Effects of X-ray and electron beam irradiation on adventitious bud regeneration from in vitro leaf explants of Saintpaulia ionahta

Adventitious buds from in vitro leaf explants of two different Saintpaulia ionahta (Mauve and Indikon) cultivars were irradiated with X-rays or 9 MeV electron beams, the tissue increase, buds differentiation and leaf morphology changes were studied. The results showed that the fresh weight of leaf explants of Mauve and Indikon irradiated to 40 Gy with the X-rays increased by 27.3 and 26.3 times, whereas they increased by 49.7 and 27.4 times with the E-beam irradiation of the same dose. Changes of fresh weight increase of explants irradiated to less than 20 Gy by both X-rays and electron beams demonstrated a tendency of going down first and then increasing, which differed from those irradiated to higher than 20 Gy. The percentage of bud formation of Mauve and Indikon irradiated to 100 Gy with the electron beams were 3.7% and 11.3%, respectively, while they were 7.5% and 64.1% with the X-ray irradiation of the same dose. The percentage of plantlets with malformed leaves in Mauve irradiated with 60 Gy E-beam irradiation was 22.2%, while it was 14.8% with X-ray irradiation of the same dose. For Saintpaulia ionahta Indikon with 40 Gy E-beam irradiation, the percentage was 35.2%, whereas it was 5.8% for X-ray irradiation of the same dose. The results show that the effect of mutation induction by the electron beam irradiation on Saintpaulia ionahta is better than by the X-ray irradiation. An optimal mutagenic treatment is 40-60 Gy irradiation with the electron beams. (authors)