Practical Sugar-Free Micropropagation System Using Large Vessels with Forced Ventilation

Abstract

Conventional micropropagation systems using sugar-containing medium under low light intensity and ambient CO₂ concentration are widely used for mass-production of plantlets. However, problems such as high % contamination, poor growth and development of plantlets, low % survival at ex vitro acclimatization and high production costs are limiting further commercial use of micropropagation. Our objective in the present study was to develop a practical photoautotrophic (sugar-free in the medium) micropropagation system using a large culture vessel with forced ventilation under high light intensity and CO₂ concentration. Expiants excised from potato (Solanum tuberosum L. cv. Benimaru) and statice (Limonium latifolium) plantlets were cultured in sterilized large (125 L) and small (380 mL) vessels. Large vessels with forced ventilation, containing sugar-free perlite as supporting material, and small vessels with natural ventilation, containing sugar-free agar as supporting material, were placed at photosynthetic photon flux (PPF) of ca.120 μmol m^-2 s^-1 and CO₂ concentration of ca. 1,500 μmol mol^-1. Small vessels with sugar-containing agar medium were also placed at PPF of ca. 40 μmol m^-2 s^-1 and CO₂ concentration of ca.370 μmol mol^-1 as the conventional method. The results showed that the photoautotrophic micropropagation system using the large vessel at CO₂ concentration ca. 1,500 μmol mol^-1 gave the greatest fresh weight, dry weight and leaf area of potato and statice plantlets, and that it gave the highest % survival of 95% after transplanting ex vitro and the highest plantlet quality among the three treatments. This photoautotrophic micropropagation system with forced ventilation has been used for commercial micropropagation of economically important potato and statice plantlets in Kunming, China since 1997, based on the results shown above. The production costs was decreased by about 50% compared with the costs in the conventional method. The average price could be increased by 40%, due to the high quality, compared with the price of plantlets produced in the conventional method, resulting in a great economical profit. This photoautotrophic micropropagation system has an extensive application and will improve the protocol for micropropagation with use of chlorophyllous expiants for many plant species in the forthcoming decades.