| Summary: | 碩士 === 國立屏東科技大學 === 熱帶農業暨國際合作系所 === 96 === Saintpaulia is a commercially valuable potted plant due to its diversity in leaf and flower shapes and colors. The wide range of Saintpaulia cultivars available to date were mostly derived from cross-pollination between species and from mutations that occurred during leaf cutting propagation. The aim of the present study was to investigate the potential use of the chemical mutagen ethyl methanesulfonate (EMS) in inducing mutations in Saintpaulia. Leaf sections of approximately 4 mm2 in size from in vitro grown cultures of S. cv. Crystobal were used for the EMS experiment. The explants were treated with 0.2, 0.4 and 0.6% EMS for 30, 60, 120 and 240 minutes. The percentage of explant survival and shooting capacity was recorded 4 and 8 weeks following the treatments. Explants that survived EMS treatments first showed an enlargement in size followed by the formation of shoot primordia in the subsequent weeks. No survival was recorded when explants were treated with 0.6% EMS for 120 and 240 min. It was found that explants that survived EMS treatments were all capable of forming shoots. Although a large number of shoots were regenerated following EMS treatments, a big proportion of these were lost due to the occurrence of hyperhydricity in the cultures. By discarding shoots presenting severe symptoms of hyperhydricity, shoots recovered from the EMS treatments can be successfully acclimatized ex vitro with a high survival rate (99.4% in average). Out of the 1838 plants evaluated after acclimatization, 16 plants presented morphological variations in the leaf compared to the controls. Six of these plants exhibited foliage variegation and the remaining ten plants contained leaves with a superficial brilliance. Variegated foliage plants were obtained from the 0.2% EMS treatment for 60 and 240 min, and from the 0.4% EMS treatment for 60 and 120 min. The brilliant foliage plants were derived from the 0.4% EMS treatment for 240 min, and from 0.6% EMS treatment for 30 min. The highest mutation rate of 10.7% was recorded from the 0.4% EMS treatment for 240 minutes. Continuous monitoring of plants up to the flowering stage is currently carried out in order to identify any flower-specific variations, as well as the adaptability of the plants to high or low temperatures. The findings in the present study demonstrated that 0.2-0.6% EMS was useful in inducing mutations in Saintpaulia leaves. Upon the improvement of the in vitro culture environment which caused hyperhydricity, the EMS system reported here may open a new route for breeding new Saintpaulia varieties.
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