LAUSR

Abstract Ultraviolet-C (UV-C) radiation is well-known for its germicidal effect but its mutagenic potential in aiding new plant variety development has not been explored extensively. Persian violet (Exacum affine Balf.f. ex Regel) is a well-known decorative plant in Thailand. In this research, the effects of 0–4 h of UV-C irradiation on shoot proliferation and in vitro flowering of Persian violet plantlets derived from non-encapsulated and encapsulated microshoots were investigated. The number of multiple shoots was found to decrease as UV-C exposure time increased. Shoot-tip decapitation increased floral number in plantlets derived from both non-capsulated and encapsulated microshoots. The plantlets developed from non-encapsulated microshoots exposed to 4 h of UV-C irradiation exhibited tiny flower buds within 3 days from shoot-tip decapitation of the plantlets. However, the time for flower initiation was 35 days in control plantlets developed from non-encapsulated microshoots without irradiation. Another interesting novel finding is that 4 h of UV-C irradiation of the non-encapsulated microshoots resulted in the highest number of flowers (6.80 flowers) in the plantlets after 10 weeks compared to all the other treatments including the control that had only 3.20 flowers. This finding of Persian violet flowers with 7 petals has never been reported before. However, this UV-C treatment of the non-encapsulated microshoots diminished viability and in vitro germinability of pollen more than those in the treatment of encapsulated microshoots. Thus, UV-C irradiation of Persian violet microshoots affected multiple shoot proliferation and in vitro flowering. Encapsulation of the microshoots could counteract many of these effects of UV-C irradiation.