Development of micropropagation methods of shallot (Allium cepa var. ascalonicum Backer)

Abstract

Shallot is a foreign crop introduced from France in 1995 as a new overwintering field crop with a aim to develop into an export crop. During the introductory cultivation trials, several problems were raised such as premature growth depression in early summer, sensitivity to summer moisture, and weakened vigor of the seed bulbs following successive propagations. This study was conducted to suggest cultural and propagational solutions to these problems. Genetically stable plantlets were obtained by the basal plate culture. Floral organ culture was considered as a good method because it produced plantlets with multiple shoots after 30 days in culture. However, more time was required for bulblet formation than in the disc culture. It took 140 days to obtain seed bulblets in the basal plate culture, 250 days in the floral organ culture, and 320 days in the meristem culture. Total number of days taken for micropropagation in the basal plate culture was 56% and 44% of that in the floral organ culture and meristem culture, respectively. On the contrary, the speed of propagation of the floral organ culture was 4 to 13 times as high as that of the basal plate culture. To summarize, meristem culture was good for obtaining virus-free bulbs, but was limited by a long culture period and a low propagation speed.