaic virus (BuMV) was detected in the plants, 8.1% were infected with arabis mosaic virus (ArMV). Thus, 91.9% of the regenerated plants were virus-free.
These results indicate that this micropropagation system of using flower-heads and axillary buds seems adaptable for a large-scale system of supplying virus-free Japanese butterbur plants.